diff --git a/src/harness/client.ts b/src/harness/client.ts
index c040ee60ae58c..32db9e92a7a17 100644
--- a/src/harness/client.ts
+++ b/src/harness/client.ts
@@ -825,6 +825,22 @@ namespace ts.server {
             return notImplemented();
         }
 
+        toggleLineComment(): TextChange[] {
+            return notImplemented();
+        }
+
+        toggleMultilineComment(): TextChange[] {
+            return notImplemented();
+        }
+
+        commentSelection(): TextChange[] {
+            return notImplemented();
+        }
+
+        uncommentSelection(): TextChange[] {
+            return notImplemented();
+        }
+
         dispose(): void {
             throw new Error("dispose is not available through the server layer.");
         }
diff --git a/src/harness/fourslashImpl.ts b/src/harness/fourslashImpl.ts
index ca95ff34ebb72..283a1d3c93d93 100644
--- a/src/harness/fourslashImpl.ts
+++ b/src/harness/fourslashImpl.ts
@@ -3189,7 +3189,7 @@ namespace FourSlash {
 
                 this.raiseError(
                     `Expected to find a fix with the name '${fixName}', but none exists.` +
-                    availableFixes.length
+                        availableFixes.length
                         ? ` Available fixes: ${availableFixes.map(fix => `${fix.fixName} (${fix.fixId ? "with" : "without"} fix-all)`).join(", ")}`
                         : ""
                 );
@@ -3428,13 +3428,13 @@ namespace FourSlash {
 
             const incomingCalls =
                 direction === CallHierarchyItemDirection.Outgoing ? { result: "skip" } as const :
-                alreadySeen ? { result: "seen" } as const :
-                { result: "show", values: this.languageService.provideCallHierarchyIncomingCalls(callHierarchyItem.file, callHierarchyItem.selectionSpan.start) } as const;
+                    alreadySeen ? { result: "seen" } as const :
+                        { result: "show", values: this.languageService.provideCallHierarchyIncomingCalls(callHierarchyItem.file, callHierarchyItem.selectionSpan.start) } as const;
 
             const outgoingCalls =
                 direction === CallHierarchyItemDirection.Incoming ? { result: "skip" } as const :
-                alreadySeen ? { result: "seen" } as const :
-                { result: "show", values: this.languageService.provideCallHierarchyOutgoingCalls(callHierarchyItem.file, callHierarchyItem.selectionSpan.start) } as const;
+                    alreadySeen ? { result: "seen" } as const :
+                        { result: "show", values: this.languageService.provideCallHierarchyOutgoingCalls(callHierarchyItem.file, callHierarchyItem.selectionSpan.start) } as const;
 
             let text = "";
             text += `${prefix}╭ name: ${callHierarchyItem.name}\n`;
@@ -3448,7 +3448,7 @@ namespace FourSlash {
             text += `${prefix}├ selectionSpan:\n`;
             text += this.formatCallHierarchyItemSpan(file, callHierarchyItem.selectionSpan, `${prefix}│ `,
                 incomingCalls.result !== "skip" || outgoingCalls.result !== "skip" ? `${prefix}│ ` :
-                `${trailingPrefix}╰ `);
+                    `${trailingPrefix}╰ `);
 
             if (incomingCalls.result === "seen") {
                 if (outgoingCalls.result === "skip") {
@@ -3477,8 +3477,8 @@ namespace FourSlash {
                         text += `${prefix}│ ├ fromSpans:\n`;
                         text += this.formatCallHierarchyItemSpans(file, incomingCall.fromSpans, `${prefix}│ │ `,
                             i < incomingCalls.values.length - 1 ? `${prefix}│ ╰ ` :
-                            outgoingCalls.result !== "skip" ? `${prefix}│ ╰ ` :
-                            `${trailingPrefix}╰ ╰ `);
+                                outgoingCalls.result !== "skip" ? `${prefix}│ ╰ ` :
+                                    `${trailingPrefix}╰ ╰ `);
                     }
                 }
             }
@@ -3499,7 +3499,7 @@ namespace FourSlash {
                         text += `${prefix}│ ├ fromSpans:\n`;
                         text += this.formatCallHierarchyItemSpans(file, outgoingCall.fromSpans, `${prefix}│ │ `,
                             i < outgoingCalls.values.length - 1 ? `${prefix}│ ╰ ` :
-                            `${trailingPrefix}╰ ╰ `);
+                                `${trailingPrefix}╰ ╰ `);
                     }
                 }
             }
@@ -3659,6 +3659,50 @@ namespace FourSlash {
         public configurePlugin(pluginName: string, configuration: any): void {
             (<ts.server.SessionClient>this.languageService).configurePlugin(pluginName, configuration);
         }
+
+        public toggleLineComment(newFileContent: string): void {
+            const changes: ts.TextChange[] = [];
+            for (const range of this.getRanges()) {
+                changes.push.apply(changes, this.languageService.toggleLineComment(this.activeFile.fileName, range));
+            }
+
+            this.applyEdits(this.activeFile.fileName, changes);
+
+            this.verifyCurrentFileContent(newFileContent);
+        }
+
+        public toggleMultilineComment(newFileContent: string): void {
+            const changes: ts.TextChange[] = [];
+            for (const range of this.getRanges()) {
+                changes.push.apply(changes, this.languageService.toggleMultilineComment(this.activeFile.fileName, range));
+            }
+
+            this.applyEdits(this.activeFile.fileName, changes);
+
+            this.verifyCurrentFileContent(newFileContent);
+        }
+
+        public commentSelection(newFileContent: string): void {
+            const changes: ts.TextChange[] = [];
+            for (const range of this.getRanges()) {
+                changes.push.apply(changes, this.languageService.commentSelection(this.activeFile.fileName, range));
+            }
+
+            this.applyEdits(this.activeFile.fileName, changes);
+
+            this.verifyCurrentFileContent(newFileContent);
+        }
+
+        public uncommentSelection(newFileContent: string): void {
+            const changes: ts.TextChange[] = [];
+            for (const range of this.getRanges()) {
+                changes.push.apply(changes, this.languageService.uncommentSelection(this.activeFile.fileName, range));
+            }
+
+            this.applyEdits(this.activeFile.fileName, changes);
+
+            this.verifyCurrentFileContent(newFileContent);
+        }
     }
 
     function prefixMessage(message: string | undefined) {
diff --git a/src/harness/fourslashInterfaceImpl.ts b/src/harness/fourslashInterfaceImpl.ts
index dcbd07b4dbf09..c23a4ac801f95 100644
--- a/src/harness/fourslashInterfaceImpl.ts
+++ b/src/harness/fourslashInterfaceImpl.ts
@@ -214,6 +214,22 @@ namespace FourSlashInterface {
         public refactorAvailableForTriggerReason(triggerReason: ts.RefactorTriggerReason, name: string, actionName?: string) {
             this.state.verifyRefactorAvailable(this.negative, triggerReason, name, actionName);
         }
+
+        public toggleLineComment(newFileContent: string) {
+            this.state.toggleLineComment(newFileContent);
+        }
+
+        public toggleMultilineComment(newFileContent: string) {
+            this.state.toggleMultilineComment(newFileContent);
+        }
+
+        public commentSelection(newFileContent: string) {
+            this.state.commentSelection(newFileContent);
+        }
+
+        public uncommentSelection(newFileContent: string) {
+            this.state.uncommentSelection(newFileContent);
+        }
     }
 
     export class Verify extends VerifyNegatable {
diff --git a/src/harness/harnessLanguageService.ts b/src/harness/harnessLanguageService.ts
index bc3c738a6b8c6..6c3ee40eee068 100644
--- a/src/harness/harnessLanguageService.ts
+++ b/src/harness/harnessLanguageService.ts
@@ -603,6 +603,18 @@ namespace Harness.LanguageService {
         clearSourceMapperCache(): never {
             return ts.notImplemented();
         }
+        toggleLineComment(fileName: string, textRange: ts.TextRange): ts.TextChange[] {
+            return unwrapJSONCallResult(this.shim.toggleLineComment(fileName, textRange));
+        }
+        toggleMultilineComment(fileName: string, textRange: ts.TextRange): ts.TextChange[] {
+            return unwrapJSONCallResult(this.shim.toggleMultilineComment(fileName, textRange));
+        }
+        commentSelection(fileName: string, textRange: ts.TextRange): ts.TextChange[] {
+            return unwrapJSONCallResult(this.shim.commentSelection(fileName, textRange));
+        }
+        uncommentSelection(fileName: string, textRange: ts.TextRange): ts.TextChange[] {
+            return unwrapJSONCallResult(this.shim.uncommentSelection(fileName, textRange));
+        }
         dispose(): void { this.shim.dispose({}); }
     }
 
diff --git a/src/server/protocol.ts b/src/server/protocol.ts
index de974058fa167..cdeaad1a4fc22 100644
--- a/src/server/protocol.ts
+++ b/src/server/protocol.ts
@@ -136,7 +136,18 @@ namespace ts.server.protocol {
         SelectionRange = "selectionRange",
         /* @internal */
         SelectionRangeFull = "selectionRange-full",
-
+        ToggleLineComment = "toggleLineComment",
+        /* @internal */
+        ToggleLineCommentFull = "toggleLineComment-full",
+        ToggleMultilineComment = "toggleMultilineComment",
+        /* @internal */
+        ToggleMultilineCommentFull = "toggleMultilineComment-full",
+        CommentSelection = "commentSelection",
+        /* @internal */
+        CommentSelectionFull = "commentSelection-full",
+        UncommentSelection = "uncommentSelection",
+        /* @internal */
+        UncommentSelectionFull = "uncommentSelection-full",
         PrepareCallHierarchy = "prepareCallHierarchy",
         ProvideCallHierarchyIncomingCalls = "provideCallHierarchyIncomingCalls",
         ProvideCallHierarchyOutgoingCalls = "provideCallHierarchyOutgoingCalls",
@@ -1542,6 +1553,26 @@ namespace ts.server.protocol {
         parent?: SelectionRange;
     }
 
+    export interface ToggleLineCommentRequest extends FileRequest {
+        command: CommandTypes.ToggleLineComment;
+        arguments: FileRangeRequestArgs;
+    }
+
+    export interface ToggleMultilineCommentRequest extends FileRequest {
+        command: CommandTypes.ToggleMultilineComment;
+        arguments: FileRangeRequestArgs;
+    }
+
+    export interface CommentSelectionRequest extends FileRequest {
+        command: CommandTypes.CommentSelection;
+        arguments: FileRangeRequestArgs;
+    }
+
+    export interface UncommentSelectionRequest extends FileRequest {
+        command: CommandTypes.UncommentSelection;
+        arguments: FileRangeRequestArgs;
+    }
+
     /**
      *  Information found in an "open" request.
      */
diff --git a/src/server/session.ts b/src/server/session.ts
index d8c35c7924c2a..c559fb8faa989 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -2012,8 +2012,7 @@ namespace ts.server {
                 position = getPosition(args);
             }
             else {
-                const { startPosition, endPosition } = this.getStartAndEndPosition(args, scriptInfo);
-                textRange = { pos: startPosition, end: endPosition };
+                textRange = this.getRange(args, scriptInfo);
             }
             return Debug.checkDefined(position === undefined ? textRange : position);
 
@@ -2022,6 +2021,12 @@ namespace ts.server {
             }
         }
 
+        private getRange(args: protocol.FileRangeRequestArgs, scriptInfo: ScriptInfo): TextRange {
+            const { startPosition, endPosition } = this.getStartAndEndPosition(args, scriptInfo);
+
+            return { pos: startPosition, end: endPosition };
+        }
+
         private getApplicableRefactors(args: protocol.GetApplicableRefactorsRequestArgs): protocol.ApplicableRefactorInfo[] {
             const { file, project } = this.getFileAndProject(args);
             const scriptInfo = project.getScriptInfoForNormalizedPath(file)!;
@@ -2251,6 +2256,70 @@ namespace ts.server {
             });
         }
 
+        private toggleLineComment(args: protocol.FileRangeRequestArgs, simplifiedResult: boolean): TextChange[] | protocol.CodeEdit[] {
+            const { file, languageService } = this.getFileAndLanguageServiceForSyntacticOperation(args);
+            const scriptInfo = this.projectService.getScriptInfo(file)!;
+            const textRange = this.getRange(args, scriptInfo);
+
+            const textChanges = languageService.toggleLineComment(file, textRange);
+
+            if (simplifiedResult) {
+                const scriptInfo = this.projectService.getScriptInfoForNormalizedPath(file)!;
+
+                return textChanges.map(textChange => this.convertTextChangeToCodeEdit(textChange, scriptInfo));
+            }
+
+            return textChanges;
+        }
+
+        private toggleMultilineComment(args: protocol.FileRangeRequestArgs, simplifiedResult: boolean): TextChange[] | protocol.CodeEdit[] {
+            const { file, languageService } = this.getFileAndLanguageServiceForSyntacticOperation(args);
+            const scriptInfo = this.projectService.getScriptInfoForNormalizedPath(file)!;
+            const textRange = this.getRange(args, scriptInfo);
+
+            const textChanges = languageService.toggleMultilineComment(file, textRange);
+
+            if (simplifiedResult) {
+                const scriptInfo = this.projectService.getScriptInfoForNormalizedPath(file)!;
+
+                return textChanges.map(textChange => this.convertTextChangeToCodeEdit(textChange, scriptInfo));
+            }
+
+            return textChanges;
+        }
+
+        private commentSelection(args: protocol.FileRangeRequestArgs, simplifiedResult: boolean): TextChange[] | protocol.CodeEdit[] {
+            const { file, languageService } = this.getFileAndLanguageServiceForSyntacticOperation(args);
+            const scriptInfo = this.projectService.getScriptInfoForNormalizedPath(file)!;
+            const textRange = this.getRange(args, scriptInfo);
+
+            const textChanges = languageService.commentSelection(file, textRange);
+
+            if (simplifiedResult) {
+                const scriptInfo = this.projectService.getScriptInfoForNormalizedPath(file)!;
+
+                return textChanges.map(textChange => this.convertTextChangeToCodeEdit(textChange, scriptInfo));
+            }
+
+            return textChanges;
+        }
+
+        private uncommentSelection(args: protocol.FileRangeRequestArgs, simplifiedResult: boolean): TextChange[] | protocol.CodeEdit[] {
+            const { file, languageService } = this.getFileAndLanguageServiceForSyntacticOperation(args);
+            const scriptInfo = this.projectService.getScriptInfoForNormalizedPath(file)!;
+            const textRange = this.getRange(args, scriptInfo);
+
+            const textChanges = languageService.uncommentSelection(file, textRange);
+
+            if (simplifiedResult) {
+                const scriptInfo = this.projectService.getScriptInfoForNormalizedPath(file)!;
+
+                return textChanges.map(textChange => this.convertTextChangeToCodeEdit(textChange, scriptInfo));
+            }
+
+            return textChanges;
+        }
+
         private mapSelectionRange(selectionRange: SelectionRange, scriptInfo: ScriptInfo): protocol.SelectionRange {
             const result: protocol.SelectionRange = {
                 textSpan: toProtocolTextSpan(selectionRange.textSpan, scriptInfo),
@@ -2697,6 +2766,30 @@ namespace ts.server {
             [CommandNames.ProvideCallHierarchyOutgoingCalls]: (request: protocol.ProvideCallHierarchyOutgoingCallsRequest) => {
                 return this.requiredResponse(this.provideCallHierarchyOutgoingCalls(request.arguments));
             },
+            [CommandNames.ToggleLineComment]: (request: protocol.ToggleLineCommentRequest) => {
+                return this.requiredResponse(this.toggleLineComment(request.arguments, /*simplifiedResult*/ true));
+            },
+            [CommandNames.ToggleLineCommentFull]: (request: protocol.ToggleLineCommentRequest) => {
+                return this.requiredResponse(this.toggleLineComment(request.arguments, /*simplifiedResult*/ false));
+            },
+            [CommandNames.ToggleMultilineComment]: (request: protocol.ToggleMultilineCommentRequest) => {
+                return this.requiredResponse(this.toggleMultilineComment(request.arguments, /*simplifiedResult*/ true));
+            },
+            [CommandNames.ToggleMultilineCommentFull]: (request: protocol.ToggleMultilineCommentRequest) => {
+                return this.requiredResponse(this.toggleMultilineComment(request.arguments, /*simplifiedResult*/ false));
+            },
+            [CommandNames.CommentSelection]: (request: protocol.CommentSelectionRequest) => {
+                return this.requiredResponse(this.commentSelection(request.arguments, /*simplifiedResult*/ true));
+            },
+            [CommandNames.CommentSelectionFull]: (request: protocol.CommentSelectionRequest) => {
+                return this.requiredResponse(this.commentSelection(request.arguments, /*simplifiedResult*/ false));
+            },
+            [CommandNames.UncommentSelection]: (request: protocol.UncommentSelectionRequest) => {
+                return this.requiredResponse(this.uncommentSelection(request.arguments, /*simplifiedResult*/ true));
+            },
+            [CommandNames.UncommentSelectionFull]: (request: protocol.UncommentSelectionRequest) => {
+                return this.requiredResponse(this.uncommentSelection(request.arguments, /*simplifiedResult*/ false));
+            },
         }));
 
         public addProtocolHandler(command: string, handler: (request: protocol.Request) => HandlerResponse) {
diff --git a/src/services/services.ts b/src/services/services.ts
index eb1e9659648de..fa0f02a9b95df 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -5,8 +5,8 @@ namespace ts {
     function createNode<TKind extends SyntaxKind>(kind: TKind, pos: number, end: number, parent: Node): NodeObject | TokenObject<TKind> | IdentifierObject | PrivateIdentifierObject {
         const node = isNodeKind(kind) ? new NodeObject(kind, pos, end) :
             kind === SyntaxKind.Identifier ? new IdentifierObject(SyntaxKind.Identifier, pos, end) :
-            kind === SyntaxKind.PrivateIdentifier ? new PrivateIdentifierObject(SyntaxKind.PrivateIdentifier, pos, end) :
-                new TokenObject(kind, pos, end);
+                kind === SyntaxKind.PrivateIdentifier ? new PrivateIdentifierObject(SyntaxKind.PrivateIdentifier, pos, end) :
+                    new TokenObject(kind, pos, end);
         node.parent = parent;
         node.flags = parent.flags & NodeFlags.ContextFlags;
         return node;
@@ -773,7 +773,7 @@ namespace ts {
                         if (!hasSyntacticModifier(node, ModifierFlags.ParameterPropertyModifier)) {
                             break;
                         }
-                        // falls through
+                    // falls through
 
                     case SyntaxKind.VariableDeclaration:
                     case SyntaxKind.BindingElement: {
@@ -834,7 +834,7 @@ namespace ts {
                         if (getAssignmentDeclarationKind(node as BinaryExpression) !== AssignmentDeclarationKind.None) {
                             addDeclaration(node as BinaryExpression);
                         }
-                        // falls through
+                    // falls through
 
                     default:
                         forEachChild(node, visit);
@@ -1994,6 +1994,236 @@ namespace ts {
             }
         }
 
+        function getLinesForRange(sourceFile: SourceFile, textRange: TextRange) {
+            return {
+                lineStarts: sourceFile.getLineStarts(),
+                firstLine: sourceFile.getLineAndCharacterOfPosition(textRange.pos).line,
+                lastLine: sourceFile.getLineAndCharacterOfPosition(textRange.end).line
+            };
+        }
+
+        function toggleLineComment(fileName: string, textRange: TextRange, insertComment?: boolean): TextChange[] {
+            const sourceFile = syntaxTreeCache.getCurrentSourceFile(fileName);
+            const textChanges: TextChange[] = [];
+            const { lineStarts, firstLine, lastLine } = getLinesForRange(sourceFile, textRange);
+
+            let isCommenting = insertComment || false;
+            let leftMostPosition = Number.MAX_VALUE;
+            const lineTextStarts = new Map<string, number>();
+            const firstNonWhitespaceCharacterRegex = new RegExp(/\S/);
+            const isJsx = isInsideJsxElement(sourceFile, lineStarts[firstLine]);
+            const openComment = isJsx ? "{/*" : "//";
+
+            // Check each line before any text changes.
+            for (let i = firstLine; i <= lastLine; i++) {
+                const lineText = sourceFile.text.substring(lineStarts[i], sourceFile.getLineEndOfPosition(lineStarts[i]));
+
+                // Find the start of text and the left-most character. No-op on empty lines.
+                const regExec = firstNonWhitespaceCharacterRegex.exec(lineText);
+                if (regExec) {
+                    leftMostPosition = Math.min(leftMostPosition, regExec.index);
+                    lineTextStarts.set(i.toString(), regExec.index);
+
+                    if (lineText.substr(regExec.index, openComment.length) !== openComment) {
+                        isCommenting = insertComment === undefined || insertComment;
+                    }
+                }
+            }
+
+            // Push all text changes.
+            for (let i = firstLine; i <= lastLine; i++) {
+                const lineTextStart = lineTextStarts.get(i.toString());
+
+                // If the line is not an empty line; otherwise no-op.
+                if (lineTextStart !== undefined) {
+                    if (isJsx) {
+                        textChanges.push.apply(textChanges, toggleMultilineComment(fileName, { pos: lineStarts[i] + leftMostPosition, end: sourceFile.getLineEndOfPosition(lineStarts[i]) }, isCommenting, isJsx));
+                    }
+                    else if (isCommenting) {
+                        textChanges.push({
+                            newText: openComment,
+                            span: {
+                                length: 0,
+                                start: lineStarts[i] + leftMostPosition
+                            }
+                        });
+                    }
+                    else if (sourceFile.text.substr(lineStarts[i] + lineTextStart, openComment.length) === openComment) {
+                        textChanges.push({
+                            newText: "",
+                            span: {
+                                length: openComment.length,
+                                start: lineStarts[i] + lineTextStart
+                            }
+                        });
+                    }
+                }
+            }
+
+            return textChanges;
+        }
+
+        function toggleMultilineComment(fileName: string, textRange: TextRange, insertComment?: boolean, isInsideJsx?: boolean): TextChange[] {
+            const sourceFile = syntaxTreeCache.getCurrentSourceFile(fileName);
+            const textChanges: TextChange[] = [];
+            const { text } = sourceFile;
+
+            let hasComment = false;
+            let isCommenting = insertComment || false;
+            const positions = [] as number[] as SortedArray<number>;
+
+            let { pos } = textRange;
+            const isJsx = isInsideJsx !== undefined ? isInsideJsx : isInsideJsxElement(sourceFile, pos);
+
+            const openMultiline = isJsx ? "{/*" : "/*";
+            const closeMultiline = isJsx ? "*/}" : "*/";
+            const openMultilineRegex = isJsx ? "\\{\\/\\*" : "\\/\\*";
+            const closeMultilineRegex = isJsx ? "\\*\\/\\}" : "\\*\\/";
+
+            // Get all comment positions
+            while (pos <= textRange.end) {
+                // Start of comment is considered inside comment.
+                const offset = text.substr(pos, openMultiline.length) === openMultiline ? openMultiline.length : 0;
+                const commentRange = isInComment(sourceFile, pos + offset);
+
+                // If position is in a comment add it to the positions array.
+                if (commentRange) {
+                    // Comment range doesn't include the brace character. Increase it to include them.
+                    if (isJsx) {
+                        commentRange.pos--;
+                        commentRange.end++;
+                    }
+
+                    positions.push(commentRange.pos);
+                    if (commentRange.kind === SyntaxKind.MultiLineCommentTrivia) {
+                        positions.push(commentRange.end);
+                    }
+
+                    hasComment = true;
+                    pos = commentRange.end + 1;
+                }
+                else { // If it's not in a comment range, then we need to comment the uncommented portions.
+                    const newPos = text.substring(pos, textRange.end).search(`(${openMultilineRegex})|(${closeMultilineRegex})`);
+
+                    isCommenting = insertComment !== undefined
+                        ? insertComment
+                        : isCommenting || !isTextWhiteSpaceLike(text, pos, newPos === -1 ? textRange.end : pos + newPos); // If isCommenting is already true we don't need to check whitespace again.
+                    pos = newPos === -1 ? textRange.end + 1 : pos + newPos + closeMultiline.length;
+                }
+            }
+
+            // If it didn't found a comment and isCommenting is false means is only empty space.
+            // We want to insert comment in this scenario.
+            if (isCommenting || !hasComment) {
+                if (isInComment(sourceFile, textRange.pos)?.kind !== SyntaxKind.SingleLineCommentTrivia) {
+                    insertSorted(positions, textRange.pos, compareValues);
+                }
+                insertSorted(positions, textRange.end, compareValues);
+
+                // Insert open comment if the first position is not a comment already.
+                const firstPos = positions[0];
+                if (text.substr(firstPos, openMultiline.length) !== openMultiline) {
+                    textChanges.push({
+                        newText: openMultiline,
+                        span: {
+                            length: 0,
+                            start: firstPos
+                        }
+                    });
+                }
+
+                // Insert open and close comment to all positions between first and last. Exclusive.
+                for (let i = 1; i < positions.length - 1; i++) {
+                    if (text.substr(positions[i] - closeMultiline.length, closeMultiline.length) !== closeMultiline) {
+                        textChanges.push({
+                            newText: closeMultiline,
+                            span: {
+                                length: 0,
+                                start: positions[i]
+                            }
+                        });
+                    }
+
+                    if (text.substr(positions[i], openMultiline.length) !== openMultiline) {
+                        textChanges.push({
+                            newText: openMultiline,
+                            span: {
+                                length: 0,
+                                start: positions[i]
+                            }
+                        });
+                    }
+                }
+
+                // Insert open comment if the last position is not a comment already.
+                if (textChanges.length % 2 !== 0) {
+                    textChanges.push({
+                        newText: closeMultiline,
+                        span: {
+                            length: 0,
+                            start: positions[positions.length - 1]
+                        }
+                    });
+                }
+            }
+            else {
+                // If is not commenting then remove all comments found.
+                for (const pos of positions) {
+                    const from = pos - closeMultiline.length > 0 ? pos - closeMultiline.length : 0;
+                    const offset = text.substr(from, closeMultiline.length) === closeMultiline ? closeMultiline.length : 0;
+                    textChanges.push({
+                        newText: "",
+                        span: {
+                            length: openMultiline.length,
+                            start: pos - offset
+                        }
+                    });
+                }
+            }
+
+            return textChanges;
+        }
+
+        function commentSelection(fileName: string, textRange: TextRange): TextChange[] {
+            const sourceFile = syntaxTreeCache.getCurrentSourceFile(fileName);
+            const { firstLine, lastLine } = getLinesForRange(sourceFile, textRange);
+
+            // If there is a selection that is on the same line, add multiline.
+            return firstLine === lastLine && textRange.pos !== textRange.end
+                ? toggleMultilineComment(fileName, textRange, /*insertComment*/ true)
+                : toggleLineComment(fileName, textRange, /*insertComment*/ true);
+        }
+
+        function uncommentSelection(fileName: string, textRange: TextRange): TextChange[] {
+            const sourceFile = syntaxTreeCache.getCurrentSourceFile(fileName);
+            const textChanges: TextChange[] = [];
+            const { pos } = textRange;
+            let { end } = textRange;
+
+            // If cursor is not a selection we need to increase the end position
+            // to include the start of the comment.
+            if (pos === end) {
+                end += isInsideJsxElement(sourceFile, pos) ? 2 : 1;
+            }
+
+            for (let i = pos; i <= end; i++) {
+                const commentRange = isInComment(sourceFile, i);
+                if (commentRange) {
+                    switch (commentRange.kind) {
+                        case SyntaxKind.SingleLineCommentTrivia:
+                            textChanges.push.apply(textChanges, toggleLineComment(fileName, { end: commentRange.end, pos: commentRange.pos + 1 }, /*insertComment*/ false));
+                            break;
+                        case SyntaxKind.MultiLineCommentTrivia:
+                            textChanges.push.apply(textChanges, toggleMultilineComment(fileName, { end: commentRange.end, pos: commentRange.pos + 1 }, /*insertComment*/ false));
+                    }
+
+                    i = commentRange.end + 1;
+                }
+            }
+
+            return textChanges;
+        }
+
         function isUnclosedTag({ openingElement, closingElement, parent }: JsxElement): boolean {
             return !tagNamesAreEquivalent(openingElement.tagName, closingElement.tagName) ||
                 isJsxElement(parent) && tagNamesAreEquivalent(openingElement.tagName, parent.openingElement.tagName) && isUnclosedTag(parent);
@@ -2274,7 +2504,11 @@ namespace ts {
             clearSourceMapperCache: () => sourceMapper.clearCache(),
             prepareCallHierarchy,
             provideCallHierarchyIncomingCalls,
-            provideCallHierarchyOutgoingCalls
+            provideCallHierarchyOutgoingCalls,
+            toggleLineComment,
+            toggleMultilineComment,
+            commentSelection,
+            uncommentSelection,
         };
 
         if (syntaxOnly) {
@@ -2348,7 +2582,7 @@ namespace ts {
                 if (node.parent.kind === SyntaxKind.ComputedPropertyName) {
                     return isObjectLiteralElement(node.parent.parent) ? node.parent.parent : undefined;
                 }
-                // falls through
+            // falls through
 
             case SyntaxKind.Identifier:
                 return isObjectLiteralElement(node.parent) &&
diff --git a/src/services/shims.ts b/src/services/shims.ts
index c8149620b8c6e..8729ce6cc0bb6 100644
--- a/src/services/shims.ts
+++ b/src/services/shims.ts
@@ -277,6 +277,11 @@ namespace ts {
 
         getEmitOutput(fileName: string): string;
         getEmitOutputObject(fileName: string): EmitOutput;
+
+        toggleLineComment(fileName: string, textChange: TextRange): string;
+        toggleMultilineComment(fileName: string, textChange: TextRange): string;
+        commentSelection(fileName: string, textChange: TextRange): string;
+        uncommentSelection(fileName: string, textChange: TextRange): string;
     }
 
     export interface ClassifierShim extends Shim {
@@ -1068,6 +1073,34 @@ namespace ts {
                 () => this.languageService.getEmitOutput(fileName),
                 this.logPerformance) as EmitOutput;
         }
+
+        public toggleLineComment(fileName: string, textRange: TextRange): string {
+            return this.forwardJSONCall(
+                `toggleLineComment('${fileName}', '${JSON.stringify(textRange)}')`,
+                () => this.languageService.toggleLineComment(fileName, textRange)
+            );
+        }
+
+        public toggleMultilineComment(fileName: string, textRange: TextRange): string {
+            return this.forwardJSONCall(
+                `toggleMultilineComment('${fileName}', '${JSON.stringify(textRange)}')`,
+                () => this.languageService.toggleMultilineComment(fileName, textRange)
+            );
+        }
+
+        public commentSelection(fileName: string, textRange: TextRange): string {
+            return this.forwardJSONCall(
+                `commentSelection('${fileName}', '${JSON.stringify(textRange)}')`,
+                () => this.languageService.commentSelection(fileName, textRange)
+            );
+        }
+
+        public uncommentSelection(fileName: string, textRange: TextRange): string {
+            return this.forwardJSONCall(
+                `uncommentSelection('${fileName}', '${JSON.stringify(textRange)}')`,
+                () => this.languageService.uncommentSelection(fileName, textRange)
+            );
+        }
     }
 
     function convertClassifications(classifications: Classifications): { spans: string, endOfLineState: EndOfLineState } {
diff --git a/src/services/types.ts b/src/services/types.ts
index 5ccf5f49d4a89..73080249abdbb 100644
--- a/src/services/types.ts
+++ b/src/services/types.ts
@@ -506,6 +506,11 @@ namespace ts {
         /* @internal */ getNonBoundSourceFile(fileName: string): SourceFile;
         /* @internal */ getAutoImportProvider(): Program | undefined;
 
+        toggleLineComment(fileName: string, textRange: TextRange): TextChange[];
+        toggleMultilineComment(fileName: string, textRange: TextRange): TextChange[];
+        commentSelection(fileName: string, textRange: TextRange): TextChange[];
+        uncommentSelection(fileName: string, textRange: TextRange): TextChange[];
+
         dispose(): void;
     }
 
diff --git a/src/services/utilities.ts b/src/services/utilities.ts
index d89a68c96edbd..4c841278f42d4 100644
--- a/src/services/utilities.ts
+++ b/src/services/utilities.ts
@@ -394,7 +394,7 @@ namespace ts {
             case SyntaxKind.MethodSignature:
                 return ScriptElementKind.memberFunctionElement;
             case SyntaxKind.PropertyAssignment:
-                const {initializer} = node as PropertyAssignment;
+                const { initializer } = node as PropertyAssignment;
                 return isFunctionLike(initializer) ? ScriptElementKind.memberFunctionElement : ScriptElementKind.memberVariableElement;
             case SyntaxKind.PropertyDeclaration:
             case SyntaxKind.PropertySignature:
@@ -557,7 +557,7 @@ namespace ts {
                 if (!(<NewExpression>n).arguments) {
                     return true;
                 }
-                // falls through
+            // falls through
 
             case SyntaxKind.CallExpression:
             case SyntaxKind.ParenthesizedExpression:
@@ -877,14 +877,14 @@ namespace ts {
         // specially by `getSymbolAtLocation`.
         if (isModifier(node) && (forRename || node.kind !== SyntaxKind.DefaultKeyword) ? contains(parent.modifiers, node) :
             node.kind === SyntaxKind.ClassKeyword ? isClassDeclaration(parent) || isClassExpression(node) :
-            node.kind === SyntaxKind.FunctionKeyword ? isFunctionDeclaration(parent) || isFunctionExpression(node) :
-            node.kind === SyntaxKind.InterfaceKeyword ? isInterfaceDeclaration(parent) :
-            node.kind === SyntaxKind.EnumKeyword ? isEnumDeclaration(parent) :
-            node.kind === SyntaxKind.TypeKeyword ? isTypeAliasDeclaration(parent) :
-            node.kind === SyntaxKind.NamespaceKeyword || node.kind === SyntaxKind.ModuleKeyword ? isModuleDeclaration(parent) :
-            node.kind === SyntaxKind.ImportKeyword ? isImportEqualsDeclaration(parent) :
-            node.kind === SyntaxKind.GetKeyword ? isGetAccessorDeclaration(parent) :
-            node.kind === SyntaxKind.SetKeyword && isSetAccessorDeclaration(parent)) {
+                node.kind === SyntaxKind.FunctionKeyword ? isFunctionDeclaration(parent) || isFunctionExpression(node) :
+                    node.kind === SyntaxKind.InterfaceKeyword ? isInterfaceDeclaration(parent) :
+                        node.kind === SyntaxKind.EnumKeyword ? isEnumDeclaration(parent) :
+                            node.kind === SyntaxKind.TypeKeyword ? isTypeAliasDeclaration(parent) :
+                                node.kind === SyntaxKind.NamespaceKeyword || node.kind === SyntaxKind.ModuleKeyword ? isModuleDeclaration(parent) :
+                                    node.kind === SyntaxKind.ImportKeyword ? isImportEqualsDeclaration(parent) :
+                                        node.kind === SyntaxKind.GetKeyword ? isGetAccessorDeclaration(parent) :
+                                            node.kind === SyntaxKind.SetKeyword && isSetAccessorDeclaration(parent)) {
             const location = getAdjustedLocationForDeclaration(parent, forRename);
             if (location) {
                 return location;
@@ -1320,6 +1320,35 @@ namespace ts {
         return false;
     }
 
+    export function isInsideJsxElement(sourceFile: SourceFile, position: number): boolean {
+        function isInsideJsxElementTraversal(node: Node): boolean {
+            while (node) {
+                if (node.kind >= SyntaxKind.JsxSelfClosingElement && node.kind <= SyntaxKind.JsxExpression
+                    || node.kind === SyntaxKind.JsxText
+                    || node.kind === SyntaxKind.LessThanToken
+                    || node.kind === SyntaxKind.GreaterThanToken
+                    || node.kind === SyntaxKind.Identifier
+                    || node.kind === SyntaxKind.CloseBraceToken
+                    || node.kind === SyntaxKind.OpenBraceToken
+                    || node.kind === SyntaxKind.SlashToken) {
+                    node = node.parent;
+                }
+                else if (node.kind === SyntaxKind.JsxElement) {
+                    if (position > node.getStart(sourceFile)) return true;
+
+                    node = node.parent;
+                }
+                else {
+                    return false;
+                }
+            }
+
+            return false;
+        }
+
+        return isInsideJsxElementTraversal(getTokenAtPosition(sourceFile, position));
+    }
+
     export function findPrecedingMatchingToken(token: Node, matchingTokenKind: SyntaxKind, sourceFile: SourceFile) {
         const tokenKind = token.kind;
         let remainingMatchingTokens = 0;
@@ -1346,7 +1375,7 @@ namespace ts {
     export function removeOptionality(type: Type, isOptionalExpression: boolean, isOptionalChain: boolean) {
         return isOptionalExpression ? type.getNonNullableType() :
             isOptionalChain ? type.getNonOptionalType() :
-            type;
+                type;
     }
 
     export function isPossiblyTypeArgumentPosition(token: Node, sourceFile: SourceFile, checker: TypeChecker): boolean {
@@ -1439,7 +1468,7 @@ namespace ts {
                     break;
 
                 case SyntaxKind.EqualsGreaterThanToken:
-                    // falls through
+                // falls through
 
                 case SyntaxKind.Identifier:
                 case SyntaxKind.StringLiteral:
@@ -1447,7 +1476,7 @@ namespace ts {
                 case SyntaxKind.BigIntLiteral:
                 case SyntaxKind.TrueKeyword:
                 case SyntaxKind.FalseKeyword:
-                    // falls through
+                // falls through
 
                 case SyntaxKind.TypeOfKeyword:
                 case SyntaxKind.ExtendsKeyword:
@@ -1934,6 +1963,16 @@ namespace ts {
         return undefined;
     }
 
+    export function isTextWhiteSpaceLike(text: string, startPos: number, endPos: number): boolean {
+        for (let i = startPos; i < endPos; i++) {
+            if (!isWhiteSpaceLike(text.charCodeAt(i))) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
     // #endregion
 
     // Display-part writer helpers
@@ -2242,8 +2281,8 @@ namespace ts {
             // This only happens for leaf nodes - internal nodes always see their children change.
             const clone =
                 isStringLiteral(node) ? setOriginalNode(factory.createStringLiteralFromNode(node), node) as Node as T :
-                isNumericLiteral(node) ? setOriginalNode(factory.createNumericLiteral(node.text, node.numericLiteralFlags), node) as Node as T :
-                factory.cloneNode(node);
+                    isNumericLiteral(node) ? setOriginalNode(factory.createNumericLiteral(node.text, node.numericLiteralFlags), node) as Node as T :
+                        factory.cloneNode(node);
             return setTextRange(clone, node);
         }
 
diff --git a/src/testRunner/unittests/tsserver/session.ts b/src/testRunner/unittests/tsserver/session.ts
index 7a144945340fa..8084b79056b30 100644
--- a/src/testRunner/unittests/tsserver/session.ts
+++ b/src/testRunner/unittests/tsserver/session.ts
@@ -272,6 +272,10 @@ namespace ts.server {
                 CommandNames.PrepareCallHierarchy,
                 CommandNames.ProvideCallHierarchyIncomingCalls,
                 CommandNames.ProvideCallHierarchyOutgoingCalls,
+                CommandNames.ToggleLineComment,
+                CommandNames.ToggleMultilineComment,
+                CommandNames.CommentSelection,
+                CommandNames.UncommentSelection,
             ];
 
             it("should not throw when commands are executed with invalid arguments", () => {
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index c0a87752b8cb4..8442b93e4f686 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -5487,6 +5487,10 @@ declare namespace ts {
         getEditsForFileRename(oldFilePath: string, newFilePath: string, formatOptions: FormatCodeSettings, preferences: UserPreferences | undefined): readonly FileTextChanges[];
         getEmitOutput(fileName: string, emitOnlyDtsFiles?: boolean, forceDtsEmit?: boolean): EmitOutput;
         getProgram(): Program | undefined;
+        toggleLineComment(fileName: string, textRange: TextRange): TextChange[];
+        toggleMultilineComment(fileName: string, textRange: TextRange): TextChange[];
+        commentSelection(fileName: string, textRange: TextRange): TextChange[];
+        uncommentSelection(fileName: string, textRange: TextRange): TextChange[];
         dispose(): void;
     }
     interface JsxClosingTagInfo {
@@ -6482,6 +6486,10 @@ declare namespace ts.server.protocol {
         GetEditsForFileRename = "getEditsForFileRename",
         ConfigurePlugin = "configurePlugin",
         SelectionRange = "selectionRange",
+        ToggleLineComment = "toggleLineComment",
+        ToggleMultilineComment = "toggleMultilineComment",
+        CommentSelection = "commentSelection",
+        UncommentSelection = "uncommentSelection",
         PrepareCallHierarchy = "prepareCallHierarchy",
         ProvideCallHierarchyIncomingCalls = "provideCallHierarchyIncomingCalls",
         ProvideCallHierarchyOutgoingCalls = "provideCallHierarchyOutgoingCalls"
@@ -7514,6 +7522,22 @@ declare namespace ts.server.protocol {
         textSpan: TextSpan;
         parent?: SelectionRange;
     }
+    interface ToggleLineCommentRequest extends FileRequest {
+        command: CommandTypes.ToggleLineComment;
+        arguments: FileRangeRequestArgs;
+    }
+    interface ToggleMultilineCommentRequest extends FileRequest {
+        command: CommandTypes.ToggleMultilineComment;
+        arguments: FileRangeRequestArgs;
+    }
+    interface CommentSelectionRequest extends FileRequest {
+        command: CommandTypes.CommentSelection;
+        arguments: FileRangeRequestArgs;
+    }
+    interface UncommentSelectionRequest extends FileRequest {
+        command: CommandTypes.UncommentSelection;
+        arguments: FileRangeRequestArgs;
+    }
     /**
      *  Information found in an "open" request.
      */
@@ -9870,6 +9894,7 @@ declare namespace ts.server {
         private getSupportedCodeFixes;
         private isLocation;
         private extractPositionOrRange;
+        private getRange;
         private getApplicableRefactors;
         private getEditsForRefactor;
         private organizeImports;
@@ -9887,6 +9912,10 @@ declare namespace ts.server {
         private getDiagnosticsForProject;
         private configurePlugin;
         private getSmartSelectionRange;
+        private toggleLineComment;
+        private toggleMultilineComment;
+        private commentSelection;
+        private uncommentSelection;
         private mapSelectionRange;
         private getScriptInfoFromProjectService;
         private toProtocolCallHierarchyItem;
diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
index 9a549e1ffa4af..3f7f682342456 100644
--- a/tests/baselines/reference/api/typescript.d.ts
+++ b/tests/baselines/reference/api/typescript.d.ts
@@ -5487,6 +5487,10 @@ declare namespace ts {
         getEditsForFileRename(oldFilePath: string, newFilePath: string, formatOptions: FormatCodeSettings, preferences: UserPreferences | undefined): readonly FileTextChanges[];
         getEmitOutput(fileName: string, emitOnlyDtsFiles?: boolean, forceDtsEmit?: boolean): EmitOutput;
         getProgram(): Program | undefined;
+        toggleLineComment(fileName: string, textRange: TextRange): TextChange[];
+        toggleMultilineComment(fileName: string, textRange: TextRange): TextChange[];
+        commentSelection(fileName: string, textRange: TextRange): TextChange[];
+        uncommentSelection(fileName: string, textRange: TextRange): TextChange[];
         dispose(): void;
     }
     interface JsxClosingTagInfo {
diff --git a/tests/cases/fourslash/commentSelection1.ts b/tests/cases/fourslash/commentSelection1.ts
new file mode 100644
index 0000000000000..d5a7846395594
--- /dev/null
+++ b/tests/cases/fourslash/commentSelection1.ts
@@ -0,0 +1,26 @@
+// Simple comment selection cases.
+
+//// let var1[| = 1;
+//// let var2 = 2;
+//// let var3 |]= 3;
+//// 
+//// let var4[| = 4;|]
+//// 
+//// let [||]var5 = 5;
+//// 
+//// //let var6[| = 6;
+//// //let var7 = 7;
+//// //let var8 |]= 8;
+
+verify.commentSelection(
+    `//let var1 = 1;
+//let var2 = 2;
+//let var3 = 3;
+
+let var4/* = 4;*/
+
+//let var5 = 5;
+
+////let var6 = 6;
+////let var7 = 7;
+////let var8 = 8;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/commentSelection2.ts b/tests/cases/fourslash/commentSelection2.ts
new file mode 100644
index 0000000000000..31c56a60a2bb4
--- /dev/null
+++ b/tests/cases/fourslash/commentSelection2.ts
@@ -0,0 +1,29 @@
+// Common jsx insert comment.
+
+//@Filename: file.tsx
+//// const a = <MyContainer>
+////     [|<MyFirstComponent />
+////     <MySecondComponent />|]
+//// </MyContainer>;
+//// const b = <MyContainer>
+////     {/*<MyF[|irstComponent />*/}
+////     {/*<MySec|]ondComponent />*/}
+//// </MyContainer>;
+//// const c = <MyContainer>[|
+////     <MyFirstComponent />
+////     <MySecondCompo|]nent />
+//// </MyContainer>;
+
+verify.commentSelection(
+    `const a = <MyContainer>
+    {/*<MyFirstComponent />*/}
+    {/*<MySecondComponent />*/}
+</MyContainer>;
+const b = <MyContainer>
+    {/*<MyFirstComponent />*/}
+    {/*<MySecondComponent />*/}
+</MyContainer>;
+//const c = <MyContainer>
+//    <MyFirstComponent />
+//    <MySecondComponent />
+</MyContainer>;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/fourslash.ts b/tests/cases/fourslash/fourslash.ts
index a2be4e57a2e0a..1b439bf64917d 100644
--- a/tests/cases/fourslash/fourslash.ts
+++ b/tests/cases/fourslash/fourslash.ts
@@ -397,6 +397,11 @@ declare namespace FourSlashInterface {
         generateTypes(...options: GenerateTypesOptions[]): void;
 
         organizeImports(newContent: string): void;
+
+        toggleLineComment(newFileContent: string): void;
+        toggleMultilineComment(newFileContent: string): void;
+        commentSelection(newFileContent: string): void;
+        uncommentSelection(newFileContent: string): void;
     }
     class edit {
         backspace(count?: number): void;
diff --git a/tests/cases/fourslash/toggleLineComment1.ts b/tests/cases/fourslash/toggleLineComment1.ts
new file mode 100644
index 0000000000000..1f72de7b40276
--- /dev/null
+++ b/tests/cases/fourslash/toggleLineComment1.ts
@@ -0,0 +1,18 @@
+// Simple comment and uncomment.
+
+//// let var1[| = 1;
+//// let var2 = 2;
+//// let var3 |]= 3;
+////
+//// //let var4[| = 1;
+//// //let var5 = 2;
+//// //let var6 |]= 3;
+
+verify.toggleLineComment(
+    `//let var1 = 1;
+//let var2 = 2;
+//let var3 = 3;
+
+let var4 = 1;
+let var5 = 2;
+let var6 = 3;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleLineComment10.ts b/tests/cases/fourslash/toggleLineComment10.ts
new file mode 100644
index 0000000000000..0f6c3d271988b
--- /dev/null
+++ b/tests/cases/fourslash/toggleLineComment10.ts
@@ -0,0 +1,11 @@
+// Close and open multiline comments if the line already contains more comments.
+
+//@Filename: file.tsx
+//// const a = <div>
+////     Som[||]e{/* T */}ext
+//// </div>;
+
+verify.toggleLineComment(
+    `const a = <div>
+    {/*Some*/}{/* T */}{/*ext*/}
+</div>;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleLineComment2.ts b/tests/cases/fourslash/toggleLineComment2.ts
new file mode 100644
index 0000000000000..710bd5ef3f7db
--- /dev/null
+++ b/tests/cases/fourslash/toggleLineComment2.ts
@@ -0,0 +1,20 @@
+// When indentation is different between lines it should get the left most indentation
+// and use that for all lines.
+// When uncommeting, doesn't matter what indentation the line has.
+
+////         let var1[| = 1;
+////     let var2 = 2;
+////             let var3 |]= 3;
+////
+//// //    let var4[| = 1;
+//// //let var5 = 2;
+//// //        let var6 |]= 3;
+
+verify.toggleLineComment(
+    `    //    let var1 = 1;
+    //let var2 = 2;
+    //        let var3 = 3;
+
+    let var4 = 1;
+let var5 = 2;
+        let var6 = 3;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleLineComment3.ts b/tests/cases/fourslash/toggleLineComment3.ts
new file mode 100644
index 0000000000000..d8f9aeabb99db
--- /dev/null
+++ b/tests/cases/fourslash/toggleLineComment3.ts
@@ -0,0 +1,26 @@
+// Comment and uncomment ignores empty lines.
+
+//// let var1[| = 1;
+////
+//// let var2 = 2;
+////
+//// let var3 |]= 3;
+////
+//// //let var4[| = 1;
+////
+//// //let var5 = 2;
+////
+//// //let var6 |]= 3;
+
+verify.toggleLineComment(
+    `//let var1 = 1;
+
+//let var2 = 2;
+
+//let var3 = 3;
+
+let var4 = 1;
+
+let var5 = 2;
+
+let var6 = 3;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleLineComment4.ts b/tests/cases/fourslash/toggleLineComment4.ts
new file mode 100644
index 0000000000000..5e4beb6070a7e
--- /dev/null
+++ b/tests/cases/fourslash/toggleLineComment4.ts
@@ -0,0 +1,18 @@
+// If at least one line is not commented then comment all lines again.
+
+////  //const a[| = 1;
+//// const b = 2
+////  //const c =|] 3;
+////
+//// ////const d[| = 4;
+//// //const e = 5;
+//// ////const e =|] 6;
+
+verify.toggleLineComment(
+    `// //const a = 1;
+//const b = 2
+// //const c = 3;
+
+//const d = 4;
+const e = 5;
+//const e = 6;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleLineComment5.ts b/tests/cases/fourslash/toggleLineComment5.ts
new file mode 100644
index 0000000000000..bec00a9233323
--- /dev/null
+++ b/tests/cases/fourslash/toggleLineComment5.ts
@@ -0,0 +1,22 @@
+// Comments inside strings are still considered comments.
+
+//// let var1 = `
+//// //some stri[|ng
+//// //some other|] string
+//// `;
+////
+//// let var2 = `
+//// some stri[|ng
+//// some other|] string
+//// `;
+
+verify.toggleLineComment(
+    `let var1 = \`
+some string
+some other string
+\`;
+
+let var2 = \`
+//some string
+//some other string
+\`;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleLineComment6.ts b/tests/cases/fourslash/toggleLineComment6.ts
new file mode 100644
index 0000000000000..4274cc18308ce
--- /dev/null
+++ b/tests/cases/fourslash/toggleLineComment6.ts
@@ -0,0 +1,15 @@
+// Selection is at the start of jsx its still js.
+
+//@Filename: file.tsx
+//// let a = (
+////     [|<div>
+////         some text|]
+////     </div>
+//// );
+
+verify.toggleLineComment(
+    `let a = (
+    //<div>
+    //    some text
+    </div>
+);`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleLineComment7.ts b/tests/cases/fourslash/toggleLineComment7.ts
new file mode 100644
index 0000000000000..5a6cbb002fbf5
--- /dev/null
+++ b/tests/cases/fourslash/toggleLineComment7.ts
@@ -0,0 +1,29 @@
+// Common comment line cases.
+
+//@Filename: file.tsx
+//// const a = <MyContainer>
+////     [|<MyFirstComponent />
+////     <MySecondComponent />|]
+//// </MyContainer>;
+//// const b = <MyContainer>
+////     {/*<MyF[|irstComponent />*/}
+////     {/*<MySec|]ondComponent />*/}
+//// </MyContainer>;
+//// const c = <MyContainer>[|
+////     <MyFirstComponent />
+////     <MySecondCompo|]nent />
+//// </MyContainer>;
+
+verify.toggleLineComment(
+    `const a = <MyContainer>
+    {/*<MyFirstComponent />*/}
+    {/*<MySecondComponent />*/}
+</MyContainer>;
+const b = <MyContainer>
+    <MyFirstComponent />
+    <MySecondComponent />
+</MyContainer>;
+//const c = <MyContainer>
+//    <MyFirstComponent />
+//    <MySecondComponent />
+</MyContainer>;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleLineComment8.ts b/tests/cases/fourslash/toggleLineComment8.ts
new file mode 100644
index 0000000000000..1c3bed3fd8eb1
--- /dev/null
+++ b/tests/cases/fourslash/toggleLineComment8.ts
@@ -0,0 +1,30 @@
+// When indentation is different between lines it should get the left most indentation
+// and use that for all lines.
+// When uncommeting, doesn't matter what indentation the line has.
+
+//@Filename: file.tsx
+//// const a = <div>
+////     [|<div>
+////         SomeText
+////     </div>|]
+//// </div>;
+////
+//// const b = <div>
+////     {/*[|<div>*/}
+////     {/*    SomeText*/}
+////     {/*</div>|]*/}
+//// </div>;
+
+
+verify.toggleLineComment(
+    `const a = <div>
+    {/*<div>*/}
+    {/*    SomeText*/}
+    {/*</div>*/}
+</div>;
+
+const b = <div>
+    <div>
+        SomeText
+    </div>
+</div>;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleLineComment9.ts b/tests/cases/fourslash/toggleLineComment9.ts
new file mode 100644
index 0000000000000..1fbaea7ea383a
--- /dev/null
+++ b/tests/cases/fourslash/toggleLineComment9.ts
@@ -0,0 +1,18 @@
+// If at least one line is not commented then comment all lines again.
+// TODO: Not sure about this one. The default behavior for line comment is to add en extra
+// layer of comments (see toggleLineComment4 test). For jsx this doesn't work right as it's actually
+// multiline comment. Figure out what to do.
+
+//@Filename: file.tsx
+//// const a = <div>
+////     {/*[|<div>*/}
+////         SomeText
+////     {/*</div>|]*/}
+//// </div>;
+
+verify.toggleLineComment(
+    `const a = <div>
+    {/*<div>*/}
+    {/*    SomeText*/}
+    {/*</div>*/}
+</div>;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleMultilineComment1.ts b/tests/cases/fourslash/toggleMultilineComment1.ts
new file mode 100644
index 0000000000000..f76e9d564734f
--- /dev/null
+++ b/tests/cases/fourslash/toggleMultilineComment1.ts
@@ -0,0 +1,30 @@
+// Simple multiline comment and uncomment.
+
+//// let var1[| = 1;
+//// let var2 = 2;
+//// let var3 |]= 3;
+////
+//// let var4/* = 1;
+//// let var5 [||]= 2;
+//// let var6 */= 3;
+////
+//// [|/*let var7 = 1;
+//// let var8 = 2;
+//// let var9 = 3;*/|]
+//// 
+//// let var10[||] = 10;
+
+verify.toggleMultilineComment(
+    `let var1/* = 1;
+let var2 = 2;
+let var3 */= 3;
+
+let var4 = 1;
+let var5 = 2;
+let var6 = 3;
+
+let var7 = 1;
+let var8 = 2;
+let var9 = 3;
+
+let var10/**/ = 10;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleMultilineComment2.ts b/tests/cases/fourslash/toggleMultilineComment2.ts
new file mode 100644
index 0000000000000..a3a8cf70f786d
--- /dev/null
+++ b/tests/cases/fourslash/toggleMultilineComment2.ts
@@ -0,0 +1,35 @@
+// If selection is outside of a multiline comment then insert comment
+// instead of removing.
+
+//// let var1/* = 1;
+//// let var2 [|= 2;
+//// let var3 */= 3;|]
+////
+//// [|let var4/* = 1;
+//// let var5 |]= 2;
+//// let var6 */= 3;
+////
+//// [|let var7/* = 1;
+//// let var8 = 2;
+//// let var9 */= 3;|]
+////
+//// /*let va[|r10 = 1;*/
+//// let var11 = 2;
+//// /*let var12|] = 3;*/
+
+verify.toggleMultilineComment(
+    `let var1/* = 1;
+let var2 *//*= 2;
+let var3 *//*= 3;*/
+
+/*let var4*//* = 1;
+let var5 *//*= 2;
+let var6 */= 3;
+
+/*let var7*//* = 1;
+let var8 = 2;
+let var9 *//*= 3;*/
+
+/*let va*//*r10 = 1;*//*
+let var11 = 2;
+*//*let var12*//* = 3;*/`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleMultilineComment3.ts b/tests/cases/fourslash/toggleMultilineComment3.ts
new file mode 100644
index 0000000000000..bcfa3418d971a
--- /dev/null
+++ b/tests/cases/fourslash/toggleMultilineComment3.ts
@@ -0,0 +1,28 @@
+/// <reference path="fourslash.ts">
+
+// If range is inside a single line comment, just add the multiline comment.
+
+//// // let va[|r1 = 1;
+//// let var2 = 2;
+//// // let var3|] = 3;
+////
+//// // let va[|r4 = 1;
+//// let var5 = 2;
+//// /* let var6|] = 3;*/
+////
+//// /* let va[|r7 = 1;*/
+//// let var8 = 2;
+//// // let var9|] = 3;
+
+verify.toggleMultilineComment(
+    `/*// let var1 = 1;
+let var2 = 2;
+// let var3*/ = 3;
+
+/*// let var4 = 1;
+let var5 = 2;
+*//* let var6*//* = 3;*/
+
+/* let va*//*r7 = 1;*//*
+let var8 = 2;
+// let var9*/ = 3;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleMultilineComment4.ts b/tests/cases/fourslash/toggleMultilineComment4.ts
new file mode 100644
index 0000000000000..216a308ae44d5
--- /dev/null
+++ b/tests/cases/fourslash/toggleMultilineComment4.ts
@@ -0,0 +1,7 @@
+// This is an edgecase. The string contains a multiline comment syntax but it is a string
+// and not actually a comment. When toggling it doesn't get escaped or appended comments.
+// The result would be a portion of the selection to be "not commented".
+
+//// /*let s[|omeLongVa*/riable = "Some other /*long th*/in|]g";
+
+verify.toggleMultilineComment(`/*let s*//*omeLongVa*//*riable = "Some other /*long th*/in*/g";`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleMultilineComment5.ts b/tests/cases/fourslash/toggleMultilineComment5.ts
new file mode 100644
index 0000000000000..0dea4ebbff44e
--- /dev/null
+++ b/tests/cases/fourslash/toggleMultilineComment5.ts
@@ -0,0 +1,34 @@
+// Jsx uses block comments for each line commented.
+
+// Common JSX comment scenarios
+
+//@Filename: file.tsx
+//// const a = <div tabIndex="0">[|</div>;|]
+//// const b = <div>This is [|valid HTML &amp;|] JSX at the same time.</div>;
+//// const c = <MyContainer>
+////     [|<MyFirstComponent />
+////     <MySecondComponent />|]
+//// </MyContainer>;
+//// const d = <MyContainer>
+////     <MyFirstComp[|onent />
+////     <MySecondComponent />|]
+//// </MyContainer>;
+//// const e = <MyComponent>[|{'foo'}|]</MyComponent>;
+//// const f = <div>Some text</div[|>;|]
+//// const g = <div>Some text<[|/div>;|]
+
+verify.toggleMultilineComment(
+    `const a = <div tabIndex="0">{/*</div>;*/}
+const b = <div>This is {/*valid HTML &amp;*/} JSX at the same time.</div>;
+const c = <MyContainer>
+    {/*<MyFirstComponent />
+    <MySecondComponent />*/}
+</MyContainer>;
+const d = <MyContainer>
+    <MyFirstComp{/*onent />
+    <MySecondComponent />*/}
+</MyContainer>;
+const e = <MyComponent>{/*{'foo'}*/}</MyComponent>;
+const f = <div>Some text</div{/*>;*/}
+const g = <div>Some text<{/*/div>;*/}`
+);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleMultilineComment6.ts b/tests/cases/fourslash/toggleMultilineComment6.ts
new file mode 100644
index 0000000000000..caa60504fd17c
--- /dev/null
+++ b/tests/cases/fourslash/toggleMultilineComment6.ts
@@ -0,0 +1,43 @@
+// Jsx uses multiline comments for each line commented.
+
+// Selection is outside of a multiline comments inserts multiline comments instead of removing.
+// There's some variations between jsx and js comments depending on the position.
+
+//@Filename: file.tsx
+//// const var1 = <div>Tex{/*t1</div>;
+//// const var2 = <div>Text2[|</div>;
+//// const var3 = <div>Tex*/}t3</div>;|]
+////
+//// [|const var4 = <div>Tex{/*t4</div>;
+//// const var5 = <div|]>Text5</div>;
+//// const var6 = <div>Tex*/}t6</div>;
+////
+//// [|const var7 = <div>Tex{/*t7</div>;
+//// const var8 = <div>Text8</div>;
+//// const var9 = <div>Tex*/}t9</div>;|]
+////
+//// const var10 = <div>
+////     {/*<div>T[|ext</div>*/}
+////     <div>Text</div>
+////     {/*<div>Text|]</div>*/}
+//// </div>;
+
+verify.toggleMultilineComment(
+    `const var1 = <div>Tex{/*t1</div>;
+const var2 = <div>Text2*/}{/*</div>;
+const var3 = <div>Tex*/}{/*t3</div>;*/}
+
+/*const var4 = <div>Tex{*//*t4</div>;
+const var5 = <div*//*>Text5</div>;
+const var6 = <div>Tex*/}t6</div>;
+
+/*const var7 = <div>Tex{*//*t7</div>;
+const var8 = <div>Text8</div>;
+const var9 = <div>Tex*//*}t9</div>;*/
+
+const var10 = <div>
+    {/*<div>T*/}{/*ext</div>*/}{/*
+    <div>Text</div>
+    */}{/*<div>Text*/}{/*</div>*/}
+</div>;`
+);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleMultilineComment7.ts b/tests/cases/fourslash/toggleMultilineComment7.ts
new file mode 100644
index 0000000000000..d4c711aee68bb
--- /dev/null
+++ b/tests/cases/fourslash/toggleMultilineComment7.ts
@@ -0,0 +1,33 @@
+// Cases where the cursor is inside JSX like sintax but it's actually js.
+
+//@Filename: file.tsx
+//// const a = (
+////     [|<div>
+////         some text|]
+////     </div>
+//// );
+//// const b = <MyComponent foo={1 [|+ 2 + 3 + 4|]} />;
+//// const c = <MyComponent message={[|'hello world'|]} />;
+//// const d = <MyTextBox autocomplete={tr[|ue|]} />;
+//// const e = <MyCo[|mponent message={'hello world'} />;|]
+//// const f = [
+////     [|<li key="A">First item</li>,
+////     <li key="B">Second item</li>,|]
+////     <li key="C">Third item</li>,
+//// ];
+
+verify.toggleMultilineComment(
+    `const a = (
+    /*<div>
+        some text*/
+    </div>
+);
+const b = <MyComponent foo={1 /*+ 2 + 3 + 4*/} />;
+const c = <MyComponent message={/*'hello world'*/} />;
+const d = <MyTextBox autocomplete={tr/*ue*/} />;
+const e = <MyCo/*mponent message={'hello world'} />;*/
+const f = [
+    /*<li key="A">First item</li>,
+    <li key="B">Second item</li>,*/
+    <li key="C">Third item</li>,
+];`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleMultilineComment8.ts b/tests/cases/fourslash/toggleMultilineComment8.ts
new file mode 100644
index 0000000000000..724c597dd0639
--- /dev/null
+++ b/tests/cases/fourslash/toggleMultilineComment8.ts
@@ -0,0 +1,12 @@
+// If the range only contains comments, uncomment all.
+
+//// /*let var[|1 = 1;*/
+//// /*let var2 = 2;*/
+//// 
+//// /*let var3 |]= 3;*/
+
+verify.toggleMultilineComment(
+    `let var1 = 1;
+let var2 = 2;
+
+let var3 = 3;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/toggleMultilineComment9.ts b/tests/cases/fourslash/toggleMultilineComment9.ts
new file mode 100644
index 0000000000000..f9761a98773d5
--- /dev/null
+++ b/tests/cases/fourslash/toggleMultilineComment9.ts
@@ -0,0 +1,30 @@
+// When there's is only whitespace, insert comment. If there is whitespace but theres a comment in bewteen, then uncomment.
+
+//// /*let var1[| = 1;*/
+////     |]
+//// 
+//// [|    
+//// /*let var2 = 2;*/|]
+//// 
+//// [|
+//// 
+//// |]
+//// 
+////     [||]
+//// 
+//// let var3[||] = 3;
+
+verify.toggleMultilineComment(
+    `let var1 = 1;
+    
+
+    
+let var2 = 2;
+
+/*
+
+*/
+
+    /**/
+
+let var3/**/ = 3;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/uncommentSelection1.ts b/tests/cases/fourslash/uncommentSelection1.ts
new file mode 100644
index 0000000000000..2245cbc2d007a
--- /dev/null
+++ b/tests/cases/fourslash/uncommentSelection1.ts
@@ -0,0 +1,42 @@
+// Simple comment selection cases.
+
+//// //let var1[| = 1;
+//// //let var2 = 2;
+//// //let var3 |]= 3;
+//// 
+//// //let var4[| = 4;
+//// /*let var5 = 5;*/
+//// //let var6 = 6;
+//// 
+//// let var7 |]= 7;
+////
+//// let var8/* = 1;
+//// let var9 [||]= 2;
+//// let var10 */= 3;
+////
+//// let var11[||]/* = 1;
+//// let var12 = 2;
+//// let var13 */= 3;
+//// 
+//// ////let var14 [||]= 14;
+
+verify.uncommentSelection(
+    `let var1 = 1;
+let var2 = 2;
+let var3 = 3;
+
+let var4 = 4;
+let var5 = 5;
+let var6 = 6;
+
+let var7 = 7;
+
+let var8 = 1;
+let var9 = 2;
+let var10 = 3;
+
+let var11 = 1;
+let var12 = 2;
+let var13 = 3;
+
+//let var14 = 14;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/uncommentSelection2.ts b/tests/cases/fourslash/uncommentSelection2.ts
new file mode 100644
index 0000000000000..745000d9c4d28
--- /dev/null
+++ b/tests/cases/fourslash/uncommentSelection2.ts
@@ -0,0 +1,34 @@
+// Common uncomment jsx cases
+
+//@Filename: file.tsx
+//// const a = <MyContainer>
+////     {/*<MyF[|irstComponent />*/}
+////     {/*<MySec|]ondComponent />*/}
+//// </MyContainer>;
+//// 
+//// const b = <div>
+////     {/*[|<div>*/}
+////         SomeText
+////     {/*</div>|]*/}
+//// </div>;
+//// 
+//// const c = <MyContainer>
+////     [||]{/*<MyFirstComponent />*/}
+//// </MyContainer>;
+
+
+verify.uncommentSelection(
+    `const a = <MyContainer>
+    <MyFirstComponent />
+    <MySecondComponent />
+</MyContainer>;
+
+const b = <div>
+    <div>
+        SomeText
+    </div>
+</div>;
+
+const c = <MyContainer>
+    <MyFirstComponent />
+</MyContainer>;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/uncommentSelection3.ts b/tests/cases/fourslash/uncommentSelection3.ts
new file mode 100644
index 0000000000000..9ad68476ceb64
--- /dev/null
+++ b/tests/cases/fourslash/uncommentSelection3.ts
@@ -0,0 +1,34 @@
+// Remove all comments within the selection
+
+//// let var1/* = 1;
+//// let var2 [|= 2;
+//// let var3 */= 3;|]
+////
+//// [|let var4/* = 1;
+//// let var5 |]= 2;
+//// let var6 */= 3;
+////
+//// [|let var7/* = 1;
+//// let var8 = 2;
+//// let var9 */= 3;|]
+////
+//// /*let va[|r10 = 1;*/
+//// let var11 = 2;
+//// /*let var12|] = 3;*/
+
+verify.uncommentSelection(
+    `let var1 = 1;
+let var2 = 2;
+let var3 = 3;
+
+let var4 = 1;
+let var5 = 2;
+let var6 = 3;
+
+let var7 = 1;
+let var8 = 2;
+let var9 = 3;
+
+let var10 = 1;
+let var11 = 2;
+let var12 = 3;`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/uncommentSelection4.ts b/tests/cases/fourslash/uncommentSelection4.ts
new file mode 100644
index 0000000000000..63faedaeddb20
--- /dev/null
+++ b/tests/cases/fourslash/uncommentSelection4.ts
@@ -0,0 +1,40 @@
+// Remove all comments in jsx.
+
+//@Filename: file.tsx
+//// const var1 = <div>Tex{/*t1</div>;
+//// const var2 = <div>Text2[|</div>;
+//// const var3 = <div>Tex*/}t3</div>;|]
+////
+//// [|const var4 = <div>Tex{/*t4</div>;
+//// const var5 = <div|]>Text5</div>;
+//// const var6 = <div>Tex*/}t6</div>;
+////
+//// [|const var7 = <div>Tex{/*t7</div>;
+//// const var8 = <div>Text8</div>;
+//// const var9 = <div>Tex*/}t9</div>;|]
+////
+//// const var10 = <div>
+////     {/*<div>T[|ext</div>*/}
+////     <div>Text</div>
+////     {/*<div>Text|]</div>*/}
+//// </div>;
+
+verify.uncommentSelection(
+    `const var1 = <div>Text1</div>;
+const var2 = <div>Text2</div>;
+const var3 = <div>Text3</div>;
+
+const var4 = <div>Text4</div>;
+const var5 = <div>Text5</div>;
+const var6 = <div>Text6</div>;
+
+const var7 = <div>Text7</div>;
+const var8 = <div>Text8</div>;
+const var9 = <div>Text9</div>;
+
+const var10 = <div>
+    <div>Text</div>
+    <div>Text</div>
+    <div>Text</div>
+</div>;`
+);
\ No newline at end of file