diff --git a/src/System.Collections.Concurrent/tests/System.Collections.Concurrent.Tests.csproj b/src/System.Collections.Concurrent/tests/System.Collections.Concurrent.Tests.csproj
index 88f05125e65c..5d3c9a88962d 100644
--- a/src/System.Collections.Concurrent/tests/System.Collections.Concurrent.Tests.csproj
+++ b/src/System.Collections.Concurrent/tests/System.Collections.Concurrent.Tests.csproj
@@ -10,7 +10,7 @@
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'netstandard-Debug|AnyCPU'" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'netstandard-Release|AnyCPU'" />
   <ItemGroup>
-    <Compile Include="$(CommonTestPath)\System\Collections\DictionaryExtensions.cs">
+    <Compile Include="$(CommonTestPath)\System\Collections\DictionaryExtensions.cs" Condition="'$(TargetGroup)'!='netcoreapp'">
       <Link>Common\System\Collections\DictionaryExtensions.cs</Link>
     </Compile>
     <!-- Common Collections tests -->
diff --git a/src/System.Collections.Immutable/tests/System.Collections.Immutable.Tests.csproj b/src/System.Collections.Immutable/tests/System.Collections.Immutable.Tests.csproj
index 01a3daf0d60d..0562168caad7 100644
--- a/src/System.Collections.Immutable/tests/System.Collections.Immutable.Tests.csproj
+++ b/src/System.Collections.Immutable/tests/System.Collections.Immutable.Tests.csproj
@@ -14,7 +14,7 @@
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'uap-Debug|AnyCPU'" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'uap-Release|AnyCPU'" />
   <ItemGroup>
-    <Compile Include="$(CommonTestPath)\System\Collections\DictionaryExtensions.cs">
+    <Compile Include="$(CommonTestPath)\System\Collections\DictionaryExtensions.cs" Condition="'$(TargetGroup)'!='netcoreapp' And '$(TargetGroup)'!='uap'">
       <Link>Common\System\Collections\DictionaryExtensions.cs</Link>
     </Compile>
     <Compile Include="BadHasher.cs" />
diff --git a/src/System.Collections/ref/System.Collections.cs b/src/System.Collections/ref/System.Collections.cs
index 81db6619e614..feeb5b8632dc 100644
--- a/src/System.Collections/ref/System.Collections.cs
+++ b/src/System.Collections/ref/System.Collections.cs
@@ -49,6 +49,9 @@ public static class CollectionExtensions
 
         public static TValue GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, TKey key) { throw null; }
         public static TValue GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, TKey key, TValue defaultValue) { throw null; }
+
+        public static bool TryAdd<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, TValue value) { throw null; }
+        public static bool Remove<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, out TValue value) { throw null; }
     }
     public abstract partial class Comparer<T> : System.Collections.Generic.IComparer<T>, System.Collections.IComparer
     {
diff --git a/src/System.Collections/src/System/Collections/Generic/CollectionExtensions.cs b/src/System.Collections/src/System/Collections/Generic/CollectionExtensions.cs
index e3a5ef2e95a8..4a4078d565c0 100644
--- a/src/System.Collections/src/System/Collections/Generic/CollectionExtensions.cs
+++ b/src/System.Collections/src/System/Collections/Generic/CollectionExtensions.cs
@@ -37,5 +37,38 @@ public static TValue GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TK
             TValue value;            
             return dictionary.TryGetValue(key, out value) ? value : defaultValue;
         }
+
+        public static bool TryAdd<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, TValue value)
+        {
+            if (dictionary == null)
+            {
+                throw new ArgumentNullException(nameof(dictionary));
+            }
+
+            if (!dictionary.ContainsKey(key))
+            {
+                dictionary.Add(key, value);
+                return true;
+            }
+
+            return false;
+        }
+
+        public static bool Remove<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, out TValue value)
+        {
+            if (dictionary == null)
+            {
+                throw new ArgumentNullException(nameof(dictionary));
+            }
+
+            if (dictionary.TryGetValue(key, out value))
+            {
+                dictionary.Remove(key);
+                return true;
+            }
+
+            value = default(TValue);
+            return false;
+        }
     }
 }
diff --git a/src/System.Collections/tests/Generic/CollectionExtensionsTests.cs b/src/System.Collections/tests/Generic/CollectionExtensionsTests.cs
index 74501974d91a..13d5f7aa56e0 100644
--- a/src/System.Collections/tests/Generic/CollectionExtensionsTests.cs
+++ b/src/System.Collections/tests/Generic/CollectionExtensionsTests.cs
@@ -72,5 +72,70 @@ public void GetValueOrDefault_NullIReadOnlyDictionary_ThrowsArgumentNullExceptio
             Assert.Throws<ArgumentNullException>("dictionary", () => dictionary.GetValueOrDefault("key"));
             Assert.Throws<ArgumentNullException>("dictionary", () => dictionary.GetValueOrDefault("key", "value"));
         }
+
+        [Fact]
+        public void TryAdd_NullIDictionary_ThrowsArgumentNullException()
+        {
+            IDictionary<string, string> dictionary = null;
+            Assert.Throws<ArgumentNullException>("dictionary", () => dictionary.TryAdd("key", "value"));
+        }
+
+        [Fact]
+        public void TryAdd_NullKeyIDictionary_ThrowsArgumentNullException()
+        {
+            IDictionary<string, string> dictionary = new SortedDictionary<string, string>();
+            Assert.Throws<ArgumentNullException>("key", () => dictionary.TryAdd(null, "value"));
+        }
+
+        [Fact]
+        public void TryAdd_KeyDoesntExistInIDictionary_ReturnsTrue()
+        {
+            IDictionary<string, string> dictionary = new SortedDictionary<string, string>();
+            Assert.True(dictionary.TryAdd("key", "value"));
+            Assert.Equal("value", dictionary["key"]);
+        }
+
+        [Fact]
+        public void TryAdd_KeyExistsInIDictionary_ReturnsFalse()
+        {
+            IDictionary<string, string> dictionary = new SortedDictionary<string, string>() { ["key"] = "value" };
+            Assert.False(dictionary.TryAdd("key", "value2"));
+            Assert.Equal("value", dictionary["key"]);
+        }
+
+        [Fact]
+        public void Remove_NullIDictionary_ThrowsArgumentNullException()
+        {
+            IDictionary<string, string> dictionary = null;
+            string value = null;
+            Assert.Throws<ArgumentNullException>("dictionary", () => dictionary.Remove("key", out value));
+            Assert.Null(value);
+        }
+
+        [Fact]
+        public void Remove_NullKeyIDictionary_ThrowsArgumentNullException()
+        {
+            IDictionary<string, string> dictionary = new SortedDictionary<string, string>();
+            string value = null;
+            Assert.Throws<ArgumentNullException>("key", () => dictionary.Remove(null, out value));
+            Assert.Null(value);
+        }
+
+        [Fact]
+        public void Remove_KeyExistsInIDictionary_ReturnsTrue()
+        {
+            IDictionary<string, string> dictionary = new SortedDictionary<string, string>() { ["key"] = "value" };
+            Assert.True(dictionary.Remove("key", out var value));
+            Assert.Equal("value", value);
+            Assert.Throws<KeyNotFoundException>(() => dictionary["key"]);
+        }
+
+        [Fact]
+        public void Remove_KeyDoesntExistInIDictionary_ReturnsFalse()
+        {
+            IDictionary<string, string> dictionary = new SortedDictionary<string, string>();
+            Assert.False(dictionary.Remove("key", out var value));
+            Assert.Equal(default(string), value);
+        }
     }
 }
diff --git a/src/System.Collections/tests/System.Collections.Tests.csproj b/src/System.Collections/tests/System.Collections.Tests.csproj
index d820abc79a0d..1a3a94b83614 100644
--- a/src/System.Collections/tests/System.Collections.Tests.csproj
+++ b/src/System.Collections/tests/System.Collections.Tests.csproj
@@ -71,7 +71,7 @@
     <Compile Include="$(CommonTestPath)\System\ObjectCloner.cs">
       <Link>Common\System\ObjectCloner.cs</Link>
     </Compile>
-    <Compile Include="$(CommonTestPath)\System\Collections\DictionaryExtensions.cs">
+    <Compile Include="$(CommonTestPath)\System\Collections\DictionaryExtensions.cs" Condition="'$(TargetGroup)'!='netcoreapp'">
       <Link>Common\System\Collections\DictionaryExtensions.cs</Link>
     </Compile>
     <!-- Generic tests -->
@@ -161,4 +161,4 @@
     </Compile>
   </ItemGroup>
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
-</Project>
\ No newline at end of file
+</Project>