[NoMerge] React to StringValues

src/Microsoft.AspNetCore.Http.Abstractions/Extensions/HeaderDictionaryExtensions.cs

@@ -39,7 +39,7 @@ public static void AppendCommaSeparatedValues(this IHeaderDictionary headers, st
         /// <returns>the associated values from the collection separated into individual values, or StringValues.Empty if the key is not present.</returns>
         public static string[] GetCommaSeparatedValues(this IHeaderDictionary headers, string key)
         {
-            return ParsingHelpers.GetHeaderSplit(headers, key).ToArray();
+            return ParsingHelpers.GetHeaderSplit(headers, key);
         }
 
         /// <summary>

src/Microsoft.AspNetCore.Http.Abstractions/Internal/ParsingHelpers.cs

@@ -153,7 +153,7 @@ public static void AppendHeaderUnmodified(IHeaderDictionary headers, string key,
                 throw new ArgumentNullException(nameof(key));
             }
 
-            if (values.Count == 0)
+            if (values.IsNull)
             {
                 return;
             }

src/Microsoft.AspNetCore.Http/HeaderDictionary.cs

@@ -74,7 +74,7 @@ public StringValues this[string key]
                 }
                 ThrowIfReadOnly();
 
-                if (StringValues.IsNullOrEmpty(value))
+                if (value.ToString().Length == 0)
                 {
                     Store?.Remove(key);
                 }
@@ -177,8 +177,11 @@ public void Add(KeyValuePair<string, StringValues> item)
                 throw new ArgumentNullException("The key is null");
             }
             ThrowIfReadOnly();
-            EnsureStore(1);
-            Store.Add(item.Key, item.Value);
+            if (item.Value.ToString().Length > 0)
+            {
+                EnsureStore(1);
+                Store.Add(item.Key, item.Value);
+            }
         }
 
         /// <summary>
@@ -193,8 +196,11 @@ public void Add(string key, StringValues value)
                 throw new ArgumentNullException(nameof(key));
             }
             ThrowIfReadOnly();
-            EnsureStore(1);
-            Store.Add(key, value);
+            if (value.ToString().Length > 0)
+            {
+                EnsureStore(1);
+                Store.Add(key, value);
+            }
         }
 
         /// <summary>

src/Microsoft.AspNetCore.WebUtilities/KeyValueAccumulator.cs

@@ -22,7 +22,7 @@ public void Append(string key, string value)
             StringValues values;
             if (_accumulator.TryGetValue(key, out values))
             {
-                if (values.Count == 0)
+                if (values.IsNull)
                 {
                     // Marker entry for this key to indicate entry already in expanding list dictionary
                     _expandingAccumulator[key].Add(value);