Merge branch 'release/2.2'

Author: dougbu

src/Microsoft.AspNetCore.Razor/TagHelpers/DefaultTagHelperContent.cs

@@ -221,8 +221,7 @@ private void WriteToCore(object entry, TextWriter writer, HtmlEncoder encoder)
                 return;
             }
 
-            var stringValue = entry as string;
-            if (stringValue != null)
+            if (entry is string stringValue)
             {
                 encoder.Encode(writer, stringValue);
             }
@@ -239,13 +238,11 @@ private void CopyToCore(object entry, IHtmlContentBuilder destination)
                 return;
             }
 
-            string entryAsString;
-            IHtmlContentContainer entryAsContainer;
-            if ((entryAsString = entry as string) != null)
+            if (entry is string entryAsString)
             {
                 destination.Append(entryAsString);
             }
-            else if ((entryAsContainer = entry as IHtmlContentContainer) != null)
+            else if (entry is IHtmlContentContainer entryAsContainer)
             {
                 entryAsContainer.CopyTo(destination);
             }
@@ -262,13 +259,11 @@ private void MoveToCore(object entry, IHtmlContentBuilder destination)
                 return;
             }
 
-            string entryAsString;
-            IHtmlContentContainer entryAsContainer;
-            if ((entryAsString = entry as string) != null)
+            if (entry is string entryAsString)
             {
                 destination.Append(entryAsString);
             }
-            else if ((entryAsContainer = entry as IHtmlContentContainer) != null)
+            else if (entry is IHtmlContentContainer entryAsContainer)
             {
                 entryAsContainer.MoveTo(destination);
             }
@@ -282,29 +277,19 @@ private bool IsEmptyOrWhiteSpaceCore(object entry, EmptyOrWhiteSpaceWriter write
         {
             if (entry == null)
             {
-                return false;
+                return true;
             }
 
-            var stringValue = entry as string;
-            if (stringValue != null)
+            if (entry is string stringValue)
             {
                 // Do not encode the string because encoded value remains whitespace from user's POV.
-                if (!string.IsNullOrWhiteSpace(stringValue))
-                {
-                    return false;
-                }
-            }
-            else
-            {
-                // Use NullHtmlEncoder to avoid treating encoded whitespace as non-whitespace e.g. "\t" as "	".
-                ((IHtmlContent)entry).WriteTo(writer, NullHtmlEncoder.Default);
-                if (!writer.IsEmptyOrWhiteSpace)
-                {
-                    return false;
-                }
+                return string.IsNullOrWhiteSpace(stringValue);
             }
 
-            return true;
+            // Use NullHtmlEncoder to avoid treating encoded whitespace as non-whitespace e.g. "\t" as "	".
+            ((IHtmlContent)entry).WriteTo(writer, NullHtmlEncoder.Default);
+
+            return writer.IsEmptyOrWhiteSpace;
         }
 
         private TagHelperContent AppendCore(object entry)
@@ -329,7 +314,7 @@ private string DebuggerToString()
         {
             return GetContent();
         }
-        
+
         // Overrides Write(string) to find if the content written is empty/whitespace.
         private class EmptyOrWhiteSpaceWriter : TextWriter
         {
@@ -360,4 +345,4 @@ public override void Write(string value)
             }
         }
     }
-}
+}

test/Microsoft.AspNetCore.Razor.Test/TagHelpers/DefaultTagHelperContentTest.cs

@@ -363,6 +363,7 @@ public static TheoryData<string> EmptyOrWhiteSpaceData
             {
                 return new TheoryData<string>
                 {
+                    null,
                     string.Empty,
                     " ",
                     "\n",
@@ -838,4 +839,4 @@ public void WriteTo(TextWriter writer, HtmlEncoder encoder)
             }
         }
     }
-}
+}