[Fixes #804] Fixed unsafe cast in CSharpCodeVisitor

src/Microsoft.AspNetCore.Razor/CodeGenerators/Visitors/CSharpCodeVisitor.cs

@@ -399,29 +399,38 @@ protected override void Visit(SectionChunk chunk)
 
         public void RenderDesignTimeExpressionBlockChunk(ExpressionBlockChunk chunk)
         {
-            var firstChild = (ExpressionChunk)chunk.Children.FirstOrDefault();
-
+            var firstChild = chunk.Children.FirstOrDefault();
             if (firstChild != null)
             {
                 var currentIndent = Writer.CurrentIndent;
-                var designTimeAssignment = "__o = ";
                 Writer.ResetIndent();
 
                 var documentLocation = firstChild.Association.Start;
+
                 // This is only here to enable accurate formatting by the C# editor.
                 Writer.WriteLineNumberDirective(documentLocation, Context.SourceFile);
 
-                // We build the padding with an offset of the design time assignment statement.
-                Writer.Write(_paddingBuilder.BuildExpressionPadding((Span)firstChild.Association, designTimeAssignment.Length))
-                      .Write(designTimeAssignment);
+                var designTimeAssignment = "__o = ";
+                var firstChildExpressionChunk = firstChild as ExpressionChunk;
+                if (firstChildExpressionChunk != null)
+                {
+                    // We build the padding with an offset of the design time assignment statement.
+                    Writer.Write(_paddingBuilder.BuildExpressionPadding((Span)firstChildExpressionChunk.Association, designTimeAssignment.Length))
+                          .Write(designTimeAssignment);
 
-                // We map the first line of code but do not write the line pragmas associated with it.
-                CreateRawCodeMapping(firstChild.Code, documentLocation);
+                    // We map the first line of code but do not write the line pragmas associated with it.
+                    CreateRawCodeMapping(firstChildExpressionChunk.Code, documentLocation);
 
-                // Render all but the first child.
-                // The reason why we render the other children differently is because when formatting the C# code
-                // the formatter expects the start line to have the assignment statement on it.
-                Accept(chunk.Children.Skip(1).ToList());
+                    // Render all but the first child.
+                    // The reason why we render the other children differently is because when formatting the C# code
+                    // the formatter expects the start line to have the assignment statement on it.
+                    Accept(chunk.Children.Skip(1).ToList());
+                }
+                else
+                {
+                    // First child is not an expression block
+                    Accept(chunk.Children.ToList());
+                }
 
                 Writer.WriteLine(";")
                       .WriteLine()

src/Microsoft.AspNetCore.Razor/Parser/CSharpCodeParser.cs

@@ -645,7 +645,11 @@ protected override void HandleEmbeddedTransition()
         {
             if (Language.IsTransition(CurrentSymbol))
             {
+                //Accept(CurrentSymbol);
+                //NextToken();
+                //Output(SpanKind.Transition);
                 PutCurrentBack();
+                Output(SpanKind.Code);
                 Template();
             }
             else if (Language.IsCommentStart(CurrentSymbol))

test/Microsoft.AspNetCore.Razor.Test/CodeGenerators/CSharpRazorCodeGeneratorTest.cs

@@ -404,6 +404,11 @@ public void CSharpChunkGeneratorCorrectlyGeneratesDesignTimePragmasMarkupAndExpr
             });
         }
 
+        [Fact]
+        public void CSharpChunkGeneratorCorrectlyGeneratesDesignTimePragmasForExplicitExpressionContainingMarkup()
+        {
+            RunTest("ExplicitExpressionWithMarkup", designTimeMode: true, expectedDesignTimePragmas: new List<LineMapping>());
+        }
 
         [Fact]
         public void CSharpChunkGeneratorCorrectlyGeneratesDesignTimePragmasForImplicitExpressionStartedAtEOF()

test/Microsoft.AspNetCore.Razor.Test/TestFiles/CodeGenerator/Output/ExplicitExpressionWithMarkup.cs

@@ -0,0 +1,33 @@
+namespace TestOutput
+{
+    using System;
+    using System.Threading.Tasks;
+
+    public class ExplicitExpressionWithMarkup
+    {
+        private static object @__o;
+        private void @__RazorDesignTimeHelpers__()
+        {
+            #pragma warning disable 219
+            #pragma warning restore 219
+        }
+        #line hidden
+        public ExplicitExpressionWithMarkup()
+        {
+        }
+
+        #pragma warning disable 1998
+        public override async Task ExecuteAsync()
+        {
+#line 1 "ExplicitExpressionWithMarkup.cshtml"
+item => new Template(async(__razor_template_writer) => {
+}
+)
+;
+
+#line default
+#line hidden
+        }
+        #pragma warning restore 1998
+    }
+}

test/Microsoft.AspNetCore.Razor.Test/TestFiles/CodeGenerator/Source/ExplicitExpressionWithMarkup.cshtml

@@ -0,0 +1 @@
+<div>@(@</div>