Disable async await warnings in empty Execute method.

Also removed a confusing CSharpCodeWriting method.

#28

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeBuilder/CSharp/CSharpCodeBuilder.cs

@@ -57,9 +57,13 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
                     // Add space inbetween constructor and method body
                     writer.WriteLine();
 
-                    using (writer.BuildMethodDeclaration("public override async", "Task", Host.GeneratedClassContext.ExecuteMethodName))
+                    // 1998 is to not warn about empty async methods.
+                    using (writer.BuildDisableWarningScope(1998))
                     {
-                        new CSharpCodeVisitor(writer, Context).Accept(Tree.Chunks);
+                        using (writer.BuildMethodDeclaration("public override async", "Task", Host.GeneratedClassContext.ExecuteMethodName))
+                        {
+                            new CSharpCodeVisitor(writer, Context).Accept(Tree.Chunks);
+                        }
                     }
                 }
             }

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeBuilder/CSharp/CSharpCodeWriter.cs

@@ -226,11 +226,6 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
             return WriteStartMethodInvocation(methodName).Write(string.Join(", ", parameters)).WriteEndMethodInvocation(endLine);
         }
 
-        public CSharpDisableWarningScope BuildDisableWarningScope()
-        {
-            return new CSharpDisableWarningScope(this, 219);
-        }
-
         public CSharpDisableWarningScope BuildDisableWarningScope(int warning)
         {
             return new CSharpDisableWarningScope(this, warning);

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeBuilder/CSharp/Visitors/CSharpDesignTimeHelpersVisitor.cs

@@ -17,7 +17,7 @@ namespace Microsoft.AspNet.Razor.Generator.Compiler.CSharp
             {
                 using (Writer.BuildMethodDeclaration("private", "void", "@" + DesignTimeHelperMethodName))
                 {
-                    using (Writer.BuildDisableWarningScope())
+                    using (Writer.BuildDisableWarningScope(219))
                     {
                         Accept(tree.Chunks);
                     }