Reintroduce WriteAttribute methods on RazorView type

samples/MvcSample/Views/Home/MyView.cshtml

@@ -3,6 +3,7 @@
 @{
     Layout = "/Views/Shared/_Layout.cshtml";
     ViewBag.Title = "Home Page";
+    string nullValue = null;
 }
 
 <div class="jumbotron">
@@ -11,7 +12,8 @@
     <p><a href="http://asp.net" class="btn btn-primary btn-large">Learn more &raquo;</a></p>
 </div>
 <div class="row">
-    <h3>Hello @Model.Name!</h3>
+    <h3 title="@Model.Name" class="@nullValue">Hello @Model.Name!</h3>
+    
     <div class="col-md-4">
         <h2>Getting started</h2>
         <p>

src/Microsoft.AspNet.Mvc.Razor/AttributeValue.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+
+namespace Microsoft.AspNet.Mvc.Razor
+{
+    public class AttributeValue
+    {
+        public AttributeValue(PositionTagged<string> prefix, PositionTagged<object> value, bool literal)
+        {
+            Prefix = prefix;
+            Value = value;
+            Literal = literal;
+        }
+
+        public PositionTagged<string> Prefix { get; private set; }
+
+        public PositionTagged<object> Value { get; private set; }
+
+        public bool Literal { get; private set; }
+
+        [SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "We are using tuples here to avoid dependencies from Razor to WebPages")]
+        public static AttributeValue FromTuple(Tuple<Tuple<string, int>, Tuple<object, int>, bool> value)
+        {
+            return new AttributeValue(value.Item1, value.Item2, value.Item3);
+        }
+
+        [SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "We are using tuples here to avoid dependencies from Razor to WebPages")]
+        public static AttributeValue FromTuple(Tuple<Tuple<string, int>, Tuple<string, int>, bool> value)
+        {
+            return new AttributeValue(value.Item1, new PositionTagged<object>(value.Item2.Item1, value.Item2.Item2), value.Item3);
+        }
+
+        [SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "We are using tuples here to avoid dependencies from Razor to WebPages")]
+        public static implicit operator AttributeValue(Tuple<Tuple<string, int>, Tuple<object, int>, bool> value)
+        {
+            return FromTuple(value);
+        }
+
+        [SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "We are using tuples here to avoid dependencies from Razor to WebPages")]
+        public static implicit operator AttributeValue(Tuple<Tuple<string, int>, Tuple<string, int>, bool> value)
+        {
+            return FromTuple(value);
+        }
+    }
+}

src/Microsoft.AspNet.Mvc.Razor/PositionTagged.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Diagnostics;
+
+namespace Microsoft.AspNet.Mvc.Razor
+{
+    [DebuggerDisplay("({Position})\"{Value}\"")]
+    public class PositionTagged<T>
+    {
+        public PositionTagged(T value, int offset)
+        {
+            Position = offset;
+            Value = value;
+        }
+
+        public int Position { get; private set; }
+
+        public T Value { get; private set; }
+
+        public override string ToString()
+        {
+            return Value.ToString();
+        }
+
+        public static implicit operator T(PositionTagged<T> value)
+        {
+            return value.Value;
+        }
+
+        public static implicit operator PositionTagged<T>(Tuple<T, int> value)
+        {
+            return new PositionTagged<T>(value.Item1, value.Item2);
+        }
+    }
+}

src/Microsoft.AspNet.Mvc.Razor/RazorView.cs

@@ -92,6 +92,104 @@ namespace Microsoft.AspNet.Mvc.Razor
             }
         }
 
+        public virtual void WriteAttribute(string name,
+                                           PositionTagged<string> prefix,
+                                           PositionTagged<string> suffix,
+                                           params AttributeValue[] values)
+        {
+            WriteAttributeTo(Output, name, prefix, suffix, values);
+        }
+
+        public virtual void WriteAttributeTo(TextWriter writer,
+                                             string name,
+                                             PositionTagged<string> prefix,
+                                             PositionTagged<string> suffix,
+                                             params AttributeValue[] values)
+        {
+            bool first = true;
+            bool wroteSomething = false;
+            if (values.Length == 0)
+            {
+                // Explicitly empty attribute, so write the prefix and suffix
+                WritePositionTaggedLiteral(writer, prefix);
+                WritePositionTaggedLiteral(writer, suffix);
+            }
+            else
+            {
+                for (int i = 0; i < values.Length; i++)
+                {
+                    AttributeValue attrVal = values[i];
+                    PositionTagged<object> val = attrVal.Value;
+                    PositionTagged<string> next = i == values.Length - 1 ?
+                        suffix : // End of the list, grab the suffix
+                        values[i + 1].Prefix; // Still in the list, grab the next prefix
+
+                    if (val.Value == null)
+                    {
+                        // Nothing to write
+                        continue;
+                    }
+
+                    // The special cases here are that the value we're writing might already be a string, or that the 
+                    // value might be a bool. If the value is the bool 'true' we want to write the attribute name instead
+                    // of the string 'true'. If the value is the bool 'false' we don't want to write anything.
+                    //
+                    // Otherwise the value is another object (perhaps an IHtmlString), and we'll ask it to format itself.
+                    string stringValue;
+                    bool? boolValue = val.Value as bool?;
+                    if (boolValue == true)
+                    {
+                        stringValue = name;
+                    }
+                    else if (boolValue == false)
+                    {
+                        continue;
+                    }
+                    else
+                    {
+                        stringValue = val.Value as string;
+                    }
+
+                    if (first)
+                    {
+                        WritePositionTaggedLiteral(writer, prefix);
+                        first = false;
+                    }
+                    else
+                    {
+                        WritePositionTaggedLiteral(writer, attrVal.Prefix);
+                    }
+
+                    // Calculate length of the source span by the position of the next value (or suffix)
+                    int sourceLength = next.Position - attrVal.Value.Position;
+
+                    if (attrVal.Literal)
+                    {
+                        WriteLiteralTo(writer, stringValue ?? val.Value);
+                    }
+                    else
+                    {
+                        WriteTo(writer, stringValue ?? val.Value); // Write value
+                    }
+                    wroteSomething = true;
+                }
+                if (wroteSomething)
+                {
+                    WritePositionTaggedLiteral(writer, suffix);
+                }
+            }
+        }
+
+        private void WritePositionTaggedLiteral(TextWriter writer, string value, int position)
+        {
+            WriteLiteralTo(writer, value);
+        }
+
+        private void WritePositionTaggedLiteral(TextWriter writer, PositionTagged<string> value)
+        {
+            WritePositionTaggedLiteral(writer, value.Value, value.Position);
+        }
+
         protected virtual HtmlString RenderBody()
         {
             if (BodyContent == null)