Why can't I use my extension method in a delegate in the Razor WebGrid

Question

I'm using the MVC 3 introduced WebGrid, but can't can't apply my own extension methods when passing a delegate for the format param.

Using:

Grid.Column("MyProperty", "MyProperty", 
format: @<span class="something">@item.MyProperty.MyExtensionMethodForString()</span>)

I got

ERROR: 'string' does not contain a definition for 'MyExtensionMethodForString'

I've tried casting, not to avail

Grid.Column("MyProperty", "MyProperty", 
format: @<span class="something">@((string)(item.MyProperty).MyExtensionMethodForString())</span>)

If I use an standard method, it works:

Grid.Column("MyProperty", "MyProperty", 
format: @<span class="something">@(Utils.MyExtensionMethodForString(item.MyProperty))</span>)

I've also tried to put the extension in the same namespace, with no results.

How can I use my beloved extensions?

Edit: The namespace per se it's not the problem, the namespace where the extension is available for all the views and classes, and I can use it in the same view without problem. The problem is when using it in the delegate.

Answer 1

This is not a limitation of the WebGrid or Razor. It's a limitation of the C# dynamic type. You cannot use extension methods on dynamic. The format helper takes a Func<dynamic, object> as an argument, so the item parameter is a dynamic type.

I wrote about this exact issue a couple of years ago.