How does Telerik MVC extensions render template columns - asp.net-mvc

Question

I've just been looking at the source code for the Telerik MVC extensions and can't for the life of me work out how the template columns work. I can get them to work just fine, but I'm trying to understand what is happening under the hood, as I think they are really useful. I've stepped through the source code but I'm still a bit confused. Here's an example from the source code's example project.
Html.Telerik().Grid(Model)
.Name("Grid")
.Columns(columns =>
{
columns.Template(c => {
%><img
alt="<%= c.CustomerID %>"
src="<%= Url.Content("~/Content/Grid/Customers/" + c.CustomerID + ".jpg") %>"
/><%
}).Title("Picture");
columns.Bound(c => c.ContactName).Title("Name");
columns.Bound(c => c.Phone);
})
.Sortable()
.Scrollable(scrolling => scrolling.Height(250))
.Pageable()
.Render();
The columns => {} delegate is of type Action<GridColumnFactory<T>>
where Model is IEnumerable<T> and the c=>{} delegate is of type Action<TModel> . That much I understand, the Template method on the GridColumnFactory is given an action as a parameter.
How is this action used to render the required HTML?
Thanks !!!

Answer 1

The magic here is that Telerik uses the fact that any content (HTML, JavaScript, etc) inside ASP.NET Web Pages is in fact translated into a Response.Write-like call by the page compiler.
For example;
<% Action action = () => { %><h1>Title</h1><% }; %>
Will be translated to something like this C# code:
Action action = () => { Response.Write("<h1>Title</h1>"); };
Once you understand this, it's no different than other methods: for each cell, Telerik simply call the Action you wrote without realizing it, which contains one or more Write calls generated by the compiler.