How to mix HTML and C# Code in MVC3 with Razor?

Let’s start with improving your code.

• Improvement step 1:

  @foreach(var myObj in Model.Select((model, index) => new { model, index }))
  {
      <div class="class@(myObj.index % 2 == 0 ? "1" : "2")">
          @Html.Partial("_Foo", myObj.model)
      </div>
  }
  

• Improvement Step 2 (using a custom HTML helper for the class):

  @foreach(var myObj in Model.Select((model, index) => new { model, index }))
  {
      <div class="@Html.MyClass(myObj.index)">
          @Html.Partial("_Foo", myObj.model)
      </div>
  }
  

  where MyClass is defined like this:

  public static string MyClass(this HtmlHelper html, int index)
  {
      return (index % 2 == 0) ? "class1" : "class2";
  }
  

• Improvement step 3 which is the state of the art (using Templated Razor Delegates):

  @Model.List(
      @<div class="@item.MyClass">
          @Html.Partial("_Foo", @item.Model)
      </div>
  )
  

  where the List extension method looks like this:

  public class ModelHolder<T>
  {
      public T Model { get; set; }
      public string MyClass { get; set; }
  }
  
  public static class RazorExtensions
  {
      public static HelperResult List<T>(
          this IEnumerable<T> items,
          Func<ModelHolder<T>, HelperResult> template
      )
      {
          return new HelperResult(writer =>
          {
              foreach (var item in items.Select((model, index) => new { model, index }))
              {
                  var myClass = item.index % 2 == 0 ? "class1" : "class2";
                  template(new ModelHolder<T> { Model = item.model, MyClass = myClass }).WriteTo(writer);
              }
          });
      }
  }
  

I vote for improvement number 3 which is far better and more concise than the original foreach loop.