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

问题:

I am trying to display a list of items that should toggle a class for styling purposes. The idea is to create a foreach loop that will cycle through all the myObj in the Model.

I tried the following code which does not work (because I'm doing it wrong)

@{ int i = 2;
   foreach(var myObj in Model)
   {
        if (i % 2 == 0)
        {
            <div class="class1">
        }
        else
        {
            <div class="class2">
        }
        Html.Partial(...);
        </div>
         i += 1;
   }     
}

What is the proper way to accomplish this?

Update
I also tried the following code that, although compiles, does not render any HTML code within (and I'm sure there are objects in Model).

@{ int i = 2;
   foreach(var myObj in Model)
   {
        if (i % 2 == 0)
        {
            @:<div class="class1">
        }
        else
        {
            @:<div class="class2">
        }
        Html.Partial(...);
        @:</div>

        i += 1;
   }

}

This is the partial class being called

<div class="class">
    <div class="class2">
        @if (string.IsNullOrEmpty(var))
        {
            @var2
        }
        else
        {
            @var
        }
    </div>
    <div class="class3">
        @var3
    </div>
</div>
<div class="class4">
    <p>var4</p>
    <ul class="class5">
        <li>element1</li>
        <li>element2</li>
    </ul>
</div>

I'm sorry I can't post the actual names and variables.

回答1:

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.

回答2:

You need to prefix the lines with non-well-formed tags with @: to prevent Razor from trying to parse the tags.
Details.

回答3:

You may be sure there are objects in some model - but not your model : ) the following sample code derived directly from yours works just fine:

@{ int i = 2;
   string[] list = new string[] {"a","b","c","d"};
   foreach(var myObj in list)
   {
        if (i % 2 == 0){
            @:<div class="class1">
        }
        else
        {
            @:<div class="class2">
        }
        //Html.Partial(...);
        @:</div>
         i += 1;
   }     
}

回答4:

You need to write @Html.Partial(...) to render the result to the page.

Calling Html.Partial returns a HelperResult with the partial view, but doesn't actually render it.