如何使用Razor视图引擎在JavaScript中正确混合C＃代码。 我希望根据ViewBag中的值包含或省略Javascript

Question

So I only want this JavaScript to be included in the response to the browser if ViewBag.L1Cat does not equal null. At the moment I am getting the error: cannot perform run time binding on a null reference. And the debugger does not want to stop inside the if statement for some reason. ViewBag was populated with respective keys\\value pairs in the action method that returns the view.

 <script type="text/javascript">
 @{
    if(ViewBag.L1Cat != null)
    {
       <text>              
          var FirstLevel = 
                    $('#MenuContainer')
                       .find('.FirstLevel')
                       .attr('@(ViewBag.RootCat.ToString());');
       </text>        
     }
   }    
 </script>

Answer 1

Is it absolutely necessary to omit the code?

You might find it cleaner to take this approach:

<script type="text/javascript">
var doStuff = @(ViewBag.L1Cat != null ? "true" : "false");
if (doStuff)
{
var FirstLevel = $('#MenuContainer').find('.FirstLevel').attr('@(ViewBag.RootCat.ToString())');
}
</script>

Alternatively

<script type="text/javascript">
@if(ViewBag.L1Cat != null)
{
 <text>              
  var FirstLevel = $('#MenuContainer').find('.FirstLevel').attr('@(ViewBag.RootCat.ToString())');
 </text>        
}
</script>