title: Failed to @Html.DropDownList()
body: <p>I did check all issues about that but I couldn't figure out how to solve it. I need to your help guys.</p>
  
  <p>Here is my code about dropdownlist. When I post the page I got the error message which I mentioned above. ERROR:</p>
  
  <blockquote>
    <p>An exception of type 'System.NullReferenceException' occurred in App_Web_ikconokc.dll but was not handled in user code
    Additional information: Object reference not set to an instance of an object.</p>
  </blockquote>
  
  <p>I want to use 2 models in 1 view. All works well except @Html.DropDownList. In View:</p>
  
  <pre><code>@model Tuple&lt;Models.Framework.Drink, Models.Framework.Drinks_Category&gt;
  
  
      &lt;div class="form-group"&gt;
          @Html.LabelFor(tuple =&gt; tuple.Item2.Id_category, "Id_category", htmlAttributes: new { @class = "control-label col-md-2" })
          &lt;div class="col-md-10"&gt;
              @Html.DropDownList("Id_category", new SelectList( Model.Item2.Id_category.ToList()), new { @class = "control-label col-md-2" })
  
              @Html.ValidationMessageFor(tuple =&gt; tuple.Item1.Id_category, "", new { @class = "text-danger" })
          &lt;/div&gt;
      &lt;/div&gt;
  </code></pre>
  
  <p>I tried the following code but still get error:</p>
  
  <pre><code>@Html.DropDownList("Id_category", new SelectList( Model.Item2.Id_category, "Value", "Text", Model.Item2), new { @class = "control-label col-md-2" })
  </code></pre>
  
  <p>Table "Drink" is associated with table "Drinks_Category" with key Id_category. I want to use 2 models in 1 view. Please help me!</p>