title: IFormFile always null (ASP.NET Core with MVC/Razor)
body: <p>I have an ASP.NET Core MVC app attempting to upload an IFormFile. However, the IFormFile is always null. None of the other solutions I've found have solved this issue. What am I doing wrong?</p>
  
  <p>Model</p>
  
  <pre><code>public class EmailForm
  {
      [Display(Name = "Add a picture")]
      [DataType(DataType.Upload)]
      [FileExtensions(Extensions = "jpg,png,gif,jpeg,bmp,svg")]
      public IFormFile SubmitterPicture { get; set; }
  }
  </code></pre>
  
  <p>Controller</p>
  
  <pre><code>public async Task&lt;ActionResult&gt; Contribute([Bind("SubmitterPicture")] EmailForm model)
  {
      if (ModelState.IsValid)
      {
          //Do some stuff
      }
  }
  </code></pre>
  
  <p>View</p>
  
  <pre><code>        &lt;form method="post" asp-action="Contribute" asp-antiforgery="true" enctype="multipart/form-data" &gt;
              &lt;div class="form-group" &gt;
                  &lt;div class="col-md-2"&gt;@Html.LabelFor(m =&gt; m.SubmitterPicture)&lt;/div&gt;
                  &lt;div class="col-md-4"&gt;
                      &lt;input type="file" name="SubmitterPicture" id="SubmitterPicture" /&gt;
      &lt;/div&gt;
              &lt;div class="form-group"&gt;
                  &lt;div class="col-md-offset-2 col-md-10"&gt;
                      &lt;input type="submit" class="btn btn-default" value="Contribute" /&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
  </code></pre>