title: File upload control to upload PDF only
body: <p>I got a file control like</p>
  
  <pre><code> &lt;div class="form-group"&gt;
          @Html.LabelFor(m =&gt; m.File, new { @class = "col-md-2 control-label" })
          &lt;div class="col-md-10"&gt;
              @Html.TextBoxFor(m =&gt; m.File, new { type = "file" })
  
          &lt;/div&gt;
  </code></pre>
  
  <p>I want it to allow only PDF format files, so in my model, its like</p>
  
  <pre><code> [Display(Name = "Terms of Business")]
          [Required, FileExtensions(Extensions=".pdf", ErrorMessage="Incorrect file format")] 
          public HttpPostedFileBase File { get; set; }
  </code></pre>
  
  <p>However, the control still allows to upload documents of any format, why ?</p>
  
  <p>What did I missed out ?</p>