title: Input type='image' as submit button behaves differently than 'submit'
body: <p>I have multiple buttons submitting a form. I check to see which button was clicked by the input value that gets passed into my controller.</p>
  
  <pre><code>public async Task&lt;ActionResult&gt; MyAction(MyModel model, string command)
  </code></pre>
  
  <p>The html below works. In my controller <code>command</code> equals <code>myValue</code></p>
  
  <pre><code>&lt;input type="submit" name="command" value="myValue" /&gt;
  </code></pre>
  
  <p>The html below doesn't work. In my controller <code>command</code> is <code>null</code></p>
  
  <pre><code>&lt;input type="image" name="command" src="..." value="myValue"/&gt;
  </code></pre>
  
  <p><a href="http://www.w3.org/TR/2012/WD-html5-20121025/states-of-the-type-attribute.html#image-button-state-%28type=image%29" rel="nofollow">W3C says the type 'image' is a submit button</a></p>
  
  <p>So why are these two input elements behaving differently?</p>