title: ASP.NET MVC 4.5 OnBlur event TextBox
body: <p>I have a C# ASP.net MVC 4.5 solution. I want to create a form with automated address validation.
  If you enter a zipcode and housenumber the streetname en city is looked up using an external REST API. </p>
  
  <p>After filling in the housenumber there must be a call to a function in a controller (using AJAX) to look up the address, update the model data and show the result in the form. I can't figure out how to do this. </p>
  
  <p>I was thinking about doing a form post (using AJAX) fired when the onBlur from the housenumber is called. But is this the best way ? Is it really the best way is posting back the whole form ?</p>
  
  <p>Example so far:</p>
  
  <pre><code>&lt;div class="col-md-7"&gt;
   @Html.TextBoxFor(model =&gt; model.HouseNumber, new { @class = "form-control", @placeholder = "HouseNumber" })
   @Html.ValidationMessageFor(model =&gt; model.HouseNumber, null, new { @class = "text-danger" })
  &lt;/div&gt;
  </code></pre>
  
  <p>When the TextBox HouseNumber lost focus I want to call the function 'ValidateAddress' in my controller 'AddressBook'. The function will lookup the streetname and city and will fill the model.Streetname and model.City fields.</p>