title: System.FormatException Exception Adding User Agent in Windows phone 8
body: <p>I want to use the following user agent in a windows phone 8 application</p>
  
  <pre><code>string userAgentString = "Mozilla/5.0 (compatible; MSIE 10.0; Windows Phone " + Environment.OSVersion.Version.ToString();
  userAgentString += "; Trident/6.0; IEMobile/10.0; ARM; Touch; " + Microsoft.Phone.Info.DeviceStatus.DeviceManufacturer + ";";
  userAgentString += Microsoft.Phone.Info.DeviceStatus.DeviceName;
  httpClient.DefaultRequestHeaders.UserAgent.ParseAdd(userAgentString);
  </code></pre>
  
  <p>but I am getting a System.FormatException, How do I properly format the user agent string. The string is suppose to be of this form: </p>
  
  <pre><code>Mozilla/5.0 (compatible; MSIE 10.0; Windows Phone 8.0; Trident/6.0; IEMobile/10.0; ARM; Touch; NOKIA; Lumia 920)  
  </code></pre>
  
  <p>this is the exception </p>
  
  <pre><code>A first chance exception of type 'System.FormatException' occurred in System.Net.Http.DLL
     at System.Net.Http.Headers.HttpHeaderParser.ParseValue(String value, Object storeValue, Int32&amp; index)
     at System.Net.Http.Headers.HttpHeaders.ParseAndAddValue(String name, HeaderStoreItemInfo info, String value)
     at System.Net.Http.Headers.HttpHeaders.Add(String name, String value)
     at System.Net.Http.Headers.HttpHeaderValueCollection`1.ParseAdd(String input)
     at MyApp.Assets.Class.MyAppNetUtils.&lt;GetRemoteStringContent&gt;d__0.MoveNext()
  </code></pre>