title: 400 Bad request when trying to contact WCF service using XHR
body: <p>I'm making a WCF web service that will return a json object, but I keep getting a 400 bad request error when I try to make an AJAX call:</p>
  
  <pre><code>OPTIONS http://localhost:55658/WebServiceWrapper.svc/GetData?_=1318567254842&amp;value=97            HTTP/1.1
  Host: localhost:55658
  User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:7.0.1) Gecko/20100101 Firefox/7.0.1
  Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
  Accept-Language: en-us,en;q=0.5
  Accept-Encoding: gzip, deflate
  Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
  DNT: 1
  Connection: keep-alive
  Origin: http://localhost:3000
  Access-Control-Request-Method: GET
  Access-Control-Request-Headers: content-type
  
  HTTP/1.1 400 Bad Request
  Server: ASP.NET Development Server/10.0.0.0
  Date: Fri, 14 Oct 2011 04:40:55 GMT
  X-AspNet-Version: 4.0.30319
  Cache-Control: private
  Content-Length: 0
  Connection: Close
  </code></pre>
  
  <p>Here is my AJAX call:</p>
  
  <pre><code>$.ajax({
    contentType: 'application/json',
    url: 'http://localhost:55658/WebServiceWrapper.svc/GetData',
    dataType: 'json',
    data: {
      value: 97
    },
    success: function (data) {
      alert('success' + data);
    },
    error: function(XMLHttpRequest, textStatus, errorThrown) {
      alert('failure' + errorThrown);
    }
  });
  </code></pre>
  
  <p>Here is my WCF service definition:</p>
  
  <pre><code>public class WebServiceWrapper : IWebServiceWrapper
  {
      public object GetData(int value)
      {
          return new 
          {
              ReturnValue = string.Format("You entered: {0}", value)
          };
      }
  }
  </code></pre>
  
  <p>And it's interface:</p>
  
  <pre><code>[ServiceContract]
  public interface IWebServiceWrapper
  {
      [OperationContract]
      object GetData(int value);
  }
  </code></pre>
  
  <p>I know I've solved this problem before, but I can't remember what I had done before. Any help would be greatly appreciated as the hole I'm putting in the wall is just getting bigger and bigger.</p>