Using JQGrid in conjunction with WCF Web Services

Question

I am trying to obtain the data for JQGrid from a WCF Web service that is running from within my ASP.NET 2.0 WebForms application. The problem is that the WCF Web service expects the data to be formatted as a JSON string, and JQGrid is performing an HTTP Post and passing it as Content-Type: application/x-www-form-urlencoded.

Although there appears to be several options for the format of data returned to JQGrid (it accepts JSON, XML, and others), there doesn't seem to be a way to alter the way it passes inputs to the web service.

So I'm trying to figure out how to tweak the WCF service so that it will accept

Content-Type: application/x-www-form-urlencoded

rather than

Content-Type:"application/json; charset=utf-8"

When I did a test using JQuery to send an Ajax request using url encoding (shown here):

$.ajax({
    type: "POST",
    url: "../Services/DocLookups.svc/DoWork",
    data: 'FirstName=Howard&LastName=Pinsley',
    contentType: "Content-Type: application/x-www-form-urlencoded",
    dataType: "json",
    success: function(msg) {
        alert(msg.d);
    }
});

the call fails. Using Fiddler to inspect the traffic, I found the error as returned by the server:

{"ExceptionDetail":{"HelpLink":null,"InnerException":null,"Message":
"The incoming message has an unexpected message format 'Raw'. The expected
message formats for the operation are 'Xml', 'Json'. This can be because 
a WebContentTypeMapper has not been configured on the binding. 
See the documentation of WebContentTypeMapper for more details."...

Note that this code DOES work due to the difference in encoding

$.ajax({
    type: "POST",
    url: "../Services/DocLookups.svc/DoWork",
    data: '{"FirstName":"Howard", "LastName":"Pinsley"}',
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function(msg) {
        alert(msg.d);
    }
});

On the server, the service looks like:

[ServiceContract(Namespace = "")]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
[ServiceBehavior(IncludeExceptionDetailInFaults = true)]
public class DocLookups {
    // Add [WebGet] attribute to use HTTP GET

    [OperationContract]
    public string DoWork(string FirstName, string LastName) {
        return "Your name is " + LastName + ", " + FirstName;
    }
}

and my web.config contains:

<system.serviceModel>
  <behaviors>
   <endpointBehaviors>
    <behavior name="DocLookupsAspNetAjaxBehavior">
     <enableWebScript />
    </behavior>
   </endpointBehaviors>
  </behaviors>
  <serviceHostingEnvironment aspNetCompatibilityEnabled="true" />
  <services>
   <service name="DocLookups">
    <endpoint address="" behaviorConfiguration="DocLookupsAspNetAjaxBehavior"
     binding="webHttpBinding" contract="DocLookups" />
   </service>
  </services>
</system.serviceModel>

Thanks for any help!

Answer 1

If you don't have control over your ajax call I would recommend creating and Interceptor to override the Content-Type Header.

public class ContentTypeOverrideInterceptor : RequestInterceptor
{
    public string ContentTypeOverride { get; set; }

    public ContentTypeOverrideInterceptor(string contentTypeOverride) : base(true)
    {
        this.ContentTypeOverride = contentTypeOverride;
    }

    public override void ProcessRequest(ref RequestContext requestContext)
    {
        if (requestContext == null || requestContext.RequestMessage == null)
        {
            return;
        }
        Message message = requestContext.RequestMessage;
        HttpRequestMessageProperty reqProp = (HttpRequestMessageProperty)message.Properties[HttpRequestMessageProperty.Name];
        reqProp.Headers["Content-Type"] = ContentTypeOverride;
    }
}

Then if you view your .svc file you'll see and AppServiceHostFactory class change it to include the interceptor

class AppServiceHostFactory : ServiceHostFactory
{
    protected override ServiceHost CreateServiceHost(Type serviceType, Uri[] baseAddresses)
    {
        var host = new WebServiceHost2(serviceType, true, baseAddresses);
        host.Interceptors.Add(new ContentTypeOverrideInterceptor("application/json; charset=utf-8"));
        return host;
    }
}

That should do it for you.

Update

As mentioned in the comments the method above is for use with the WCF REST Starter Kit. If you are using just a regular WCF Service you will have to create a IOperationBehavior and attached it to your service. here is the code for the behavior attribute

public class WebContentTypeAttribute : Attribute, IOperationBehavior, IDispatchMessageFormatter
{
    private IDispatchMessageFormatter innerFormatter;
    public string ContentTypeOverride { get; set; }

    public WebContentTypeAttribute(string contentTypeOverride)
    {
        this.ContentTypeOverride = contentTypeOverride;
    }


    // IOperationBehavior
    public void Validate(OperationDescription operationDescription)
    {

    }

    public void ApplyDispatchBehavior(OperationDescription operationDescription, DispatchOperation dispatchOperation)
    {
        innerFormatter = dispatchOperation.Formatter;
        dispatchOperation.Formatter = this;
    }

    public void ApplyClientBehavior(OperationDescription operationDescription, ClientOperation clientOperation)
    {

    }

    public void AddBindingParameters(OperationDescription operationDescription, BindingParameterCollection bindingParameters)
    {

    }

    // IDispatchMessageFormatter
    public void DeserializeRequest(Message message, object[] parameters)
    {
        if (message == null)
            return;

        if (string.IsNullOrEmpty(ContentTypeOverride))
            return;

        var httpRequest = (HttpRequestMessageProperty)message.Properties[HttpRequestMessageProperty.Name];
        httpRequest.Headers["Content-Type"] = ContentTypeOverride;
    }

    public Message SerializeReply(MessageVersion messageVersion, object[] parameters, object result)
    {
        return innerFormatter.SerializeReply(messageVersion, parameters, result);
    }
}

And you would have to modify your Service contract to look like this one

[OperationContract]
[WebContentType("application/json; charset=utf-8")]
public string DoWork(string FirstName, string LastName)
{
    return "Your name is " + LastName + ", " + FirstName;
}

Links

As you requested here are some links describing these WCF Extensions

• IOperationBehavior Interface
• IDispatchMessageFormatter Interface
• How to get implementation of IDispatchMessageFormatter
• WCF Extensibility - Plugging in custom message processing logic