How to natively enable JSONP for existing WCF service?

Question

I have a an existing service like the below method:

[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
[ServiceBehavior(AddressFilterMode = AddressFilterMode.Any)]
public class SomeService : ISomething
{
    public SomeListResults SomeList(SomeParams someParams)
    {
          ....
    }
}

Is there a simple way to allow JSONP calls and also JSON at the same time (detect it). Is this native?

Answer 1

Update your config to look like:

<configuration>
  <system.web>
    <compilation debug="true" targetframework="4.0">
    <authentication mode="None">
  </authentication></compilation></system.web>
  <system.webserver>
    <modules runallmanagedmodulesforallrequests="true">
  </modules></system.webserver>
  <system.servicemodel>
    <servicehostingenvironment **aspnetcompatibilityenabled**="true">
    <standardendpoints>
      <webscriptendpoint>
        <standardendpoint **crossdomainscriptaccessenabled**="true" name="">
      </standardendpoint></webscriptendpoint>
    </standardendpoints>
  </servicehostingenvironment></system.servicemodel>
</configuration>

See here for a blog post providing a walkthrough of creating a wcf service that's accessible cross-domain.

This will enable your service to accept requests from cross-domain sources.

In terms of determining whether to pad your response (the p in jsonp),

Thanks to @carlosfigueira for this:

If using .Net 4 JSONP is supported natively. As long as the request has a query string parameter called "callback" (this name can be configured), the response will be padded with the function name .

Otherwise, you'll need to write a custom message inspector that pads the response appropriately.