Passing a parameter from the Telerik RadToolTipManager to a WCF service fails

When the RadToolTipManager calls the WCF web service it fails when trying to cast to an IDictionary contextDictionary where as when the web service is just a pure webservice the parameter correctly casts.

Why is this?

The code in questi开发者_StackOverflow中文版om

[WebMethod]
public string WebServiceMethodName(object context)
{
    // works
    IDictionary<string, object> contextDictionary = (IDictionary<string, object>) context;

}

[OperationContract]
public string WebServiceMethodName(object context)
{
    // fails
    IDictionary<string, object> contextDictionary = (IDictionary<string, object>) context;

}

Use Fiddler (http://www.fiddler2.com/fiddler2) to see the exact error message returned.