Ajax extensions services always report “There was an error processing the request.”

I have been puzzled by the following for quite a while.

I use Microsoft Ajax extensions 1.0 to query web services which may raise exceptions. In my development environment, I would always get a nice localized error message but on the production server, the same code would produce a generic “There was an error processing the request”.

After having spent enough time stepping through my code with a debugger, I have decided to look at the Ajax extensions code and I have found the following piece of code in WriteExceptionJsonString of RestHandler.cs.

if (context.IsCustomErrorEnabled)
{
writer.Write(JavaScriptSerializer.SerializeInternal(new WebServiceError(
AtlasWeb.WebService_Error, String.Empty, String.Empty)));
}
else
{
writer.Write(JavaScriptSerializer.SerializeInternal(new WebServiceError(
ex.Message, ex.StackTrace, ex.GetType().FullName)));
}

Where WebService_Error is a resource which is valued “There was an error processing the request.”

This means that if you have enabled custom errors in your web.config on your production environment like I did, your Ajax calls will always report a generic error.

Why have the Microsoft people introduced such a restriction is a mystery to me.