Could you please help me to use or add systemuserroles_association in CRM 2011

Question

Hi All,

I have a silverlight application running as part of web
resource inside CRM 2011.

I am using DataServiceContext to talk to CRM from
Silverlight

I am able to make any query, add or update the entity
through DataServiceContext.

User is already created, Role is already created using UI
interface.

Using REST CRM Silverlight programming:

However, when I try to associate SystemUser to a specific
role by using addLink(user, "systemuserroles_association", role),
I always get an exception message saying that "Invalid role specified for
entity 'systemuser' in relationship systemuserroles_association.Referenced"

user.systemuserroles_association.Add(role);

Or

role.systemuserroles_association.Add(user);

I am always getting an exception message saying that
"Invalid role specified for entity 'systemuser' in relationship
systemuserroles_association.Referenced"

Could you please help me to use or add
systemuserroles_association.

Thanks with kind regards,

Mohan Swargam