Updating a table with a composite primary key using LINQ

I have a table named tblUserNetwork

. It contains composite primary key

on UserID

andConnectedToUserID

When I update the table networks.Update(networks)

, it gives an error like this:

Table dbo.tblUserNetwork contains a composite primary key field

      

        
        
        
      

    

What is the problem with the update.

I update many other tables, they don't have a composite primary key that they update well and well. But this is not the case, I cannot understand this problem.

Is there an ant issue with composite primary key