C# - TryUpdateModel Not Working With Prefix And IncludeProperties

i have an entity called User with 2 properties called UserName and Role (which is a reference to another entity called Role). I'm trying to update the UserName and RoleID from a form which is posted back. Within my postback action i have the following code:

var user = new User();

TryUpdateModel(user, "User", new string[] { "UserName, Role.RoleID" });

TryUpdateModel(user, new string[] { "User.UserName, User.Role.RoleID" });

However none of these updates the Role.RoleID property. If i try the following:

TryUpdateModel(user, "User", new string[] { "UserName, Role" });

TryUpdateModel(user);

The RoleID is updated but the RoleName property is validated aswell. That's why i'm trying to be more specific on which properties to update but i can't get any of the first examples to work.