Entity framework c# error on updating a record

Question

I am getting the error "The relationship between the two objects cannot be defined because they are attached to different ObjectContext objects." when updating the Permission record with UserRoles navigation.

 

var permission = _permissionService.GetPermissionRecordBySystemName(permissionSystemName);

if (permission != null)

{

var userRole = _userService.GetUserRoleById(roleId);

if (permission.UserRoles.Contains(userRole))

{

permission.UserRoles.Remove(userRole);

}

else

{

permission.UserRoles.Add(userRole);

}

_permissionService.Update(permission); // Error at this line

}

 

I have used UnityContainer and repository pattern.