linq 把list分组为 List<List>

public class User
{
  public int UserID { get; set; }
  public string UserName { get; set; }
  public int GroupID { get; set; }
}

List<User> userList = new List<User>();
userList.Add( new User { UserID = , UserName = "UserOne", GroupID =  } );
userList.Add( new User { UserID = , UserName = "UserTwo", GroupID =  } );
userList.Add( new User { UserID = , UserName = "UserThree", GroupID =  } );
userList.Add( new User { UserID = , UserName = "UserFour", GroupID =  } );
userList.Add( new User { UserID = , UserName = "UserFive", GroupID =  } );
userList.Add( new User { UserID = , UserName = "UserSix", GroupID =  } );

GroupedUserList
    UserList
        UserID = , UserName = "UserOne", GroupID =
        UserID = , UserName = "UserTwo", GroupID =
        UserID = , UserName = "UserFour", GroupID =
    UserList
        UserID = , UserName = "UserThree", GroupID =
    UserList
        UserID = , UserName = "UserFive", GroupID =
        UserID = , UserName = "UserSix", GroupID = 

var groupedLATABLEList = list
.GroupBy(u => u.Type)
.Select(grp => new
{
Key = grp.Key,
List = grp.ToList()
})
.ToList();