I am trying to be a good chap and work with objects. So, I am returning a list of Users (with GroupIDs) to the front end from my DataAccess class ...

Code:
public List<DataObjects.User> getUsers()
    {
        List<DataObjects.User> myUserList = new List<DataObjects.User>();
        SqlConnection myConnection = new SqlConnection(connectionString);
        SqlCommand myCommand = myConnection.CreateCommand();
        SqlDataReader dr;
        myCommand.CommandText = "Users_List";
        myCommand.CommandTimeout = 120;
        myCommand.Connection = myConnection;
        myCommand.CommandType = CommandType.StoredProcedure;

        myConnection.Open();
        dr = myCommand.ExecuteReader(CommandBehavior.CloseConnection);

        if (dr.HasRows)
        {
            while (dr.Read())
            {
                DataObjects.User myUser = new DataObjects.User();
                myUser.UserID = dr["UserID"].ToString();
	myUser.UserName = dr["UserName"].ToString();
                myUser.GroupID = dr["GroupID"].ToString();
                myUserList.Add(myUser);
            }
        }

        return myUserList;
    }
In the front end I am populating a Gridview with a list of Users (from a separate DataSource. As I go through the Gridview - in certain conditions - I want to be able to retrieve which GroupIDs the User belongs to from the list above.

How do I access the list in the front end. I have used Lists before but in the front end I have always used them as the DataSource for a control. Now I just want to be able to filter the List and retrieve the filtered data from the list. How do I do this? Thanks for any help.