Cортировка в GridView

    private string GetSortDirection(string column)
    {
        // By default, set the sort direction to ascending.
        SortDirection direction = SortDirection.Ascending;
        string sortExp = "";
        
        if (RadioButton1.Checked == true)
        {
            sortExp = "id";
            table.Sort(sortExp, direction);
           
            // Save new values in ViewState.
            ViewState["SortDirection"] = direction;
            ViewState["SortExpression"] = sortExp;
            column = ViewState["SortExpression"] as string;
        }
        else if (RadioButton2.Checked == true)
        {
            sortExp = "FIO";
            
            table.Sort(sortExp, direction);
            // Save new values in ViewState.
            ViewState["SortDirection"] = direction;
            ViewState["SortExpression"] = sortExp;
            column = ViewState["SortExpression"] as string;
        }
 
        //return direction;
    }
 
    protected void Headlines_Sorting(object sender, GridViewSortEventArgs e)
    {
        //Retrieve the table from the session object.
        DataTable dt = (DataTable)Cache["table"];
 
        if (dt != null)
        {
            
            //Sort the data.
            dt.DefaultView.Sort = e.SortExpression + " " + GetSortDirection(e.SortExpression);
 
            // Re-cache the updated DataTable.
            Cache["table"] = dt;
        }
     }