Function to Fill data in Combobox control in vb.net

 public Boolean FillCombo(ref DropDownList DD1, string DisplayColumn, string ValuColumn, string TableName)
    {
        try
        {
            string QueryString = "";
            QueryString = "select " + DisplayColumn + "," + ValuColumn + " from " + TableName + " order by " + DisplayColumn;
            cmd = new SqlCommand(QueryString, ObjCn.OpenDb());
            DA = new SqlDataAdapter(cmd);
            DtMain = new DataTable(TableName);
            DA.Fill(DtMain);
            DD1.DataTextField = DisplayColumn;
            DD1.DataValueField = ValuColumn;
            DD1.DataSource = DtMain;
            DD1.DataBind();
            ListItem LtSelect = new ListItem("Select", "0");
            DD1.Items.Insert(0, LtSelect);
            return true;
        }
        catch (Exception ex)
        {
            return false;
        }
        finally
        {
            ObjCn.CloseDB();
            cmd.Dispose();
            DA.Dispose();
        }
    }