Stored Procedure Driven Data Grid

using System;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;

public partial class Basic : System.Web.UI.Page 
{
    public GridFormatter gf;    //will be initialized in "Button_Query_Click", and will be called from "gvMain_RowDataBound"

    protected void Page_Load(object sender, EventArgs e)
    {
        this.gvMain.RowDataBound += new GridViewRowEventHandler(gvMain_RowDataBound);

        this.Label_Info.Text = "";

        if (!IsPostBack)
        {
            this.TextBox_StartsOn.Text = "2010-3-1";
            this.TextBox_EndsOn.Text = string.Format("{0:yyyy-MM-dd}", DateTime.Now);

            Button_Query_Click(null, null);
        }
    }

    protected void Button_Query_Click(object sender, EventArgs e)
    {
        string _sql = string.Format("EXEC spListDeliveryForServerSide '{0}', '{1:yyyyMMdd}', '{2:yyyyMMdd} 23:59:59'",
                this.TextBox_SearchCriteria.Text,
                DateTime.Parse(this.TextBox_StartsOn.Text),
                DateTime.Parse(this.TextBox_EndsOn.Text));

        using (SqlConnection sqlConn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["DB_CONNECTION_STRING"].ConnectionString))
        {
            SqlDataAdapter sqlDa = new SqlDataAdapter(_sql, sqlConn);
            DataTable dt = new DataTable();
            sqlDa.Fill(dt);

            if (dt.Rows.Count > 0)
            {
                gf = new GridFormatter(dt);

                this.gvMain.DataSource = dt.DefaultView;
                this.gvMain.DataBind();
                //
                // CSS support
                this.gvMain.HeaderRow.CssClass = "dyn_grid_header";
                this.gvMain.RowStyle.CssClass = "dyn_grid_row";
                this.gvMain.AlternatingRowStyle.CssClass = "dyn_grid_row_alternate";
                //
                // Set the footer summary row
                gf.SetSummaryColumns(ref this.gvMain);

                this.Label_Info.Text = string.Format("{0:n0} row(s)", dt.Rows.Count);
            }
            else
            {
                this.gvMain.DataSource = null;
                this.gvMain.DataBind();

                this.Label_Info.Text = "No Row found";
            }
        }
    }

    protected void gvMain_RowDataBound(object sender, System.Web.UI.WebControls.GridViewRowEventArgs e)
    {
        gf.HandleRowDataBoundEvent(this.Page, ref this.gvMain, e.Row);
    }
}