merge cell header แล้ว export to excel แล้ว ส่วนที่แทรกเข้ามาไปเข้าไปใน excel

using System; 
using System.Data; 
using System.Configuration; 
using System.IO; 
using System.Web; 
using System.Web.Security; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
using System.Web.UI.WebControls.WebParts; 
using System.Web.UI.HtmlControls; 
 
 
public class GridViewExportUtil 
{ 
 
    public static void Export(string fileName, GridView gv) 
    { 
        HttpContext.Current.Response.Clear(); 
        HttpContext.Current.Response.AddHeader( 
            "content-disposition", string.Format("attachment; filename={0}", fileName)); 
        HttpContext.Current.Response.ContentType = "application/ms-excel"; 
 
        using (StringWriter sw = new StringWriter()) 
        { 
            using (HtmlTextWriter htw = new HtmlTextWriter(sw)) 
            { 
                //  Create a form to contain the grid 
                Table table = new Table(); 
 
                //  add the header row to the table 
                if (gv.HeaderRow != null) 
                { 
                    GridViewExportUtil.PrepareControlForExport(gv.HeaderRow); 
                    table.Rows.Add(gv.HeaderRow); 
                } 
 
                //  add each of the data rows to the table 
                foreach (GridViewRow row in gv.Rows) 
                { 
                    GridViewExportUtil.PrepareControlForExport(row); 
                    table.Rows.Add(row); 
                } 
 
                //  add the footer row to the table 
                if (gv.FooterRow != null) 
                { 
                    GridViewExportUtil.PrepareControlForExport(gv.FooterRow); 
                    table.Rows.Add(gv.FooterRow); 
                } 
 
                //  render the table into the htmlwriter 
                table.RenderControl(htw); 
 
                //  render the htmlwriter into the response 
                HttpContext.Current.Response.Write(sw.ToString()); 
                HttpContext.Current.Response.End(); 
            } 
        } 
    } 
 
    /// <summary> 
    /// Replace any of the contained controls with literals 
    /// </summary> 
    /// <param name="control"></param> 
    private static void PrepareControlForExport(Control control) 
    { 
        for (int i = 0; i < control.Controls.Count; i++) 
        { 
            Control current = control.Controls[i]; 
            if (current is LinkButton) 
            { 
                control.Controls.Remove(current); 
                control.Controls.AddAt(i, new LiteralControl((current as LinkButton).Text)); 
            } 
            else if (current is ImageButton) 
            { 
                control.Controls.Remove(current); 
                control.Controls.AddAt(i, new LiteralControl((current as ImageButton).AlternateText)); 
            } 
            else if (current is HyperLink) 
            { 
                control.Controls.Remove(current); 
                control.Controls.AddAt(i, new LiteralControl((current as HyperLink).Text)); 
            } 
            else if (current is DropDownList) 
            { 
                control.Controls.Remove(current); 
                control.Controls.AddAt(i, new LiteralControl((current as DropDownList).SelectedItem.Text)); 
            } 
            else if (current is CheckBox) 
            { 
                control.Controls.Remove(current); 
                control.Controls.AddAt(i, new LiteralControl((current as CheckBox).Checked ? "True" : "False")); 
            } 
 
            if (current.HasControls()) 
            { 
                GridViewExportUtil.PrepareControlForExport(current); 
            } 
        } 
    } 
}