How to export all pages of gridview to excel without columns containing controls?

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C#

ASP.NET

C#4.0

Gridview

export

I have a gridview that has 2 columns that are a dropdownlist and upload control. I am trying to export the gridview to excel and the code works but it only works to export the current view not all the pages. When I try to export all pages the data binding fails and code crashes. Please help if you know a way of getting all the pages exported to excel/csv with or without the columns containing controls. Thank you! Amilah
Here is my code:

protected void ExportBtn_Click(object sender, ImageClickEventArgs e)
    {
        
        gv.Columns[7].Visible = false;
        gv.Columns[8].Visible = false;
        
        Response.ClearContent();
        Response.AppendHeader("content-disposition", "attachment; filename=Documents.xls");
        Response.ContentType = "application/excel";
        gv.AllowPaging = false;
        gv.DataBind();

        StringWriter sw = new StringWriter();
        HtmlTextWriter htw = new HtmlTextWriter(sw);
                
        Response.Charset = String.Empty;

        gv.RenderControl(htw);
        Response.Write(sw.ToString());
        
        Response.End();
    }