Send a GridView to Excel when a button is clicked.

Add EnableEventValidation="false" to <%@ Page %> tag.

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Response.Clear()
        Response.AddHeader("content-disposition", "attachment; filename=FileName.xls")
        Response.Charset = ""
        ' If you want the option to open the Excel file without saving than
        ' comment out the line below
        ' Response.Cache.SetCacheability(HttpCacheability.NoCache);
        Response.ContentType = "application/vnd.xls"
        Dim stringWrite As New System.IO.StringWriter()
        Dim htmlWrite As System.Web.UI.HtmlTextWriter = New HtmlTextWriter(stringWrite)
        GridView1.RenderControl(htmlWrite)
        Response.Write(stringWrite.ToString())
        Response.End()
    End Sub

    Public Overrides Sub VerifyRenderingInServerForm(ByVal control As Control)
        'Confirms that an HtmlForm control is rendered for the specified ASP.NET server control at run time. 
        'This is required in order to send data to Excel.
    End Sub