Problem with Excel export

Question

Hi!
I am trying to export data from datagrid to Excel. Export goes just fine, but the page I make the export from stops responding. I.E. pressing the export button again won't do anything. After reload (by pressing F5) page it works normally until the next export. I made a simple code example that demonstrates the problem:
    public class ExcelTesti : System.Web.UI.WebControls.WebParts.WebPart
        Button excelButton = new Button();
        public ExcelTesti()
            this.ExportMode = WebPartExportMode.All;
        protected override void Render(HtmlTextWriter writer)
            excelButton.RenderControl(writer);
        protected override void CreateChildControls()
            excelButton.Text = "To Excel";           
            this.Controls.Add(excelButton);      
            excelButton.Click += new EventHandler(m_button_Click);
        protected void m_button_Click(object sender, EventArgs e)
            this.Page.Response.Clear();
            this.Page.Response.AddHeader("content-disposition", "attachment;filename=PIexport.xls");
            this.Page.Response.Cache.SetCacheability(HttpCacheability.NoCache);
            this.Page.Response.ContentType = "application/vnd.ms-excel";
            Page.Response.BufferOutput = true;
            this.Page.Response.Buffer = true;
            EnableViewState = false;
            this.Page.Response.Charset = "";
            StringWriter strW = new StringWriter();
            HtmlTextWriter htmlw = new HtmlTextWriter(strW);
            htmlw.RenderBeginTag(HtmlTextWriterTag.Table);
            htmlw.RenderBeginTag("tr"); //Add a row
            htmlw.RenderBeginTag("td"); // Add a cell
            htmlw.Write("Test");
            htmlw.RenderEndTag(); //End of the cell tag
            htmlw.RenderEndTag(); //End of the row tag
            htmlw.RenderEndTag(); //End <Table>           
            this.Page.Response.Write(strW.ToString());
            Page.Response.Flush();
            Page.Response.End();
I found some threads with the same problem, but no solutions that helped me. For example
http://forums.microsoft.com/TechNet/ShowPost.aspx?PostID=1572942&SiteID=17
http://forums.microsoft.com/TechNet/ShowPost.aspx?PostID=1369245&SiteID=17
There must be some way to do this. I have seen web parts that do this right.
Can anyone help me?
Antti

Answer 1

Hi,
         I am facing with the same issue. I think it is absolutely with Response.Clear(), which removing all the events and hence page is not reepsonding to any event.
         I have a deployed a custom- webpart in to a sharepoint site, which is consisting of a summary html table, button control and Export to Excel button. Every thing is working except events are not fired after export to excel button is clicked. The code inside the export to excel is
Export to Excel Click event code:
Me.Page.Response.Clear() 'clear the response before writing excel stream
Me.Page.Response.ContentType = "application/vnd.ms-excel" 'set the response contenttype as excel
Me.Page.Response.Charset = String.Empty 'set response charset as string
'get the filename to be displayed on the response stream
'specifying the response stream as an attatchment in the header [to open the excel file in the seperate window]
Me.Page.Response.AddHeader("Content-Disposition", "attachment;filename=test.xls")
'write the content on to the screen
Me.Page.Response.Write(sbExcelString.ToString()) 'writing excel stream in the form of string
'end the response once done [otherwise unnecessary conent will be appended at the end of the excel file]
Me.Page.Response.End()
I think somewhere the issue with Response.Clear or Response.End.
As you said there is a remedy for this, but i cant use that remedy because i cannot use a new page becauce my code is entirely in to a custom control and i should not depend on any aspx page.
Please help out in solving this issue in the same custom control click event itself.
I think there is a solution, only thing how to attach the events when we use Response.Clear or Response.End method [but i dont know how do i do this].
Thanks in advance for your helpful message.
Mukthesh.