Exporting data as a CSV and allow download from browser C#

I recently did some work to export a data table as a Comma Separated Variable file or a MDB file.

The following code allows you to generate a csv from a data table.

   1: public static void CreateCSVHelper(DataTable sourceTable)

   2: {

   3:     //locals

   4:     StringBuilder outputBuilder = new StringBuilder();

   5:     

   6:     //write column names        

   7:     for (int i = 0; i < sourceTable.Columns.Count; i++)

   8:     {

   9:         if (i > 0)

  10:             outputBuilder.Append(",");

  11:         outputBuilder.Append(sourceTable.Columns[i].ColumnName);        

  12:     }

  13:     outputBuilder.Append(Environment.NewLine);

  14:     

  15:     //Put in data

  16:     foreach (DataRow row in sourceTable.Rows)

  17:     {

  18:         for (int i = 0; i < sourceTable.Columns.Count; i++)

  19:         {       

  20:             if (i > 0)

  21:                 outputBuilder.Append(",");                     

  22:             outputBuilder.Append(string.Format("\"{0}\"",row[i].ToString()));           

  23:         }

  24:         

  25:         outputBuilder.Append(Environment.NewLine);

  26:     }

  27:  

  28:     try

  29:     {

  30:         //Attempt to write file

  31:         StreamWriter sw = new StreamWriter(filename);

  32:         sw.Write(outputBuilder.ToString());

  33:         sw.Close();

  34:     }

  35:     catch (Exception ex)

  36:     {

  37:         System.Diagnostics.Debug.Write(ex);

  38:     }

  39: }

To display a link through to a browser, i.e. provide a link on a page where the user can click, get prompted do you wish to open or save this file – put the following in the code behind of the relevant page.

   1: protected void btnExportCSV_onClick(object sender, EventArgs e)

   2: {

   3:     //Clear buffer

   4:     Response.Clear();

   5:  

   6:     //Tell the browser it expects to get text output in the form of a csv

   7:     Response.ContentType = "text/csv";

   8:  

   9:     //Append header to tell the browser to expect a file

  10:     Response.AppendHeader("Content-Disposition", string.Format("attachment; filename={0}", filename));

  11:     

  12:     //Send file to browser response stream

  13:     Response.TransmitFile(filepath);

  14:  

  15:     //End the response 

  16:     Response.End();

  17: }

Finally if you are trying to use the code inside an update panel you will need to set the export button as a postback trigger. This can either be done using the following asp.net markup:

   1: <asp:UpdatePanel ID="upExport" runat="server">  

   2:     <ContentTemplate>  

   3:         <asp:LinkButton ID="btnExportCSV" runat="server">Export To Excel</asp:LinkButton>  

   4:     </ContentTemplate>  

   5:     <Triggers>  

   6:         <asp:PostBackTrigger ControlID="btnExportCSV">  

   7:         </asp:PostBackTrigger>  

   8:     </Triggers>  

   9: </asp:UpdatePanel>  

or you can set it dynamically in the code behind with the following lines put into the page_load event.

   1: //Deal with postback 

   2: smExportCSV.RegisterPostBackControl(btnExportCSV);

Where smExportCSV is your script manager control.