How to download a dynamically generated file from server to client from a webpart?

Question

I have a webpart that needs to create dynamically a .zip file in the server and download that file to the client machine, once the user clicks on an Export button.

The .zip generation is ready, I just need to know how to download the file to the client machine, in a way the user chooses the destination directory. I saw 2 main different solutions over the internet: one uses the Response.TransmitFile/WriteFile, and the other one involves creating a download page. Is there a easiest way to do this directly from the code behind?

Answer 1

Assuming you have the MemoryStream, the below code will bring the Save Dialog so user can choose the path

Byte[] byteArray = memoryStream.ToArray();
memoryStream.Flush();
memoryStream.Close();
Response.Clear();
Response.ClearHeaders();
Response.AddHeader("Content-Disposition","attachment; filename=filename.zip");
Response.ContentType = "application/octet-stream";
Response.BinaryWrite(byteArray);
Response.End();

Fix for non-responsive events

Change your Export button as follows

<asp:Button ID="btnExport" runat="server" Text="Export" OnClick="Export_Click" OnClientClick="javascript:setFormSubmitToFalse()" />

Add this JavaScript function to the ASCX file

function setFormSubmitToFalse() {
    setTimeout(function () { _spFormOnSubmitCalled = false; }, 1000);
    return true;
}

Answer 2

In the event handler of your Export button use this code

Response.AddHeader("Content-disposition", "attachment; filename=YourFile.zip");
Response.ContentType = "application/octet-stream";
Response.BinaryWrite(bytes); //bytes is byte[] of your zip file
Response.End();