How to open new window with streamed document in ASP.NET Web Forms - asp.net

Question

I have an ASP.NET Web Forms application. I want to have a button to post back to the server that will use my fields on my form (after validation) as parameters to a server process that will generate a document and stream it back to the browser. I want the form to be updated with some status results.
What is the best way to achieve this? Right now, I've got the button click generating the document and streaming it back to the browser (it's a Word document and the dialog pops up, and the Word document can be opened successfully) but the page doesn't get updated.
I have jQuery in my solution, so using js isn't an issue if that is required.

Answer 1

I have a very similar process on one of my servers, and the way I've handled it is to create a temporary document on the server rather than doing a live stream. It requires a bit of housekeeping code to tidy it up, but it does mean that you can return the results of the generation and then do a client-side redirect to the generated document if successful. In my case, I'm using jQuery and AJAX to do the document generation and page update, but the same principle should also apply to a pure WebForms approach.

Answer 2

This was way more difficult to do than I thought. The main issue is with opening a new browser window for a Word document. The window briefly flashes up, then closes - no Word document appears. It seems to be a security issue.
If i click a button on my page, I can stream the Word doc back as the response, and the browser dialog pops up allowing me to Open/Save/Cancel, but of course, my page doesn't refresh.
My final solution to this was to use a client script on the button click to temporarily set the form's target to _blank. This forces the response to the click on the postback to go to a new browser window (which automatically closes after the download dialog is dismissed):
<asp:Button Text="Generate Doc" runat="server" ID="btnGenerateDoc"
onclick="btnGenerateDoc_Click" OnClientClick="SetupPageRefresh()" />
My SetupPageRefresh function is as follows:
function SetupPageRefresh() {
// Force the button to open a new browser window.
form1.target = '_blank';
// Immediately reset the form's target back to this page, and setup a poll
// to the server to wait until the document has been generated.
setTimeout("OnTimeout();", 1);
}
Then my OnTimeout function resets the target for the form, then starts polling a web service to wait until the server process is complete. (I have a counter in my Session that I update once the process has completed.)
function OnTimeout() {
// Reset the form's target back to this page (from _blank).
form1.target = '_self';
// Poll for a change.
Poll();
}
And the Poll function simply uses jQuery's ajax function to poll my web service:
function Poll() {
var currentCount = $("#hidCount").val();
$.ajax({
url: "/WebService1.asmx/CheckCount",
data: JSON.stringify({ currentCount: currentCount }),
success: function (data) {
var changed = data.d;
if (changed) {
// Change recorded, so refresh the page.
window.location = window.location;
}
else {
// No change - check again in 1 second.
setTimeout("Poll();", 1000);
}
}
});
}
So this does a 1 second poll to my web service waiting for the Session's counter to change from the value in the hidden field on the page. This means it doesn't matter how long the server process takes to generate the Word document (and update the database, etc.) the page won't refresh until it's done.
When the web service call comes back with true, the page is refreshed with the window.location = window.location statement.
For completeness, my Web Service looks like this:
/// <summary>
/// Summary description for WebService1
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.ComponentModel.ToolboxItem(false)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line.
[System.Web.Script.Services.ScriptService]
public class WebService1 : WebService
{
[WebMethod(EnableSession=true)]
public bool CheckCount(int currentCount)
{
if (Session["Count"] == null)
Session["Count"] = 0;
var count = (int)Session["Count"];
var changed = count != currentCount;
return changed;
}
}
Hopefully that helps somebody else!