RegisterStartupScript() is not mixing well with the back button, suggestions?

Question

Given an ASP.NET 2.0 page with the following code in a button click event...

Protected Sub btnQuickRpt_Click(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles btnQuickRpt.Click
  Dim uniqueReportId As String = GenerateQuickReport()

  ' Opens the report on page reload.
  ClientScript.RegisterStartupScript(Me.GetType(), "openReport", "window.open('Reports/" & uniqueReportId & ".pdf');", True)
End Sub

After clicking the button associated with this code the window.open() code is run when the page is reloaded properly. However, if after that, the user navigates to another URL and then clicks the browser's back button, the "window.open()" code happens again making the user's report pop back up, unexpectedly, in their face.

Based on suggestions from similar style threads, I've toyed around with setting the cacheability of the page, but no combination produced the expected result of returning to this page, without prompt and without the window.open() code executing again.

Does anyone have a suggestion on how to handle this situation?

Answer 1

Instead of using a server button to generate the report before the window is opened, use client script in a button to open the window with a page that creates the report and returns it in the response.

Create a page (for example GenerateReport.aspx) that generates the report and returns it directly in the response stream. In the Page_Load method:

Dim uniqueReportId As String = GenerateQuickReport()
Response.Clear();
Response.ContentType = "application/pdf";
Response.WriteFile(Server.MapPath("Reports/" & uniqueReportId & ".pdf"));
Response.End();

Now you just open that page from a button:

<input type="button" value="gimme teh repport!" onclick="window.open('GenerateReport.aspx','_blank');"/>

You can use an http handler instead of a regular page, it fit's a little better for what you do, but I showed you how to do it with a regular page as that is probably more familiar.

If you can create the report in memory instead of as a file, you can return it using Response.BinaryWrite so that you don't have to create the files at all.