VB.NET - registerstartupscript then redirect to same page

Question

I have inherited a .NET 4.0 application that uses some forms with buttons that call Oracle procedure. Often, before postback caused by pressing those buttons, RegisterStartupScript is used to show an alert after the execution, so after page refresh.

Now, I would like to disable re-submitting the form when the user presses F5 or refreshes the page, and I found that the most straightforward method is to use Response.Redirect to the same page instead of postback. So, I tried the following:

Protected Sub btnButton_Click(sender As Object, e As System.EventArgs) Handles btnButton.Click
   Try
      ' Do something (call Oracle procedure)

      Dim TheScript As New StringBuilder
      TheScript.Append("<script language=JavaScript>alert(""Success!"");</script>")
      ClientScript.RegisterStartupScript(GetType(String), "ShowInfoPage", TheScript.ToString)

   Catch ex As Exception
      ' Do something
   End Try

   Response.Redirect(Request.Url.ToString(), False)
End Sub

but the alert (obviously) is not fired after page reload.

At this point I have two questions:

1. is there a quick way to make sure that the redirect does not involve the loss of the script recorded with RegisterStartupScript? For "quick" I mean for example "Use Transfer instead of Redirect" or something that does not involve the rewriting of the alert management code;
2. to do not add Response.Redirect in every part of the code, how I can intercept any postback request in order to replace it with a redirect to the same page that requested the postback? I thought of something like HttpModule or something like that, although I have not much experience on this (sorry if I said something senseless).

Thanks

Answer 1

The easiest methods are using a QueryString parameter or a Session to "store" that the event has been triggered.

The first snippet uses a QueryString:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    If (Request.QueryString("status") = "success") Then
        ScriptManager.RegisterStartupScript(Page, Page.GetType, "ShowInfoPage", "ShowInfoPage(1)", true)
    End If        
End Sub

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
    Response.Redirect(Request.RawUrl.ToString() + "?status=success", false);
End Sub

If you do not want a QueryString parameter to be visible you can use a Session:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)       
    If (Not (Session("status")) Is Nothing) Then
        If (Session("status").ToString = "success") Then
            ScriptManager.RegisterStartupScript(Page, Page.GetType, "ShowInfoPage", "ShowInfoPage(2)", true)
            Session.Remove("status")
        End If            
    End If        
End Sub

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
    Session("status") = "success"
    Response.Redirect(Request.RawUrl.ToString, false)
End Sub

I used this code translator, so the VB code may not be 100% accurate.

You cannot prevent re-submitting the form when the user presses F5 or refreshes the page by default. This is just inherent behavior of browsing the internet. If this continues to be a problem you should maybe look into an Ajax solution?