PartialPageRendering when used with the UpdatePanel is a great thing in general. One problem comes when you want to mess with the Response and call things like End which is required when you return want to return a file instead of the page you were on. An example of this is a GridView with a Download button below it. If you are not using the UpdatePanel then there is no problem and clicking the Download button will all you to download the file as expected. There are lots of posts on the web on how to do this so I won’t go into the code. However, it involves calling things like Response.Clear(), Response.ContentType, Response.AddHeader(), Response.End().
Now let’s assume you put the GridView in an UpdatePanel. All those Response calls noted above are things that the PartialPageRendering and UpdatePanel don’t know what to do with because they were expected something like the page that made the request. So we need to work around the issue. I found some solutions on the internet, but didn’t really find them very easy or straight forward. So, I came up with my own.
One solution is to put the Download button outside the UpdatePanel. This tends to work best, but is not always possible.
If you can’t do solution 1, then consider faking it. What I mean is move the Download button which in my case is implemented as a LinkButton outside the UpdatePanel and hide it using css. Then add a Hyperlink inside the UpdatePanel. Now, on your page load you can set the hyperlink to have the same postback url as the LinkButton that is outside the UpdatePanel. That way when you click the hyperlink inside the UpdatePanel you are effectively doing the same thing as if you clicked the hidden LinkButton that is outside the UpdatePanel. Fairly simple.
Here is the snippets of code to help you see what I am talking about.
Here is the HyperLink that is inside the UpdatePanel and is also the button that you will be clicking in the Browser.
<asp:HyperLink ID="btnExportToExcelClicker" runat="server" Text="Export all rows to Excel" />
Here is the LinkButton that is invisible to the user and is outside the UpdatePanel
<asp:LinkButton ID="btnExportToExcel" runat="server" onclick="btnExportToExcel_Click" Text="Export all rows to Excel" style="display:none;" />
Here is the code-behind. In my code btnExportToExcelClicker is the button that is in the UpdatePanel and btnExportToExcel is the button that is outside the UpdatePanel. You will actually be clicking btnExportToExcelClicker because btnExportToExcel is hidden.
protected void Page_Load(object sender, EventArgs e)
btnExportToExcelClicker.NavigateUrl = Page.ClientScript.GetPostBackClientHyperlink(btnExportToExcel, null);
This technique uses GetPostBackClientHperlink and can be expanded for other purposes and other controls. In some cases you may need to consider using GetPostBackEventReferences, though I haven’t tried it.