Question

I have a ASP.NET website where a user gets large data from a DB by clicking a button, but some times the user want to cancel the job(these jobs can take a very long time) and their session will hang while doing this job.

Is there any way to stop the execution of code and clean the already collected data ?

Is the best solution to have a table with all the jobIDs where a bit will determine if the code can continue and let the user change this from a button/link.

Answer 1

You may consider using AJAX and abort the current Request if the user hits a cancel button.

    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <script type="text/javascript" language="javascript">
        var sm = Sys.WebForms.PageRequestManager.getInstance();
        sm.add_initializeRequest(initRequest);

        function initRequest(sender, args) {
            if (sm.get_isInAsyncPostBack() && 
                args.get_postBackElement().id == 'btnStart') {

                args.set_cancel(true);  
                alert('Still progressing!\nPlease wait ...');
            } else if (sm.get_isInAsyncPostBack() && 
                       args.get_postBackElement().id == 'btnCancel') {
                sm.abortPostBack();
            }
        }

    </script>
    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>
            <asp:UpdateProgress ID="UpdateProgress1" runat="server">
                <ProgressTemplate>
                    <p>Processing....</p>
                   <asp:LinkButton ID="btnCancel" runat="server">Cancel</asp:LinkButton>
                </ProgressTemplate>
            </asp:UpdateProgress>
            <asp:LinkButton ID="btnStart" runat="server" onclick="btnStart_Click">Start work!</asp:LinkButton>
        </ContentTemplate>
    </asp:UpdatePanel>

Just put the database query in the corresponding serverside eventHandler

public partial class asyncLongLasting : System.Web.UI.Page
{
   protected void btnStart_Click(object sender, EventArgs e)
   {
       // your database query may start here
       System.Threading.Thread.Sleep(5000);
   }
}