Displaying results of an SPLongOperation - sharepoint

Question

I am using SPLongOperation to run a lengthy operation. After completing, the gears page redirects back to the original page from which the long operation was launched. I am not able to write anything to the oriignal page using SPLongOperation.Endscript. Here is the code I am using
using (SPLongOperation operation = new SPLongOperation(this.Page))
{
//.......................
//.......................
StringBuilder endScript = new StringBuilder();
endScript.Append("document.write('Success!!');");
operation.End(Request.Url.ToString(), SPRedirectFlags.UseSource, HttpContext.Current, String.Empty, endScript.ToString());
}

Answer 1

You won't be able to write anything to the calling page, a new http request has been made to show you the page with the spinning wheel while your operation is under progress and then you're redirected back to the specified url (using a new request).
The easiest way to show a success message is to pass a specific querystring to your calling url by replacing your string.empty parameter with something like
operation.End(Request.Url.ToString(), SPRedirectFlags.UseSource, HttpContext.Current, "success=1");
http://msdn.microsoft.com/en-us/library/ms450341.aspx
and then on the load event, check if you have this parameter and display the relevant message (it would be better to add an item to the HttpContext.Items or doing a post instead of a get to remove the querystring but the suggested implementation will prevent you from changing your long operation call and behaviour)
Hope this will help.

Answer 2

Try an alert - that worked for me..
Script.Append("alert('Success!!');");

Answer 3

This might be of help: http://www.sharepoint-tips.com/2012/07/reporting-code-errors-when-running-code.html
SPLongOperation longOp = new SPLongOperation(this.Page);
StringBuilder sbErrors = new StringBuilder();
longOp.Begin();try
{
throw new Exception("Sample");
}
catch(Exception ex)
{
sbErrors.Append("An error occurred: " + ex.MEssage);
}
if
(sbErrors.Length > 0)
{
longOp.EndScript("document.getElementById('s4-simple-card-content').innerHTML = \"Errors have occurred during the submission. Details: " + sbErrors.ToString() + " \";");
}
//close the dialog if there were no errors
longOp.EndScript("window.frameElement.commitPopup();");