Prevent redirect on web form error

Prevent redirect on web form error

I'm working on a site written in asp.net, I have a form bounded to a
sqldatasource. Happens that when errors occur during form submission, the
user is redirected to the error page. What I want to obtain is to show the
error on the same page, or in an alert, remaining in the same page.
I do not need to know how to show an alert or how to append code to a
page, I just want to find a way to stop the page from redirecting.
I need something like "preventDefault ()" in javascript, to have something
like:
Protected Sub Page_Error(ByVal sender As Object, ByVal e As
System.EventArgs) Handles Me.Error
Dim ex As Exception = Server.GetLastError()
//Report exception to user
...
//Then prevent someway page from redirect
preventDefault() //Need something similar
//or
Return false //Need something similar
End Sub
NOTE I already knew try/catch method , I'm seeking a way to block the page
in case of unhandled errors.