Q:

ASP.NET Response.Redirect( ) Error

Here is my code:
try
{
    Session["CuponeNO"] = txtCode.Text;
    txtCode.Text = string.Empty;
    Response.Redirect("~/Membership/UserRegistration.aspx");
}
catch(Exception ex)
{
   string s = ex.ToString();
   lblMessage1.Text = "Error Occured!";
}

I am getting an error, even though it redirects after catch.
Here is the error:

"System.Threading.ThreadAbortException:
  Thread was being aborted.\r\n   at
  System.Threading.Thread.AbortInternal()\r\n
  at
  System.Threading.Thread.Abort(Object
  stateInfo)\r\n   at
  System.Web.HttpResponse.End()\r\n   at
  System.Web.HttpResponse.Redirect(String
  url, Boolean endResponse)\r\n   at
  System.Web.HttpResponse.Redirect(String
  url)\r\n

Can anyone tell me why this error is occurring?

A:

You could simply move ....
Response.Redirect("~/Membership/UserRegistration.aspx");

... outside of the Try / Catch block or you can try John S. Reid's newer solution below :

Response.Redirect(url) ThreadAbortException Solution
by John S. ReidMarch 31, 2004(edited October 28, 2006 to include greater detail and fix some inaccuracies in my analysis, though the solution at it's core remains the same)

... skipping down ...

The ThreadAbortException is thrown when you make a call to Response.Redirect(url) because the system aborts processing of the current web page thread after it sends the redirect to the response stream. Response.Redirect(url) actually makes a call to Response.End() internally, and it's Response.End() that calls Thread.Abort() which bubbles up the stack to end the thread. Under rare circumstances the call to Response.End() actually doesn't call Thread.Abort(), but instead calls HttpApplication.CompleteRequest(). (See this Microsoft Support article for details and a hint at the solution.)

... skipping down ...

PostBack and Render Solutions? Overrides.
The idea is to create a class level variable that flags if the Page should terminate and then check the variable prior to processing your events or rendering your page. This flag should be set after the call to HttpApplication.CompleteRequest(). You can place the check for this value in every PostBack event or rendering block but that can be tedious and prone to errors, so I would recommend just overriding the RaisePostBackEvent and Render methods as in the code sample1 below:
private bool m_bIsTerminating = false;

protected void Page_Load(object sender, EventArgs e)
{
    if (WeNeedToRedirect == true)
    {
        Response.Redirect(url, false);
        HttpContext.Current.ApplicationInstance.CompleteRequest();
        m_bIsTerminating = true;

        // Remember to end the method here if there is more code in it.
        return;
    }
}

protected override void RaisePostBackEvent
(
    IPostBackEventHandler sourceControl, 
    string eventArgument
)
{
    if (m_bIsTerminating == false)
    base.RaisePostBackEvent(sourceControl, eventArgument);
}

protected override void Render(HtmlTextWriter writer)
{
    if (m_bIsTerminating == false)
    base.Render(writer);
}

The Final Analysis
Initially I had recommended that you should simply replace all of your calls to Response.Redirect(url) with the Response.Redirect(url, false) and CompleteRequest() calls, but if you want to avoid postback processing and html rendering you'll need to add the overrides as well. From my recent in depth analysis of the code I can see that the most efficient way to redirect and end processing is to use the Response.Redirect(url) method and let the thread be aborted all the way up the stack, but if this exception is causing you grief as it does in many circumstances then the solution here is the next best thing.
It should also be noted that the Server.Transfer() method suffers from the same issue since it calls Response.End() internally. The good news is that it can be solved in the same way by using the solution above and replacing the call to Response.Redirect() with Server.Execute().

1 - I modified the code formatting to make it fit inside SO boundaries so it wouldn't scroll.

