Why do I get a thrown exception when I run Response.Redirect()?

Question

I am learning ASP.NET and was looking at QueryStrings.

One of the examples I was looking at hooks a button up to a redirect call:

    protected void btnSubmit_Click(object sender, EventArgs e)
    {
        try
        {
            //throws ThreadAbortException: "Thread was being aborted"
            Response.Redirect("Form2.aspx");
        }
        catch (Exception Ex)
        {
            System.Diagnostics.Debug.WriteLine(Ex.Message);
        }
    }

Why does it throw a ThreadAbortException here? Is that normal? Should I do something about this? Exceptions are generally not a good thing, so I was alarmed when I saw this.

Answer 1

This is by design. This KB article describes the behavior (also for the Request.End() and Server.Transfer() methods).

For Response.Redirect() there exists an overload:

Response.Redirect(String url, bool endResponse)

If you pass endResponse=false, then the exception is not thrown (but the runtime will continue processing the current request).

If endResponse=true (or if you use the overload without the bool argument), the exception is thrown and the current request will immediately be terminated.

Answer 2

This is normal. Server.Transfer() also throws the same exception.

This is because internally, both methods call Response.End(), which aborts the current request processing immediately. Rick Strahl has a pretty good blog post that analyzes why there is pretty much nothing you can do to avoid these exceptions.

Answer 3

Response.Redirect calls Response.End internally, so it throws the exception, use instead :

Response.Redirect(url, false);