Home » ASP.NET » ASP.NET Response.Redirect() and JavaScript

ASP.NET Response.Redirect() and JavaScript

A toucan perched on a branch in Brazil. Yesterday we covered issues surrounding using ASP.NET’s Response.Redirect in server side code. We noted that not handing it correctly could prevent code from running on the server that we want to run.

The other issue is emitting Javascript in the server side in association with Response.Redirect(). This also leads to unexpected problems if you aren’t thinking about what is actually happening with your code.

Take this code as an example:

    protected void Page_Load(object sender, EventArgs e)
        string myscript = @"<script language='javascript'>
alert('hello world');
            ("".GetType(), "s", myscript);


The question is, why does the javascript never display “hello world”?

Actually, the javascript is typically a little more complicated than “hello world.” But the question is always, “Why didn’t my javascript execute? It works fine without the redirect.”

Once again, we need to think more clearly about what we’ve actually written.

What we’ve actually told the server to do is the following:

  1. Render the javascript to display “hello world” in an alert box on the client.
  2. Set the header (not the header element, but the header that tells the browser whether the code executed successfully or not) to “302 redirect.”

When the browser finally gets the stream back from the server, it will actually see step 2 first because the header comes before the javascript code. The browser will look at that 302, ignore everything else on the page, and faithfully redirect to the page specified as part of the 302.


Other post in ASP.NET

Related Post

  • Response.Redirect() executes too soon on the Server.Response.Redirect() executes too soon on the Server. I've seen this question a couple of times in various situations. The first involves Javascript and the second involves server side code. Both are caused by a misunderstanding of what this […]
  • Infinite 302 Loop – How would you even know?Infinite 302 Loop – How would you even know? It happens eventually to all web developers.  It's happened to me twice in the last week.  You make one simple change to your web site and then you can no longer access it.  When you […]
  • ASP.NET Cross Domain Form SubmissionASP.NET Cross Domain Form Submission Not to be confused with cross page posting, cross domain submission allows us to post the contents of an ASP.NET form to a completely different domain. To achieve this we will need to […]
  • WebForms vs MVC–The War Is OverWebForms vs MVC–The War Is Over loading... I just finished listening to a DotNetRocks podcast today with Paul Sheriff which largely talked about creating mobile web sites using ASP.NET WebForms. During the show they […]
  • ASP.NET JSON  and ViewStateASP.NET JSON and ViewState I received the following question recently about my article "ASP.NET AJAX using JSON - Here’s how." If we update the value of a textbox or label via a JSON web service call - will the […]

About Dave Bush

Dave Bush is a Full Stack ASP.NET developer focusing on ASP.NET, C#, Node.js, JavaScript, HTML, CSS, BootStrap, and Angular.JS.Does your team need additional help in any of the above? Contact Dave today.

  • Noor

    how to prevent this and follow the initial plan described in above steps.

  • Dave

    Use a javascript redirect after the javascript you want to see run:

    window.location = “urlToRedirectTo”;