asp.net source code blog

You may often use the Response's Redirect method to open new pages, ex:

Response.Redirect("http://www.devtheweb.net");

It will open the url in the same window.

If you want to open url by server side in a new window, it cannot be done using the Response's Redirect method.
But it can be done using JavaScript, here is an example:

ClientScript.RegisterStartupScript(typeof(Page), "key", "<script>window.open('http://www.devtheweb.net','_blank')</script>");