Question

I only need to parse URL Request.Querystrings on GET, not on postback, right?

if(!IsPostBack)
{
    Viewstate["magic_number"] = Parse(Request.Query);
}

The user can’t be expected to modify the URL in the Request for subsequent postbacks, or can they?

Motivation for question– I don’t control the javascript snippet that does the postback, so it’s something of blackbox to me.

Answer 1

The URL is not expected to change. But remember that each postback is a new instance of your page class. So if you didn’t save the results somewhere on the first view you need to be prepared to do it again on the next one, and so on. In this case you saved it to ViewState, and so that should be fine.

However, I suspect you wouldn’t be asking the question unless you had observed behavior that led you to suspect otherwise. So let’s consider for a moment what things could cause this to break:

• It is possible to modify ViewState at the client where you saved your results (though not trivial and definitely not recommended).
• You can fake a postback before the initial page view.
• You can use javascript to alter the posted url.

However, for all these things you would certainly know if you have written anything to do that.