Outputting a manipulated QueryString in C#
HttpValueCollection is internal, but you can use "var" to declare it without extract it with reflector.
var query = HttpUtility.ParseQueryString(Request.Url.Query);query["Lang"] = myLanguage; // Add or replace paramstring myNewUrl = Request.Url.AbsolutePath + "?" + query;
You can also use Reflector to extract the HttpValueCollection class into your own, and use it then.
Because it is actually a special NVC that is of type HTTPValueCollection.So when you call .ToString on it, it knows how to format it correctly.