Check if unassigned variable exists in Request.QueryString

Question

Within the context of an ASP.NET page, I can use Request.QueryString to get a collection of the key/value pairs in the query string portion of the URI.

For example, if I

Answer 1

Request.QueryString is a NameValueCollection, but items are only added to it if the query string is in the usual [name=value]* format. If not, it is empty.

If your QueryString was of the form ?test=value, then Request.QueryString.AllKeys.Contains("test") would do what you want. Otherwise, you're stuck doing string operations on Request.Url.Query.