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.GetValues(null) will get a list of keys with no values

Request.QueryString.GetValues(null).Contains("test") will return true