Visual Basic Solution

Request.QueryString.GetValues(vbNullString).Contains("test")

Although @Joe's answer is the correct answer, it doesn't account for VB.net programmers. The VB issue with @Joe's [correct] answer is that it yields an error at the "GetValues(null)" section. vbNullString alleviates the issue.

Additional Note

ClientQueryString.Contains("test")

might solve your problem (it did for me). Please know, though, that this solution has its pitfalls.

Summary for VB Programmers

Either of these will [probably] get the job done for you:

1. Request.QueryString.GetValues(vbNullString).Contains("test")
2. ClientQueryString.Contains("test")

I would've added this as a comment, but I don't have enough reputation points (43 out of 50)