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

I use this.

if (Request.Params["test"] != null)
{
    //Is Set
}
else if(Request.QueryString.GetValues(null) != null && 
       Array.IndexOf(Request.QueryString.GetValues(null),"test") > -1)
{
    //Not set
}
else
{
    //Does not exist
}