C# to VB .Net: Request.QueryString("$orderby")

Hi,
We are using server side binding for infragistics igGrid in our web application where following code of VB .Net do NOT work.
C#:
string orderby = Convert.ToString(HttpContext.Current.Request.QueryString["$orderby"]);
VB.NET:
Dim orderby As String = Convert.ToString(HttpContext.Current.Request.QueryString("$orderby
C#  code works fine in POC  but do NOT support for $orderby in VB.Net. I'm NOT knowing much about VB.Net. Please advise if Im missing something