Question

am trying to get the parameter “id” from the query string of the requested page like this

If Request.QueryString IsNot Nothing AndAlso _
            Request.QueryString.GetKey("id") IsNot Nothing Then
            DeleteVehicle(Request.QueryString.GetKey("id"))
 End If

but i get this error

System.NullReferenceException: Object reference not set to an instance of an object.

Source Error: 

Line 16:         If Request.QueryString IsNot Nothing AndAlso _
Line 17:             Request.QueryString.GetKey("id") IsNot Nothing Then

Source File: G:\projects_backup\Toaab\Toaa\admin\vehicle\view.aspx.vb    Line: 16 

please can you help me

EDIT

Am calling this in the page_load event

the same page (which has autogenerated link) is called through a hyperlink

i also change the code to

If Request.QueryString("id") IsNot Nothing OrElse Request.QueryString("id") IsNot String.Empty Then
 DeleteVehicle(Request.QueryString("id").ToString)
End If

Answer 1

To see if a value exists in the QueryString, check to see whether the value equates to an empty string rather than null:

Try this instead:

If String.IsNullOrEmpty(Request.QueryString("id")) = False Then
    DeleteVehicle(Request.QueryString("id"))
End If