System.NullReferenceException passing var to web service proxy class

[Ted]

Would someone tell me why I am getting:

"An unhandled exception of type 'System.NullReferenceException' occurred in
microsoft.visualbasic.dll. Additional information: Object variable or With
block variable not set" on this line of code:

lbitemSel = ws.GetImageFile(ListBox1.SelectedItem.GetType.ToSt ring())

My client code with correct Syntax is:

Dim ws As New GetImageApp.localhost.Service1, dimeAttachment As
Microsoft.Web.Services.Dime.DimeAttachment, lbitem As String

lbitemSel = ws.GetImageFile(ListBox1.SelectedItem.ToString())

When I try it this way I get a syntax error: "Too many arguments to Public
Function ws.GetImageFile()" when I try it in this way:

Dim lbitemSel As String

lbitemSel = ListBox1.SelectedItem.ToString()

ws.GetImageFile(lbitemSel)

My Web Service object is WS with strLbItemSel declared as a string:

Public Function GetImageFile(ByVal lbItemSel As String)

thx,

Ted