I have created a web service that access a database and retrieves record
then returns them as a dataset. I am having a problem coding a client
application to use the dataset. Here is the relevent code:
Web Service Code:

Public Function Query(ByVal computername As String) As DataSet
   Dim conStr As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" +
Server.MapPath("inv.mdb")
   Dim sqlStr As String
   sqlStr = "SELECT * FROM inv WHERE Decal = '" & computername & "';"
   Dim myConnection As New OleDbConnection(conStr)
   Dim myCommand As New OleDbCommand(sqlStr, myConnection)
   myConnection.Open()
   Dim myDataAdapter As New OleDbDataAdapter
   myDataAdapter.SelectCommand = myCommand
   Dim myDataSet As New DataSet
   myDataAdapter.Fill(myDataSet)
   myConnection.Close()
   Return myDataSet
End Function

Client Code:

Private Sub btnQuery_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
   Dim computername As String
   computername = TextBox1.Text
   Dim ws As New invweb.Inventory_Database_Query
   Dim querydata As DataSet
   querydata.Merge(ws.Query(computername))
End Sub

This generates a
System.NullReferenceException
it says:
Object reference not set to an instance of an object.
on
querydata.Merge(ws.Query(computername))

any suggestion on how to get this to work.

Thanks in advance

David York