How to Access web service method Asynchronously ?

Question

I am consuming a web service. I wanna call its method asynchronously.

I called method asynchronouly but results are not returned.

I call the method like:

search.BeginGetData("DEMO", 1, 1, 0, 200000, 1, New AsyncCallback(AddressOf Responder), search)

My method is:

Private Sub Responder(ByVal Result As IAsyncResult)
    Dim s As PropertySearch = Result.AsyncState

    Dim dset As DataSet = DirectCast(s.EndGetData(Result), DataSet)

    GridView1.DataSource = dset.Tables("properties")
    GridView1.DataBind()
    Me.Label1.Text = dset.Tables("properties").Rows(0)(0).ToString()
End Sub

Please let me know what is wrong with my code.