Hello all,
I have a web service that I am trying to retrieve data from
asynchronously. According to the MSDN documentation
(ms-help://MS.VSCC.2003/MS.MSDNQTR.2003FEB.1033/vbcon/html/vbtskCallingWebServiceAsynchronously.htm)
I should be able to call a webservice asynchronously using a delegate
function. The callback seems to work, but, when I assign the value to an
existing datagrid the program hangs. I don't quite understand, what do I
need to do?

TIA,
Jared

'Webservice call
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim cb As New AsyncCallback(AddressOf MyCallback)
myservice.BeginDoSomeAsyncStuff(cb, myservice)
End Sub

'Callback delegate
Private Sub MyCallback(ByVal ar As System.IAsyncResult)
Dim myservice As MCAD_Practice.MyService = ar.AsyncState
ds = myservice.EndDoSomeAsyncStuff(ar)
Me.DataGrid1.DataSource = ds.tables(0)
me.DataGrid1.Expand(True)
End Sub

'Web method - work just fine if I call it synchronously
<WebMethod()> _
Function DoSomeAsyncStuff() As DataSet
Dim conn As SqlConnection
Try
conn = New
SqlConnection("Server=localhost;database=northwind;trusted_connection=true;")
conn.Open()
Dim da As New SqlDataAdapter("Select * from customers order by
CompanyName", conn)
Dim ds As New DataSet("NorthwindCustomers")
da.Fill(ds)
Return ds
Catch ex As Exception
Finally
conn.Close()
End Try
End Function

Hi,

A couple of msdn tv episodes about it.

http://msdn.microsoft.com/msdntv/epi...B/manifest.xml

http://msdn.microsoft.com/msdntv/epi...B/manifest.xml

Ken
---------------------
"Jared" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
Hello all,
I have a web service that I am trying to retrieve data from
asynchronously. According to the MSDN documentation
(ms-help://MS.VSCC.2003/MS.MSDNQTR.2003FEB.1033/vbcon/html/vbtskCallingWebServiceAsynchronously.htm)
I should be able to call a webservice asynchronously using a delegate
function. The callback seems to work, but, when I assign the value to an
existing datagrid the program hangs. I don't quite understand, what do I
need to do?

TIA,
Jared

'Webservice call
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim cb As New AsyncCallback(AddressOf MyCallback)
myservice.BeginDoSomeAsyncStuff(cb, myservice)
End Sub

'Callback delegate
Private Sub MyCallback(ByVal ar As System.IAsyncResult)
Dim myservice As MCAD_Practice.MyService = ar.AsyncState
ds = myservice.EndDoSomeAsyncStuff(ar)
Me.DataGrid1.DataSource = ds.tables(0)
me.DataGrid1.Expand(True)
End Sub

'Web method - work just fine if I call it synchronously
<WebMethod()> _
Function DoSomeAsyncStuff() As DataSet
Dim conn As SqlConnection
Try
conn = New
SqlConnection("Server=localhost;database=northwind;trusted_connection=true;")
conn.Open()
Dim da As New SqlDataAdapter("Select * from customers order by
CompanyName", conn)
Dim ds As New DataSet("NorthwindCustomers")
da.Fill(ds)
Return ds
Catch ex As Exception
Finally
conn.Close()
End Try
End Function

Ken,
That was the kicker, I completely overlooked the fact that the web
service was being called from a seperate thread. Thanks,
Jared

Here is my working example if anyone else was following this thread.

Delegate Sub UpdateDataGrid(ByVal ds As DataSet)

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim cb As New AsyncCallback(AddressOf MyCallback)
myservice.BeginDoSomeAsyncStuff(cb, myservice)
End Sub

Private Sub MyCallback(ByVal ar As System.IAsyncResult)
Dim myservice As MyWebService.MyService = ar.AsyncState
Dim data As DataSet = myservice.EndDoSomeAsyncStuff(ar)
'Delegate
Dim grid As New UpdateDataGrid(AddressOf Bind)
Me.Invoke(grid, New Object() {Data})
End Sub

Private Sub Bind(ByVal ds As DataSet)
Me.DataGrid1.DataSource = ds.Tables(0)
Me.DataGrid1.Expand(True)
End Sub

"Ken Tucker [MVP]" <(E-Mail Removed)> wrote in message
news:%(E-Mail Removed)...
> Hi,
>
> A couple of msdn tv episodes about it.
>
> http://msdn.microsoft.com/msdntv/epi...B/manifest.xml
>
> http://msdn.microsoft.com/msdntv/epi...B/manifest.xml
>
> Ken
> ---------------------
> "Jared" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
> Hello all,
> I have a web service that I am trying to retrieve data from
> asynchronously. According to the MSDN documentation
> (ms-help://MS.VSCC.2003/MS.MSDNQTR.2003FEB.1033/vbcon/html/vbtskCallingWebServiceAsynchronously.htm)
> I should be able to call a webservice asynchronously using a delegate
> function. The callback seems to work, but, when I assign the value to an
> existing datagrid the program hangs. I don't quite understand, what do I
> need to do?
>
> TIA,
> Jared
>
> 'Webservice call
> Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles Button1.Click
> Dim cb As New AsyncCallback(AddressOf MyCallback)
> myservice.BeginDoSomeAsyncStuff(cb, myservice)
> End Sub
>
> 'Callback delegate
> Private Sub MyCallback(ByVal ar As System.IAsyncResult)
> Dim myservice As MCAD_Practice.MyService = ar.AsyncState
> ds = myservice.EndDoSomeAsyncStuff(ar)
> Me.DataGrid1.DataSource = ds.tables(0)
> me.DataGrid1.Expand(True)
> End Sub
>
> 'Web method - work just fine if I call it synchronously
> <WebMethod()> _
> Function DoSomeAsyncStuff() As DataSet
> Dim conn As SqlConnection
> Try
> conn = New
> SqlConnection("Server=localhost;database=northwind;trusted_connection=true;")
> conn.Open()
> Dim da As New SqlDataAdapter("Select * from customers order by
> CompanyName", conn)
> Dim ds As New DataSet("NorthwindCustomers")
> da.Fill(ds)
> Return ds
> Catch ex As Exception
> Finally
> conn.Close()
> End Try
> End Function
>
>
>