[RESOLVED] Asynchronous WCF Service

[RobGue]

Hello everybody!

I'm new to the WCF architecture and need some help in realizing an
asynchronous WCF Service.

Currently I just don't get it how to bring it working.


First of all this is how my main service contract is coded:

<ServiceContract()>
Public Interface IMainService
 
  <OperationContract(ProtectionLevel:=Net.Security.ProtectionLevel.None)>
  Function GetData(ByVal value As Integer) As String
 
  <OperationContract(AsyncPattern:=True)>
  Function BeginAdd(ByVal value1 As Integer, _
                    ByVal value2 As Integer, _
                    ByVal callback As AsyncCallback, _
                    ByVal state As Object) As IAsyncResult
 
  Function EndAdd(ByVal ar As IAsyncResult) As String
 
End Interface

Here is the implementation:

Public Class MainService
  Implements IMainService
 
  Public Sub New()
  End Sub
 
  Public Function GetData(ByVal value As Integer) As String _
                                                  Implements IMainService.GetData
 
    Return String.Format("You entered: {0}", value)
 
  End Function
 
  Public Function BeginAdd(ByVal value1 As Integer, ByVal value2 As Integer, _
                           ByVal callback As System.AsyncCallback, ByVal state As Object) As System.IAsyncResult _
                                                                                          Implements IMainService.BeginAdd
 
    Return New CompletedAsyncResult(Of Integer)(value1 + value2)
 
  End Function
 
  Public Function EndAdd(ByVal ar As System.IAsyncResult) As String _
                                                          Implements IMainService.EndAdd
    Dim result As CompletedAsyncResult(Of String) = TryCast(ar, CompletedAsyncResult(Of String))
    Return result.Data
 
  End Function
 
End Class
 
Friend Class CompletedAsyncResult(Of T)
  Implements IAsyncResult
 
  Private data_Renamed As T
 
  Public Sub New(ByVal data As T)
    Me.data_Renamed = data
  End Sub
 
  Public ReadOnly Property Data() As T
    Get
      Return data_Renamed
    End Get
  End Property
 
#Region "IAsyncResult Members"
  Public ReadOnly Property AsyncState() As Object Implements IAsyncResult.AsyncState
    Get
      Return CObj(data_Renamed)
    End Get
  End Property
 
  Public ReadOnly Property CompletedSynchronously() As Boolean Implements IAsyncResult.CompletedSynchronously
    Get
      Return True
    End Get
  End Property
 
  Public ReadOnly Property IsCompleted() As Boolean Implements IAsyncResult.IsCompleted
    Get
      Return True
    End Get
  End Property
 
  Public ReadOnly Property AsyncWaitHandle As System.Threading.WaitHandle Implements System.IAsyncResult.AsyncWaitHandle
    Get
      Throw New Exception("The method or operation is not implemented.")
    End Get
  End Property
#End Region
 
End Class

I'm familiar with the basics on using asynchronous operations "offline".
But I think I'm missing some links to the "online" usage of such operations.

Here is my client code:

Imports System.ServiceModel
 
Module MainModule
 
  Sub Main()
 
    Dim basicHttpBind As New BasicHttpBinding()
    Dim endpointAddress As New EndpointAddress("http://localhost:2053/MainService.svc")
    Dim mainService As IMainService = New ChannelFactory(Of IMainService)(basicHttpBind, endpointAddress).CreateChannel
 
    'Console.WriteLine(mainservice.GetData(123))
 
    Dim value1 As Integer = 100
    Dim value2 As Integer = 15
 
    Dim arAdd As IAsyncResult = mainService.BeginAdd(value1, value2, Nothing, mainService)
    Console.WriteLine("Add({0},{1})", value1, value2)
 
    While Not arAdd.IsCompleted
      Console.WriteLine("Waiting...")
      Threading.Thread.Sleep(1000)
    End While
 
    Console.WriteLine(mainService.EndAdd(arAdd))
 
    Console.ReadKey()
 
  End Sub
 
  Private Sub AddCallback(ByVal ar As IAsyncResult)
    Dim result = (CType(ar.AsyncState, IMainService)).EndAdd(ar)
    Console.WriteLine("Add Result: {0}", result)
  End Sub
 
End Module

The Callback isn't working.

So I would be really happy if someone could help me out.
On the net I did not find any useful hints for me.

It's important to me to understand the whole process in detail.

Kind regards
Robin

[Lightning]

I didn't run the code (no IDE at the moment, beside I prefer C#), but I see the AddCallback function is never called. I think it should by in this line:

Dim arAdd As IAsyncResult = mainService.BeginAdd(value1, value2, [B]AddCallback[/B], mainService

An other thing is the you neven want to wait for a async action in a loop. The whole point of async is the "not waiting"

[RobGue]

Hi Lightning!

Thanks for the hint.

Indeed I forget to use that callback


The next error was, that the Begin and End Functions weren't type safe.

I changed both to Integer.


Now it works all well :-)