[2008] Trying to call a method asyncronously

[Metallicaman]

im making a transport agent for exchange and am getting hung up on how to call a method asyncronously. Im doing this based on an msdn article but like usual they didnt provide the part of the code i need to figure out.

the article is in C# but i converted it to vb in my project.
http://msdn.microsoft.com/en-us/library/cc720860.aspx

I know I need to setup a delegate for the method and then invoke that delegate, but im not 100% on how to implement this.

Here is the code. AsyncDBCallback is the method i am trying to call. Any help would be appreciated.

Imports Microsoft.Exchange.Data.Transport.Routing
Imports Microsoft.Exchange.Data.Transport

Namespace TestTransportAgent
    NotInheritable Class TestAgentFactory
        Inherits RoutingAgentFactory

        Public Overrides Function CreateAgent(ByVal server As Microsoft.Exchange.Data.Transport.SmtpServer) As Microsoft.Exchange.Data.Transport.Routing.RoutingAgent
            Return New MyTestAgent
        End Function
    End Class

    Public Class MyTestAgent
        Inherits RoutingAgent

        Private Sub SubmittedMessageHandler(ByVal source As SubmittedMessageEventSource, ByVal e As QueuedMessageEventArgs) Handles Me.OnSubmittedMessage
            Dim asyncState As New AsyncState(Of SubmittedMessageEventSource, QueuedMessageEventArgs)(source, e, Me.GetAgentAsyncContext())
            Dim caller As New DelCallBackFunction(AddressOf AsyncDBCallback)
            'not sure how to implement it from thsi point
Dim result As IAsyncResult = caller.BeginInvoke(
        End Sub

        Delegate Sub DelCallBackFunction(ByVal ar As IAsyncResult)

        Private Sub AsyncDBCallback(ByVal ar As IAsyncResult)
            Dim asyncState As AsyncState(Of SubmittedMessageEventSource, QueuedMessageEventArgs) = DirectCast(ar.AsyncState, AsyncState(Of SubmittedMessageEventSource, QueuedMessageEventArgs))

            'Check message and send to web service
            If asyncState.Args.MailItem.Recipients.Contains("[email protected]") And asyncState.Args.MailItem.Message.Subject.Contains("chicken") Then
                Dim testt As webservice.Service = New webservice.Service
                Dim msg As String = asyncState.Args.MailItem.Message.Body.ToString

                Try
                    testt.HelloWorld(msg)
                Catch ex As Exception
                    Throw New Exception(Err.Description & " " & ex.Message)
                End Try
            ElseIf asyncState.Args.MailItem.Recipients.Contains("[email protected]") Then
                Dim testt As webservice.Service = New webservice.Service
                testt.HelloWorld("secondstatement")
            End If

            asyncState.Complete()
        End Sub

        Private Class AsyncState(Of SourceType, ArgsType)
            Private m_source As SourceType
            Private m_args As ArgsType
            Private asyncContext As AgentAsyncContext

            Public Sub New(ByVal source As SourceType, ByVal args As ArgsType, ByVal asyncContext As AgentAsyncContext)
                Me.m_source = source
                Me.m_args = args
                Me.asyncContext = asyncContext
            End Sub

            Public ReadOnly Property Source() As SourceType
                Get
                    Return Me.m_source
                End Get
            End Property

            Public ReadOnly Property Args() As ArgsType
                Get
                    Return Me.m_args
                End Get
            End Property

            Public Sub Complete()
                Me.asyncContext.Complete()

                Me.m_source = Nothing
                Me.m_args = Nothing
                Me.asyncContext = Nothing
            End Sub
        End Class
    End Class
End Namespace

[chris128]

Well to setup a delegate you simply do this (in this example we will pretend the method you are invoking just takes one string as an argument):

Delegate Sub MyDelegate(Byval SomeString As String)

And to invoke it you just do this:

Private Sub SomeExampleSub
    Invoke(New SomeDelegate(AddressOf TheSubIWantToRun), TheStringIWantToPassIn)
End Sub

Where "TheSubIWantToRun" would be the name of the sub that you actually want to pass this string to and the sub that will do whatever it is you are trying to 'invoke'

Hope that helps

[Metallicaman]

Im getting "overload resolution failed because no 'Invoke' is accessible" on the invoke part of the code.

Invoke(New DelCallBackFunction(AddressOf AsyncDBCallback), asyncState)
        End Sub

Delegate Sub DelCallBackFunction(ByVal ar As IAsyncResult)

[chris128]

Can you post a bit more the code around the bit you just posted so we can see exactly where you are using it?

[Metallicaman]

Hope this helps. Also in the msdn link they you might be able to get a gist of whats going on by reading the comments they have, to bad its in c# and they didnt provide a vb.net version

http://msdn.microsoft.com/en-us/library/cc720860.aspx

Private Sub SubmittedMessageHandler(ByVal source As SubmittedMessageEventSource, ByVal e As QueuedMessageEventArgs) Handles Me.OnSubmittedMessage
            Dim asyncState As New AsyncState(Of SubmittedMessageEventSource, QueuedMessageEventArgs)(source, e, Me.GetAgentAsyncContext())
            Invoke(New DelCallBackFunction(AddressOf AsyncDBCallback), asyncState)
End Sub

Delegate Sub DelCallBackFunction(ByVal ar As IAsyncResult)

Private Sub AsyncDBCallback(ByVal ar As IAsyncResult)
'code that does stuff
End Sub

Private Class AsyncState(Of SourceType, ArgsType)
            Private m_source As SourceType
            Private m_args As ArgsType
            Private asyncContext As AgentAsyncContext
            'public properties for each of the above variable
End Class

[chris128]

Well that code you just posted is different to the section you posted in your last post lol

The invoke line in this code is not passing in the IAsyncResult object that is required by the delegate you are trying to invoke.

[Metallicaman]

whoops my bad.

updated the code, I was messing around with guess I didnt change all the code back.

edit - also in the MSDN article this comment is what im having trouble implementing. That comment is place in the SubmittedMessageHandler right where that invoke code I put is.

// Call an asynchronous I/O method.
// Pass in this.AsyncIOCallback as the callback and
// asyncState as the state argument.

[Atheist]

The class you're inheriting (RoutingAgent) doesnt seem to expose an Invoke method, so you wont be able to call it like that. However delegates have Invoke methods:

Dim caller As New DelCallBackFunction(AddressOf AsyncDBCallback)
caller.Invoke(asyncState)

[Metallicaman]

Ok lemme give that a try

[chris128]

Ohh I didnt realise Invoke was a method, I thought it was just a command/keyword (like Dim and New etc)... I guess just because it is normally always available because I'm used to always attempting to use it from within a form class. Although the fact its not shown in the same way in intellisense should have given me a clue... but what can I say. Learn something everyday