Web Service and Threads

[wbarr@tin-man.co.uk]

What I'm trying to do is call a web service which then invokes a worker
thread. This thread should then handle any further lengthy processsing
freeing up the WebService to complete and terminiate.

To do this I'm using code similar

In the Client application I call

Public Sub InvokeWebService
Dim WS As New WS.Xfer

Try
Console.Write("Started")
Dim cb As AsyncCallback = New AsyncCallback(AddressOf MyCallback)
Dim ar As IAsyncResult = WS.BeginXfer(LogInf, cb, Nothing)
Catch e As Exception
Console.WriteLine("Exception Occured: " & e.ToString())
End Try
End Sub

Public Sub MyCallback(ByVal ar As IAsyncResult)
Dim WS As WS.Xfer = DirectCast(ar.AsyncState, WS.Xfer)
Dim ReturnValue As String = WS.EndXfer(ar)
Console.Write("Finished")
End Sub

Then in the web service I have the following

<WebMethod(Description:="Do Lengthy Processing.")> _
Public Function Xfer(ByVal newLogInfo As LogInfo) As Boolean
Return DoSomething(newLogInfo)
End Function

Private Function DoSomething(ByVal LogInfo As LogInfo) As Boolean
Dim st As New ThrdState
st.mLogInfo = LogInfo

...

ThreadPool.QueueUserWorkItem(New WaitCallback(AddressOf MyRefresh),
st)

...

Return True
End Function

' CALLBACK
Private Sub MyRefresh(ByVal state As Object)
Dim st As ThrdState = CType(state, ThrdState)
Dim LogInfo As LogInfo = st.mLogInfo

...
Do lengthy Processing here
...
End Sub

The problem is that when the web service completes the spawned thread
terminiates. What I want is for the Web Service to complete and the
spawned thread continue processing in the background. The Web Service
doesn't care what now happens in the spawned thread.

Any help greatly appreciated

[Brock Allen]

You should look into making your WebService an Async Handler:

[url]http://msdn.microsoft.com/msdnmag/issues/03/06/Threading/default.aspx[/url]

-Brock
DevelopMentor
[url]http://staff.develop.com/ballen[/url]

> What I'm trying to do is call a web service which then invokes a
> worker thread. This thread should then handle any further lengthy
> processsing freeing up the WebService to complete and terminiate.
>
> To do this I'm using code similar
>
> In the Client application I call
>
> Public Sub InvokeWebService
> Dim WS As New WS.Xfer
> Try
> Console.Write("Started")
> Dim cb As AsyncCallback = New AsyncCallback(AddressOf MyCallback)
> Dim ar As IAsyncResult = WS.BeginXfer(LogInf, cb, Nothing)
> Catch e As Exception
> Console.WriteLine("Exception Occured: " & e.ToString())
> End Try
> End Sub
> Public Sub MyCallback(ByVal ar As IAsyncResult)
> Dim WS As WS.Xfer = DirectCast(ar.AsyncState, WS.Xfer)
> Dim ReturnValue As String = WS.EndXfer(ar)
> Console.Write("Finished")
> End Sub
> Then in the web service I have the following
>
> <WebMethod(Description:="Do Lengthy Processing.")> _
> Public Function Xfer(ByVal newLogInfo As LogInfo) As Boolean
> Return DoSomething(newLogInfo)
> End Function
> Private Function DoSomething(ByVal LogInfo As LogInfo) As Boolean
> Dim st As New ThrdState
> st.mLogInfo = LogInfo
> ...
>
> ThreadPool.QueueUserWorkItem(New WaitCallback(AddressOf MyRefresh),
> st)
>
> ...
>
> Return True
> End Function
> ' CALLBACK
> Private Sub MyRefresh(ByVal state As Object)
> Dim st As ThrdState = CType(state, ThrdState)
> Dim LogInfo As LogInfo = st.mLogInfo
> ...
> Do lengthy Processing here
> ...
> End Sub
> The problem is that when the web service completes the spawned thread
> terminiates. What I want is for the Web Service to complete and the
> spawned thread continue processing in the background. The Web Service
> doesn't care what now happens in the spawned thread.
>
> Any help greatly appreciated
>