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When we start a workflow instance through a web service we might need to call it a second time. No big deal, all we need to do is add a second WebServiceInputActivity with a matching WebServiceOutputActivity to the workflow and we are good to go. However when we try to call the second method from our client we get the following error:
Server was unable to process request.
Current session has no workflow instance associated with it.
Well that is because the workflow engine adds a cookie named WF_WorkflowInstanceId to the response used to connect the second call to the same workflow. Alright the solution is simple; add the following to the web service before the first call:
workflows.CookieContainer = New CookieContainer()
Now everything works like a charm.
But suppose this is a long running workflow and we need to communicate with the same workflow a day later. We can hardly keep the proxy and cookie container in memory all this time. Well again the trick is simple, just save the details from the cookie, the Name, value, path and the domain and uses these to recreate the cookie next day.
Example client code:
Imports System.Net Module Module1 Private _cookieName As String Private _cookieValue As String Private _cookiePath As String Private _cookieDomain As String Sub Main() SubmitExpenses() GetStatus() Console.ReadLine() EndSub ''' <summary> ''' Day one, submit the expenses. ''' </summary> ''' <remarks></remarks> Private Sub SubmitExpenses() Dim workflows As New workflows.Workflow1_WebService workflows.CookieContainer = New CookieContainer() workflows.Submit("Holiday", 1000.0) ' Save the cookie info for next request Dim cookie As Cookie cookie = workflows.CookieContainer.GetCookies(New Uri(workflows.Url))(0) _cookieName = cookie.Name _cookiePath = cookie.Path _cookieValue = cookie.Value _cookieDomain = cookie.Domain EndSub ''' <summary> ''' Day two, come back and find its aproved :-) ''' </summary> ''' <remarks></remarks> Private Sub GetStatus() Dim workflows As workflows.Workflow1_WebService workflows = New workflows.Workflow1_WebService workflows.CookieContainer = New CookieContainer() Dim cookie As New Cookie(_cookieName, _cookieValue, _cookiePath, _cookieDomain) workflows.CookieContainer.Add(cookie) Console.WriteLine(workflows.GetStatus()) End Sub End Module
Enables receiving data from a Web service in a workflow.
23-11-2009 15:31:26 - -188.8.131.52
Enables sending data to a Web service from within a workflow.
23-11-2009 15:31:30 - -184.108.40.206
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23-11-2009 15:31:34 - anonymous