The Problem Solver : .NET

Rehosting the Workflow Designer in WF4

Maurice — Wed, 23 Dec 2009 16:46:22 GMT

Note: This blog post is written using the .NET framework 4.0 Beta 2

With Windows Workflow Foundation 3 it was possible to rehost the workflow designer in your own application. But possible is about all there was to say about it as it was pretty hard to do anything beyond the basics.

With Windows Workflow Foundation 4 live has become much better on the rehosting front In fact it is possible to create the fully functional and useful workflow editor below in about 200 lines of code. Now that is more like it!

The WorkflowDesigner

The WorkflowDesigner is the main class to work with. This exposes the actual design surface through the View property and the linked property sheet through the PropertyInspectorView property. Both these properties point to ready to use WPF UIElement’s so, as long as the host used WPF, adding them to a form is easy. And loading or saving a workflow is easy to, all it takes is a Load() and Save() function pointing to a XAML file. The code that does this part is below:

_workflowDesigner = new WorkflowDesigner();

_workflowDesigner.Load(_fileName);

var view = _workflowDesigner.View;

Grid.SetColumn(view, 1);

Grid.SetRow(view, 1);

LayoutGrid.Children.Add(view);

var propInspector = _workflowDesigner.PropertyInspectorView;

Grid.SetColumn(propInspector, 2);

Grid.SetRow(propInspector, 1);

LayoutGrid.Children.Add(propInspector);

DesignerMetadata

One thing that is needed is to register the workflow activity designer metadata. It is just a single call but leaving it out means all activities are just a small collapsed shape and won’t expand.

new DesignerMetadata().Register();

Displaying the toolbox with activities

The toolbox on the left if another standard WPF control called the ToolboxControl. Again easy to add to any WPF form. Add to it ToolboxItemWrapper with the activity type to add and you are good to go. Dragging controls onto the design surface just works, no extra work required. In the code below I just scan through all types in a few assemblies and if they are valid activities I add them to the toolbox. Again nice and easy.

var toolbox = new ToolboxControl();

var cat = new ToolboxCategory("Standard Activities");

var assemblies = new List<Assembly>();

assemblies.Add(typeof(Send).Assembly);

assemblies.Add(typeof(Delay).Assembly);

assemblies.Add(typeof(ReceiveAndSendReplyFactory).Assembly);

var query = from asm in assemblies

            from type in asm.GetTypes()

            where type.IsPublic &&

            !type.IsNested &&

            !type.IsAbstract &&

            !type.ContainsGenericParameters &&

            (typeof(Activity).IsAssignableFrom(type) ||

            typeof(IActivityTemplateFactory).IsAssignableFrom(type))

            orderby type.Name

            select new ToolboxItemWrapper(type);

query.ToList().ForEach(ti => cat.Add(ti));

toolbox.Categories.Add(cat);

Grid.SetColumn(toolbox, 0);

Grid.SetRow(toolbox, 1);

LayoutGrid.Children.Add(toolbox);

The current selection

At the top of the form I display the currently selected activity and its parents. The WorkflowDesigner has an Items collection with a bunch of useful objects in there. One of these is a Selection object. We could periodically check this Selection but its even easier to subscribe to chances using the Subscribe() function and passing in a handler that is called whenever the selection changes. Setting up the subscription is another one-liner.

_workflowDesigner.Context.Items.Subscribe<Selection>(SelectionChanged);

The handler itself isn’t very complex either.

private void SelectionChanged(Selection selection)

    var modelItem = selection.PrimarySelection;

    var sb = new StringBuilder();

    while (modelItem != null)

        var displayName = modelItem.Properties["DisplayName"];

        if (displayName != null)

            if (sb.Length > 0)

                sb.Insert(0, " - ");

            sb.Insert(0, displayName.ComputedValue);

        modelItem = modelItem.Parent;

    CurrentActivityName.Text = sb.ToString();

Validating the workflow

It would be nice to let the user know if the workflow is valid. Again quite easy to do by adding a IValidationErrorService to the WorkflowDesigner services collection. In this case I added a listbox to the form and let the IValidationErrorService add each error to the ListBox items. No need to call anything, the IValidationErrorService is automatically called as soon as anything in the workflow changes.

var validationErrorService = new ValidationErrorService(WorkflowErrors.Items);

_workflowDesigner.Context.Services.Publish<IValidationErrorService>(validationErrorService);

The IValidationErrorService consists of a single function that gets the list of errors as a parameter.

public class ValidationErrorService : IValidationErrorService

    private IList _errorList;

    public ValidationErrorService(IList errorList)

        _errorList = errorList;

    public void ShowValidationErrors(IList<ValidationErrorInfo> errors)

        _errorList.Clear();

        foreach (var error in errors)

            _errorList.Add(error.Message);

Running the workflow

Just to be able to run the workflow I added a bit of code that uses a WorkflowApplication to run the workflow. Loading it is also easy, just call the ActivityXamlServices.Load() passing in the file and it will return a DynamicActivity ready to run.

var writer = new StringWriter();

var workflow = ActivityXamlServices.Load(_fileName);

var wa = new WorkflowApplication(workflow);

wa.Extensions.Add(writer);

wa.Completed = WorkflowCompleted;

wa.OnUnhandledException = WorkflowUnhandledException;

wa.Run();

So all together I have a working application that I can use to edit and run workflows. So who still needs Visual Studio 2010?

Sweet

Download CustomWorkflowDesigner.zip

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Flowing transaction into a workflow using WF4

Maurice — Mon, 21 Dec 2009 16:43:44 GMT

Note: This blog post is written using the .NET framework 4.0 Beta 2

One of the things that wasn’t possible in Windows Workflow Foundation 3 was flowing transaction over a WCF service request into a workflow. We could have transactions on the client, we could have transactions on the server but they would not be able to cooperate.

Fortunately that is one the problems that Windows Workflow Foundation 4 solves for us.

In WF4 we can use the ReceiveAndSendreply template to configure a workflow as a service and accept WCF calls. That works just fine but doesn’t allow for transactions. If we want to use transactions we need to add the TransactedReceiveScope to the workflow. Move the ReceiveRequest activity into the Request part and the SendResponse activity into the Body part. Don’t forget the last part because leaving the SendResponse below the TransactedReceiveScope means things will not work and the error message will be less that helpful

This is enough to make all work done during the message receive part of a transaction. To show what is happening with transactions I am using the following code to record and return the transactional status:

using System.Text;

using System.Transactions;

public class TransactionReport

    public static string GetReport()

        var sb = new StringBuilder();

        if (Transaction.Current == null)

            sb.Append("No transaction");

        else

            sb.AppendFormat("TransactionInformation\n");

            sb.AppendFormat("\tLocalIdentifier {0}\n", Transaction.Current.TransactionInformation.LocalIdentifier);

            sb.AppendFormat("\tDistributedIdentifier {0}\n", Transaction.Current.TransactionInformation.DistributedIdentifier);

            sb.AppendFormat("\tStatus {0}\n", Transaction.Current.TransactionInformation.Status);

            sb.AppendFormat("\tIsolationLevel {0}\n", Transaction.Current.IsolationLevel);

        return sb.ToString();

Adding a console application with a service reference with the following code:

using System;

using Client.ServiceReference1;

namespace Client

    class Program

        static void Main(string[] args)

            var proxy = new ServiceClient();

            var result = proxy.PostData();

            Console.WriteLine(result);

            Console.ReadLine();

Produces the following output:

No big surprises there. The only thing I am missing is the ability to control the IsolationLevel which seems to be fixed at Serializable.

Flowing transactions from the client

The first step we need to take for client transactions to flow to the service is do the service call inside of a transaction using this client code:

using System;

using System.Transactions;

using Client.ServiceReference1;

namespace Client

    class Program

        static void Main(string[] args)

            using (var tx = new TransactionScope())

                Console.WriteLine(TransactionReport.GetReport());

                var proxy = new ServiceClient();

                var result = proxy.PostData();

                Console.WriteLine(result);

                Console.WriteLine(TransactionReport.GetReport());

            Console.ReadLine();

If we run the code now we get the following output:

The transaction is there on the client but DistributedIdentifier is still empty so the transaction doesn’t flow to the service yet.

Before transactions will flow we need to do two things. First of all we need a WCF binding that can flow transactions. So far we have been using the BasicHttpBinding, the default for an HTTP endpoint in the .NET 4 default configuration, which doesn’t support transactions. So we need to switch to something like WSHttpBinding that does. Next we need to enable transaction flow because it is disabled by default. All of this can be done by adding a little extra configuration to the web.config file.

<bindings>

  <wsHttpBinding>

    <binding transactionFlow="true"/>

  </wsHttpBinding>

</bindings>

<services>

  <service name="Service1">

    <endpoint address=""

              binding="wsHttpBinding"

              contract="IService" />

  </service>

</services>

With this in place all we need to do is update the client service reference and transactions will flow from the client to the service.

Keep in mind that flowing transactions across a network boundary is a very powerful but also a very dangerous concept. You might be letting someone else, from a different organization, place locks on your database. So make sure you understand the implications of flowing transactions before you open up a whole can of worms!

Nice

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Online WF4 presentation recordings

Maurice — Tue, 08 Dec 2009 11:57:03 GMT

The recordings from my recent online Windows Workflow Foundation 4 presentation have been posted online. Get them while they are hot

You can download the samples and PowerPoint from here.

Streaming:

http://developmentor.s3.amazonaws.com/webcasts/Meet-The-New-Workflow-WF4-Maurice-de-Beijer-2009-12-01.wvx

Video Download:

http://developmentor.s3.amazonaws.com/webcasts/Meet-The-New-Workflow-WF4-Maurice-de-Beijer-2009-12-01.zip

Video As WMV (used by streaming link):
http://developmentor.s3.amazonaws.com/webcasts/Meet-The-New-Workflow-WF4-Maurice-de-Beijer-2009-12-01.wmv

MP3 (iTunes Ready):
http://developmentor.s3.amazonaws.com/webcasts/Meet-The-New-Workflow-WF4-Maurice-de-Beijer-2009-12-01.mp3

Download MP3 (iTunes Ready):

http://developmentor.s3.amazonaws.com/webcasts/Meet-The-New-Workflow-WF4-Maurice-de-Beijer-2009-12-01-mp3only.zip

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Activity correlation using a RequestReplyCorrelationInitializer

Maurice — Thu, 03 Dec 2009 18:16:59 GMT

Note: This blog post is written using the .NET framework 4.0 Beta 2

In my previous post about Windows Workflow Foundation 4 I used the CorrelationScope activity to arrange for the activity correlation between a Send and the related ReceiveReply activities. That is quite easy to do and personally I find things nice and easy to arrange with both messaging activities nested in the CorrelationScope activity . The default templates use a slightly different approach though and use a RequestReplyCorrelationInitializer. The end result is the same though so just use what you think best.

Just for comparison below is the code to create the same workflow with a RequestReplyCorrelationInitializer.

static Activity CreateWorkflow()

    var getDataResult = new Variable<string>();

    var handel = new Variable<CorrelationHandle>();

    var send = new Send()

        CorrelationInitializers =

            new RequestReplyCorrelationInitializer()

                CorrelationHandle = handel

},

        OperationName = "GetData",

        ServiceContractName = "IService1",

        Endpoint = new Endpoint()

            Binding = new BasicHttpBinding(),

            AddressUri = new Uri("http://localhost:8080/GetDataService/")

},

        Content = new SendParametersContent()

            Parameters =

                {"value", new InArgument<int>(42)}

};

    var receive = new ReceiveReply()

        Request = send,

        Content = new ReceiveParametersContent

            Parameters =

                {"GetDataResult", new OutArgument<string>(getDataResult)}

};

    var workflow = new Sequence()

        Variables = { getDataResult, handel },

        Activities =

            send,

            receive,

            new WriteLine() { Text = getDataResult }

};

    return workflow;

The workflow is even a little simpler because there are fewer activities involved. And this is effectively the same as the SendAndReceiveReply and ReceiveAndSendReply templates generate in WF4.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Activity correlation in Windows Workflow Foundation 4

Maurice — Wed, 02 Dec 2009 17:57:49 GMT

Note: This blog post is written using the .NET framework 4.0 Beta 2

There are two types of correlation to think about in Windows Workflow Foundation:

Message correlation
Basically sending multiple requests to the same workflow.
Activity correlation
Making sure two activities work together.

In this post I am going to show activity correlation

Activity correlation is used when multiple activities form a single logical action. Think about the Send and ReceiveReply activities. Two distinct activities but they work together because the first, the Send activity, send a WCF request somewhere and the second, the ReceiveReply activity, receives the response. The same goes when receiving messages.

The good thing is that when we use the ReceiveAndSendReply or SendAndReceiveReply templates everything will be done for us and the required activity correlation will be configured automatically. However sometimes we might need to do so ourselves because we create a workflow in a different way, like using regular code.

So when we start using the Send and ReceiveReply or the Receive and SendReply activities from code we need to do a bit more work. How much varies and depends on both the workflow and the hosting environment we use. The big exception to the rule is when we use the WorkflowServiceHost and no parallel or overlapping messaging activities. In that case life is simple and the WorkflowServiceHost takes care of all required correlation for us. Nice

That does leave for quite a few scenarios where we do need to add activity correlation though. The obvious one is using the WorkflowApplication or WorkflowInvoker to run our workflows. Fortunately this produces an System.InvalidOperationException with a message like:

The Send activity is configured with a request/reply Operation 'GetData', however, there is no ReceiveReply activity paired with it. Please pair Send with ReceiveReply and correlate them using a CorrelationHandle.

There are different ways to configure activity correlation but the easiest way is to wrap the activity pair in a CorrelationScope activity. The CorrelationScope will automatically create the required correlation handle and the messaging activities will use this handle.

Show me the code

The code below calls a very standard and basic WCF service passing in the value if 42 and prints the result. The important part is that the send are receive actions are done inside of a CorrelationScope activity so this workflow can run in any host.

static Activity CreateWorkflow()

    var getDataResult = new Variable<string>();

    var send = new Send()

        OperationName = "GetData",

        ServiceContractName = "IService1",

        Endpoint = new Endpoint()

            Binding = new BasicHttpBinding(),

            AddressUri = new Uri("http://localhost:8080/GetDataService/")

},

        Content = new SendParametersContent()

            Parameters =

                {"value", new InArgument<int>(42)}

};

    var receive = new ReceiveReply()

        Request = send,

        Content = new ReceiveParametersContent

            Parameters =

                {"GetDataResult", new OutArgument<string>(getDataResult)}

};

    var workflow = new Sequence()

         Variables = { getDataResult },

         Activities =

            new CorrelationScope()

                Body = new Sequence()

                    Activities = { send, receive }

},

            new WriteLine() { Text = getDataResult } }

};

    return workflow;

Update: See here for the code when using a RequestReplyCorrelationInitializer.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Online Workflow 4 presentation

Maurice — Tue, 01 Dec 2009 16:29:00 GMT

Attached are the PowerPoint sheets and samples from my online Window Workflow Foundation 4 presentation today.

Let me know if you have any questions.

WF4Demo.zip

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Creating complex activities in the workflow designer

Maurice — Mon, 30 Nov 2009 12:31:18 GMT

Note: This blog post is written using the .NET framework 4.0 Beta 2

In Windows Workflow Foundation 4 there are a number of “activities” in the designer that aren’t really activities but activity templates. The most obvious of there are the ReceiveAndSendReply and the SendAndReceiveReply in the Messaging section of the toolbox.

If you search for either of these activities you are not going to find them. Their real name is ReceiveAndSendReplyFactory and SendAndReceiveReplyFactory respectively and they aren’t activities but activity templates.

So how to create an activity template?

Quite simply create a class and implement the IActivityTemplateFactory interface. This interface is simple and consists of a single Create function that returns the activity to be added to the workflow. Need to create multiple activities like the messaging activities do? Just wrap them in a Sequence activity and return that.

So what does that look like? Well in the case of the ReceiveAndSendReplyFactory the Create() looks like this according to Reflector:

public Activity Create(DependencyObject target)

    string str = ActivityDesignerHelper.GenerateUniqueVariableNameForContext(target, "__handle");

    Variable<CorrelationHandle> variable = new Variable<CorrelationHandle>

        Name = str

};

    VisualBasicSettings settings = new VisualBasicSettings

        ImportReferences =

            new VisualBasicImportReference

                Assembly = requiredAssemblyName,

                Import = requiredNamespace

};

    Receive receive = new Receive

        OperationName = "Operation1",

        ServiceContractName = XName.Get("IService", "http://tempuri.org/"),

        CorrelationInitializers =

            new RequestReplyCorrelationInitializer

                CorrelationHandle = new VisualBasicValue<CorrelationHandle>

                    ExpressionText = str,

                    Settings = settings

};

    return new Sequence

        Variables = { variable },

        Activities =

            receive,

            new SendReply

                DisplayName = "SendReplyToReceive",

                Request = receive

};

Nice to know what is happening behind the scenes and IActivityTemplateFactory is a nice interface to have when you start creating your own complex activities.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Online presentation: Meet the New Workflow WF4

Maurice — Mon, 30 Nov 2009 08:49:19 GMT

Tomorrow I will be doing an online presentation about Windows Workflow Foundation 4. The meeting lasts 1 hour and starts at 4PM European time, 3PM UTC or 7AM PST.

The goal is to provide an overview of WF4 and how to get started with it in Visual Studio 2010.

I will be doing the meeting using LiveMeeting and you can register here.

During the meeting I will also be tracking the Twitter hash tag #dmwf4 for additional questions and feedback.

“See” you there tomorrow

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

TryCatch activity in WF4

Maurice — Fri, 27 Nov 2009 06:47:03 GMT

Note: This blog post is written using the .NET framework 4.0 Beta 2

I can’t say I am a fan of the way the TryCatch activity is implemented in Windows Workflow Foundation 4.

For starters there is a Finally block where you can add some activities you want to execute. Sounds nice and very much like the try/catch/finally code construct we have in C# or Visual Basic. Except that it behaves in a subtlety different way. With the C# try/catch/finally the finally code will always run, whether you catch the exception or not. In fact you can just use a try/finally and it will work just fine.

With WF4 this is not the case though

The finally activity will only execute if the try block or one of the catch blocks completes. This means that an exception that is unhandled which bubbles terminating the workflow up will not cause the finally block to execute unless the host application forces it to do so by returning UnhandledExceptionAction.Cancel from the OnUnhandledException instead of UnhandledExceptionAction.Terminate (the default). A subtle difference and one that is likely to bite people because the normal code path is usually to have the try activity to complete normally.

Another issue I have is with the catch blocks and the cause of the exception.

As with a code catch block you get a reference to the exception. However where you normally would use the stack trace to see where the error occurred this is useless in Windows Workflow Foundation. After all that is only going to show you a few methods in the ActivityExecutor and the activity that was executed, not which instance and where in the activity tree. And by default there is no way to get to the offending activity

Turns out that Darren Headrick created a rather nice way to get to the offending activity through workflow tracking. Quite a nice solution but not entirely obvious and I am sad that a solution like this is needed. Still nice work from Darren though

public class WhosFaultWasThat : TrackingParticipant

    public string Name { get; set; }

    protected override void Track(TrackingRecord trackingRecord, TimeSpan timeout)

        if (trackingRecord is FaultPropagationRecord)

            Name = ((FaultPropagationRecord)trackingRecord).FaultSource.Name;

Besides the FaultSource you also get the Fault and a FaultHandler property which will tell you if there is a TryCatch activity that might handle it. I say might because while you can see that there is a TryCatch you can’t quite see its catch blocks so you don’t know if it will be caught or not.

This neat trick does show one important thing though.

If you want to know what is going on with your workflow and activities you need to use a TrackingParticipant and add it to the Extensions collections. No matter which execution module you choose, WorkflowInvoker, WorkflowApplication or WorkflowServiceHost, they all support this mechanism.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

CodeCamp jQTouch session

Maurice — Sat, 21 Nov 2009 18:05:01 GMT

If you are looking for the demo files from my CodeCamp presentation in the Netherlands you can download the notes here and the complete sample code here. No PowerPoint, after all this was a CodeCamp

And when my ISP is fully operational again the demo can be viewed online here.

Enjoy, I enjoyed organizing the CodeCamp and doing this presentation.

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Windows Workflow Foundation 4 and persistence

Maurice — Thu, 19 Nov 2009 19:44:01 GMT

Note: This blog post is written using the .NET framework 4.0 Beta 2

The whole persistence model has changed quite a but for WF4.

The persistence class out of the box is called SqlWorkflowInstanceStore and as the name suggests it saves workflow data in either SQL Server 2005 or 2008. It is based on the InstanceStore class to if you prefer some other store all you need to do is subclass the InstanceStore and create your own.

So what can we do with the SqlWorkflowInstanceStore?

We can attach it to either a WorkflowApplication or a WorkflowServiceHost and persist workflows when we want. Notice I left out the WorkflowInvoker. This can be used to run only short lived workflows and doesn’t support persistence.

The case of the WorkflowApplication is quite simple.

var instanceStore = new SqlWorkflowInstanceStore(connStr);

WorkflowApplication app = new WorkflowApplication(workflow);

app.InstanceStore = instanceStore;

app.Run();

Okay its a little more involved then that.

First of all you need to create a database to store the workflow state in. There are a couple of SQL files in the “C:\Windows\Microsoft.NET\Framework\v4.0.21006\SQL\en” folder. The two you need are SqlWorkflowInstanceStoreSchema.sql and SqlWorkflowInstanceStoreLogic.sql. I created a batch file to quickly recreate my persistence database like this:

osql -E -S .\sqlexpress -Q "Drop Database WorkflowInstanceStore"

osql -E -S .\sqlexpress -Q "Create Database WorkflowInstanceStore"

osql -E -S .\sqlexpress -d WorkflowInstanceStore -i SqlWorkflowInstanceStoreSchema.sql

osql -E -S .\sqlexpress -d WorkflowInstanceStore -i SqlWorkflowInstanceStoreLogic.sql

So with all this in place we still need to tell the WorkflowApplication when to persist the workflow. There are several ways to to this but one is to use the PersistableIdle callback. This will only fire when an InstanceStore has been provided. Options are to persist and unload the workflow, just unload the workflow or do nothing at all. The callback is just another function so you can make whatever decisions you like.

app.PersistableIdle = e => PersistableIdleAction.Persist;

Another option is to use the Persist activity. This will allow the workflow to decide on extra persistence points regardless of the workflow being idle.

How about the WorkflowServiceHost?

With the WorkflowServiceHost we get a couple of different choices. First of all we can just create a SqlWorkflowInstanceStore and set it like this:

var workflow = new Workflow1();

var baseAddress = new Uri("http://localhost:8080/MyWorkflow");

var host = new WorkflowServiceHost(workflow, baseAddress);

var connStr = @"Data Source=.\sqlexpress;Initial Catalog=WorkflowInstanceStore;Integrated Security=True;Pooling=False";

var instanceStore = new SqlWorkflowInstanceStore(connStr);

host.DurableInstancingOptions.InstanceStore = instanceStore;

host.Open();

Console.WriteLine("Listening...");

Console.ReadLine();

host.Close();

Simple but it doesn’t give us any control over when workflows are persisted. We don’t get quite the same control as with a WorkflowApplication in this case, all we can do is set a few timeout values using the WorkflowIdleBehavior like this:

var workflowIdleBehavior = new WorkflowIdleBehavior();

workflowIdleBehavior.TimeToPersist = TimeSpan.FromSeconds(10);

workflowIdleBehavior.TimeToUnload = TimeSpan.FromMinutes(1);

host.Description.Behaviors.Add(workflowIdleBehavior);

We can’t make any decisions based, just set time the workflow is idle before it is persisted and the same before it is unloaded.

Suppose we want some more control over the way the SqlWorkflowInstanceStore behaves. We can using the SqlWorkflowInstanceStoreBehavior. This is actually the same class as is used through the config file.

var connStr = @"Data Source=.\sqlexpress;Initial Catalog=WorkflowInstanceStore;Integrated Security=True;Pooling=False";

var behavior = new SqlWorkflowInstanceStoreBehavior(connStr);

behavior.InstanceCompletionAction = InstanceCompletionAction.DeleteNothing;

behavior.InstanceLockedExceptionAction = InstanceLockedExceptionAction.AggressiveRetry;

behavior.InstanceEncodingOption = InstanceEncodingOption.None;

host.Description.Behaviors.Add(behavior);

So that is all there is to it?

Not quite there is a little complexity when it comes to using the same SqlWorkflowInstanceStore with multiple WorkflowApplication instances. Note that the WorkflowServiceHost automatically takes care of this so no need to worry about that.

By default a SqlWorkflowInstanceStore will only work with a single WorkflowApplication. If you try to use it with mutiple workflow you can get a InstancePersistenceCommandException with the following message:

SqlWorkflowInstanceStore does not support creating more than one lock owner concurrently. Consider setting InstanceStore.DefaultInstanceOwner to share the store among many applications.

The trick is to set the DefaultInstanceOwner of the SqlWorkflowInstanceStore. The code isn’t hard but not exactly obvious either.

var instanceStore = new SqlWorkflowInstanceStore(connStr);

var instanceHandle = instanceStore.CreateInstanceHandle();

var createOwnerCmd = new CreateWorkflowOwnerCommand();

var view = instanceStore.Execute(instanceHandle, createOwnerCmd, TimeSpan.FromSeconds(30));

instanceStore.DefaultInstanceOwner = view.InstanceOwner;

// Do whatever needs to be dome with multiple WorkflowApplications

var deleteOwnerCmd = new DeleteWorkflowOwnerCommand();

instanceStore.Execute(instanceHandle, deleteOwnerCmd, TimeSpan.FromSeconds(30));

The key is the CreateWorkflowOwnerCommand that needs to be executed at the start. And when you use the CreateWorkflowOwnerCommand just make sure not to forget the DeleteWorkflowOwnerCommand otherwise all workflow will remain locked by the owner and can’t be reloaded by another SqlWorkflowInstanceStore

Quite a but more flexible than we had before but, specially with the WorkflowApplication, also quite a bit more work and not always as obvious as I would like it.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Comparing two Uri’s

Maurice — Fri, 13 Nov 2009 20:46:06 GMT

This one bit me today a bit unexpectedly.

I was comparing two Uri’s and was getting unexpected matches between two Uri’s that where quite clearly not the same. Turns out the when comparing Uri’s the Fragment, or anchor or part after the #, is not part of the comparison.

So the following unit test passes even though I would have expected it to fail!

[TestMethod]

public void TestTwoEqualUrisWithDifferentAnchorShouldNotBeEqual()

    var baseUri = new Uri("http://www.test.com");

    var uri1 = new Uri(baseUri, "#anchor1");

    var uri2 = new Uri(baseUri, "#anchor2");

    Assert.AreEqual(uri1, uri2);

    Assert.AreNotEqual(uri1.ToString(), uri2.ToString());

Note that when comparing uri1 and uri2 they are equal even though they use two different anchor tags. Comparing the ToString() results does show the difference though. Wasted another bit of time on this piece of trivia

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Sending mail messages through Gmail

Maurice — Wed, 11 Nov 2009 19:24:48 GMT

recently I had to send a bunch of identical email messages for the CodeCamp we are organizing. Now there are plenty of ways to do this but I decided to write a little program using C# to send them. And just to make sure I can find the code next year

var from = new MailAddress("<<your email>>", "<<your name??");

var to = new MailAddress("<<destination address>>", "<<their name>>");

var message = new MailMessage(from, to);

message.Subject = "The subject";

message.Body = "The message body";

message.IsBodyHtml = true;

var host = "smtp.gmail.com";

var client = new SmtpClient(host, 587);

client.EnableSsl = true;

client.Credentials = new NetworkCredential("<<your username>>", "<<your password>>");

client.Send(message);

Easy as that.

Few things to note. I used a different sender address as we wanted all replies to end up in a shared mailbox instead of mine. Worked just fine even though I used my own account details to send.

There is a check on the number of messages send in a short time span. Not sure what the limit is, it seemed something like 100 per minute, but I had to add some sleep time between messages in order to send them all. No big deal but something to keep in mind.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

CodeCamp 2009: Sessies en OpenSpace

Maurice — Tue, 10 Nov 2009 08:02:00 GMT

Als eerste: de sessies voor de CodeCamp 2009 zijn bekend en staan online op http://www.codecamp.nl We denken dat het een erg interessante mix van sessies is, met genoeg sessies voor iedereen om een aantal interessante onderwerpen voor iedereen. De agenda ziet er nu als volgt uit:

09:30 - 10:45
Around .net framework 4.0 in an hour (Ronald Guijt)
ASP.Net - MVC 2.0 (Sander Gerz)
Windows Mobile en het werken met data (Arjan van Huizen)

11:00 - 12:15
ADO.NET EF 4.0 (Kurt Claeys)
SharePoint Nightmares (Marianne van Wanrooij)
iPhone development met jQTouch (Maurice de Beijer)

13:15 - 14.30
VSTO 2010 met Office 2010 (Hassan Fadili)
Modulaire Silverlight apps met Prism (Timmy Kokke)
Microsoft Surface Development (Freena Eijffinger & Dennis Vroegop)

14:45 - 16:00
VSTS 2010 (Pieter de Bruijn)
Windows Identity Foundation (Michiel van Otegem)
SQL Azure (Marcel Meijer)

Naast deze sessies hebben we ook nog de OpenSpace sessies. Daar hebben we geen agenda voor maar dat ligt nu eenmaal in de aard van een OpenSpace gebeuren. In het kort komt het neer op het volgende: als je iets hebt waar je graag met een aantal mensen over wilt discussieren, schrijf je dat 's ochtends op een flip-over. Mochten mensen dat interessant vinden, dan kunnen ze een stem uitbrengen op dat onderwerp. In de lunchtijd (van 12:15 - 13:15) is dan de keuze aan de mensen waar ze heen gaan en aan welke discussie ze mee willen gaan doen. Heeft jouw sessie genoeg stemmen dan komen de mensen vanzelf wel naar je toe, zo niet: dan is je sessie blijkbaar niet interessant voor een grote groep. Het idee is dat we een aantal van deze sessies tegelijkertijd hebben zodat mensen kunnen kiezen wat ze doen. De inhoud van de lunch sessies laten we dus volledig aan de bezoekers over!

Denk eens na over sessies of onderwerpen en discussieer mee met je mede-ontwikkelaars over jouw favoriete onderwerp!

Ik kan haast niet wachten tot het 21 november is..

Flowcharts in Workflow 4 and the Switch activity

Maurice — Tue, 27 Oct 2009 13:48:00 GMT

Note: This blog post is written using the .NET framework 4.0 Beta 2

Flowcharts are a nice addition to Windows Workflow Foundation 4. They allow for a lot of pretty complex behavior that is hard to do in a sequential workflow. In WF 3 we used to model these complex behaviors as state machine workflows. That worked but they weren't really state machines or event driven and things could get a bit tricky.

Enter the flowchart in Windows Workflow Foundation 4

One of the good things is that a flowchart is not another workflow type. No it is just another activity to drop in a workflow. So you are free to combine sequential work with a flowchart in one workflow. For example you can have a Sequence activity containing a Flowchart activity and that in turn can contain another Sequence activity which can contain another …. I guess you get the picture.

Below a Flowchart containing a mix of a FlowSwitch and a FlowDecision activity, which are only usable in a Flowchart, and some other general activities like a WriteLine and an Assign activity.

So far so good.

The one thing I don’t like is the FlowSwitch activity

The problem with the FlowSwitch is that the activity takes an expression determining the branch to execute and each branch has a case property to determine which branch is executed. Sounds like a good plan except when you start trying things. What I did was add a Random variable named rnd to the workflow so different branches would execute. To do this I added the following expression to the FlowSwitch:

rnd.Next(5)

Next in each of the first 3 cases I entered 1, 2 and 3 leaving the 4th as default. Sounds good right?

Well not quite!

When I ran the sample I would only get Default printed to the console. Well I guess with Random that is possible to try again. And again.

Hmm something must be wrong here.

It turns out all the cases are of type string and the expression is of type Int32. Those are never going to match! But there are no compile or runtime errors either. I am sure this is going to bite me some time in the future

Of course the FlowSwitch should just to a ToString() on the expression result, anything else would be pointless as any comparison fails. But as it doesn’t we have to do so ourselves. So I changed the Expression to:

and everything works as expected.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Workflow 4 and Visual Basic expressions

Maurice — Mon, 26 Oct 2009 15:20:46 GMT

Note: This blog post is written using the .NET framework 4.0 Beta 2

When using Windows Workflow Foundation 4 you often need to enter expression in some activity property. The new thing is these expressions are all in the Visual Basic dialect regardless of what language you project is in. So when developing a project in C# the expressions are sill in Visual Basic.

Weird right?

Well not really when you think about it!

After all power business users are expected to be able to modify workflows. And guess what their favorite tools are. That would be Microsoft Excel and Word. And what do they use to create macros? Right Visual Basic for Applications is their language of choice.

So if they use VBA letting them enter VB into expression dialogs is a far more natural fit than having them use C#.

A case for the Delay activity

So lets take a look at the delay activity. This activity takes 1 input property Duration of type Time Span. So I guess that means our VBA power users are going to have to enter something like if they want to wait 5 seconds:

Now for some reason I suspect that is not the first thing they are going to type. In fact they are more likely to time something like “0:0:05” instead. Not very VB like right?

Well it turns out workflow is smart enough to realize it can convert the string literal to a Time Span and use this. So when our power users does the following it just works

Nice, I like this!

Enjoy WF4!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Call for speakers: 3rd Dutch Code Camp

Maurice — Mon, 26 Oct 2009 10:26:42 GMT

Op 21 november 2009 organiseren de SDN, de dotNED User Group en VBcentral.nl samen de derde Nederlandse Code Camp. Een unieke dag, voortkomend uit een unieke samenwerking. Kenmerkend aan deze dag is, dat het een evenement is dóór ontwikkelaars en vóór ontwikkelaars!

We zijn op zoek naar collega ontwikkelaars die het leuk vinden om ook een sessie voor hun rekening te nemen. Er is ruimte voor de meer traditionele sessies, maar bijvoorbeeld ook voor Chalk & Talk sessies. In principe is zijn de mogelijke onderwerpen zeer divers en worden door ons op voorhand niet beperkt. Ben jij geïnteresseerd om ook een sessie te doen? Laat het ons weten! Ook als je geen of nog niet zoveel sprekerservaring hebt ben je meer dan welkom. Indien je dat wilt willen we je hier best mee helpen.

Het evenement vindt plaats in Rotterdam en meer informatie kun je vinden op de Code Camp website:www.codecamp.nl

We zien graag jouw sessievoorstel tegemoet! Stuur deze zo snel mogelijk naar: andre@obelink.com.

Een lijstje van onderwerpen waar deelnemers ondermeer om vragen:

Architectuur/Design patterns
Frameworks
Surface
.NET 4/3.5
Visual Studio 2010
VSTS
Open Source
SharePoint
ASP.NET/MVC/Web development/Silverlight
Windows 7
iPhone
DNN
VSTO
LINQ
SQL Server 2008
Geneva
BizTalk
Windows Presentation Foundation
Windows Communication Foundation
Windows Workflow Foundation

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Nederlandse CodeCamp 2009

Maurice — Mon, 19 Oct 2009 10:26:00 GMT

Op 21 november 2009 organiseren de SDN, Stichting dotNed en VBcentral samen het derde Nederlandse Code Camp. Dit is een dag lang met code, code sharing, freaking en gezellig samenzijn. Een evenement door ontwikkelaars, voor ontwikkelaars. De regie ligt voor een belangrijk deel bij de deelnemers! Het aantal plaatsen voor deelnemers is wel beperkt tot maximaal 150. Wacht dus niet te lang met beslissen want voor je het weet is er geen plaats meer. Vergeet bij je aanmelding niet op te geven welke onderwerpen je interesse hebben. Bovendien nodigen we iedereen graag uit om zelf een sessie in te vullen.

Op de website, www.codecamp.nl, vind je meer informatie en kan je je aanmelden.

Nationale Office Dag files

Maurice — Thu, 15 Oct 2009 20:54:43 GMT

Looking for the slides and samples from my two presentations at the Nationale Office Dag in Ede? You can download them from here.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

WF4&WCF and message correlation

Maurice — Wed, 02 Sep 2009 15:27:34 GMT

Note: This blog post is written using the .NET framework 4.0 Beta 2

In the previous blog posts, here, here and here, I demonstrated how to use WCF from WF4. This same some more about sending multiple messages to the same workflow, AKA Workflow Correlation.

One of the ugly parts of Windows Workflow Foundation 3 was the message correlation part when you used WCF to send multiple messages to the same workflow.

When using WF3 you where forced to use one of the context bindings like BasicHttpContextBinding or WSHttpContextBinding. Not only that but you also had to retrieve and set the correlation context using the IContextManager and set it to some arcane guid. This guid was the workflow instance ID but having to use that on the client means the client had to be very aware of the server technology used, something that goes against the principals of WCF. Using something in the message itself as to route the message to the correct workflow was just not possible with the build-in activities.

Fortunately the WF4 story is much better. No longer do we need to use the “context” bindings but the standard WCF bindings will do just fine. And the client doesn’t have to work with the workflow instance id but can pass some more logical data, like an invoice number, that will be mapped to the correct workflow. Much better!

To demonstrate this we first need to expand the workflow so it can receive multiple messages for the same workflow. The input for both Receive activities will still be the same person class from the previous example and we will use the persons ID to route the messages.

The new workflow definition looks like this:

private static WorkflowElement CreateWorkflow()

    var result = new Sequence();

    var input = new Variable<Person>();

    result.Variables.Add(input);

    XNamespace ns = "http://tempuri.org";

    var handle1 = new Variable<CorrelationHandle>();

    result.Variables.Add(handle1);

    var handle2 = new Variable<CorrelationHandle>();

    result.Variables.Add(handle2);

    var receive1 = new Receive()

        OperationName = "Operation1",

        ServiceContractName = ns + "MyService",

        Value = new OutArgument<Person>(input),

        AdditionalCorrelations = {

           {"ChannelBasedCorrelation", new InArgument<CorrelationHandle>(handle1)}

},

        CorrelationQuery = CreateCorrelationQuery(),

        CanCreateInstance = true

};

    result.Activities.Add(receive1);

    var write1 = new WriteLine()

        Text = new InArgument<string>(env => string.Format("\tThe workflow was called with '{0}'.", input.Get(env)))

};

    result.Activities.Add(write1);

    var reply1 = new SendReply()

        Request = receive1,

        Value = new InArgument<string>("The result")

};

    result.Activities.Add(reply1);

    var receive2 = new Receive()

        OperationName = "Operation2",

        ServiceContractName = ns + "MyService",

        Value = new OutArgument<Person>(input),

        AdditionalCorrelations = {

           {"ChannelBasedCorrelation", new InArgument<CorrelationHandle>(handle2)}

},

        CorrelationQuery = CreateCorrelationQuery()

};

    result.Activities.Add(receive2);

    var write2 = new WriteLine()

        Text = new InArgument<string>(env => string.Format("\tThe workflow was called again with '{0}'.", input.Get(env)))

};

    result.Activities.Add(write2);

    var reply2 = new SendReply()

        Request = receive2,

        Value = new InArgument<string>("The second result")

};

    result.Activities.Add(reply2);

    return result;

This is very similar to the previous workflow except we have two Receive activities and only the first is configured to allow the message to create a new instance.

The trick in getting the second message routed to the same workflow is by setting the CorrelationQuery on the two Receive activities. This is done in the CreateCorrelationQuery() function as follows:

private static CorrelationQuery CreateCorrelationQuery()

    var result = new CorrelationQuery();

    var xpath = new XPathMessageQuery()

        Namespaces = new XmlNamespaceManager(new NameTable()),

        Expression = "//sample:Person/sample:Id"

};

    xpath.Namespaces.AddNamespace("sample", "urn:WF4Sample:person");

    var messageQuerySet = new MessageQuerySet()

        Name = "RequestCorrelation"

};

    messageQuerySet.Add("PersonId", xpath);

    result.Select = messageQuerySet;

    return result;

The important part here is that the MessageQuerySet key value and the related Expression XPath must produce the same result for both request. Something that is easy here as I am sending in the same person object twice.

So the regular client has hardly any changes. All that is needed is the addition of the second operation to the ServiceContract like this:

[ServiceContract]

interface MyService

    [OperationContract]

    Operation1Response Operation1(Person request);

    [OperationContract]

    Operation1Response Operation2(Person request);

And calling the second operation like this.

static void Main(string[] args)

    var binding = new BasicHttpBinding();

    var endpoint = new EndpointAddress("http://localhost:8090/Sequence1/Operation1");

    var factory = new ChannelFactory<MyService>(binding, endpoint);

    var proxy = factory.CreateChannel();

    var request = new Person()

        Id = 23,

        FirstName = "Joe",

        LastName = "Regular",

        BirthDate = new DateTime(1975, 7, 1)

};

    var result = proxy.Operation1(request);

    Console.WriteLine(result.Value);

    //request.Id = 99;

    request.FirstName = "Maurice";

    request.LastName = "Chevalier";

    request.BirthDate = new DateTime(1888, 9, 12);

    result = proxy.Operation2(request);

    Console.WriteLine(result.Value);

    Console.WriteLine("Regular client is done.");

    Console.ReadLine();

Note that I cam completely free to change the person object as long as I use the same Id. Should I change the Id the WorkflowServiceHost would try and find an existing workflow with the changed person Id, fail and throw a FaultException with message “The requested operation could not complete because instance key '4d7e998a-4cff-4743-3dd4-2afd5578383c' could not be found.”. Not quite sure where the Guid comes from but there is no workflow with that instanceId.

The good thing here is that the client doesn’t need to be aware of the workflow implementation on the server and the server can use “regular” message data to determine the correct workflow to send the message to.

The Workflow client has about the same change. In this case the Send activity is duplicated but other that that there is very little change and certainly no code that makes the client workflow aware of the service workflow.

private static WorkflowElement CreateWorkflow()

    var result = new Sequence();

    XNamespace ns = "http://tempuri.org";

    var endpoint = new Endpoint()

        Uri = new Uri("http://localhost:8090/Sequence1/Operation1"),

        Binding = new BasicHttpBinding()

};

    var response = new Variable<string>();

    result.Variables.Add(response);

    var handle = new Variable<CorrelationHandle>();

    result.Variables.Add(handle);

    var person = new Person()

        Id = 7,

        FirstName = "Maurice",

        LastName = "de Beijer",

        BirthDate = new DateTime(1962, 8, 24)

};

    var request = new Send()

        OperationName = "Operation1",

        Endpoint = endpoint,

        AdditionalCorrelations =

           {"ChannelBasedCorrelation", new InArgument<CorrelationHandle>(handle)}

},

        ServiceContractName = ns + "MyService",

        Value = new InArgument<Person>(person)

};

    result.Activities.Add(request);

    var reply = new ReceiveReply()

        Request = request,

        Value = new OutArgument<string>(response)

};

    result.Activities.Add(reply);

    var write = new WriteLine()

        Text = new InArgument<string>(response)

};

    result.Activities.Add(write);

    var delay = new Delay()

        Duration = TimeSpan.FromSeconds(5)

};

    result.Activities.Add(delay);

    var request2 = new Send()

        OperationName = "Operation2",

        Endpoint = endpoint,

        AdditionalCorrelations =

           {"ChannelBasedCorrelation", new InArgument<CorrelationHandle>(handle)}

},

        ServiceContractName = ns + "MyService",

        Value = new InArgument<Person>(person)

};

    result.Activities.Add(request2);

    var reply2 = new ReceiveReply()

        Request = request2,

        Value = new OutArgument<string>(response)

};

    result.Activities.Add(reply2);

    var write2 = new WriteLine()

        Text = new InArgument<string>(response)

};

    result.Activities.Add(write2);

    return result;

Conclusion.

The WF3/WCF marriage in Wf3.5 left quite a bit to be desired and fortunately live has become a lot simpler with WF4.

Enjoy!