The Problem Solver : DevCenter

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

WF4&WCF and message correlation

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

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!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Sending your own objects to a WF4 workflow

Maurice — Thu, 20 Aug 2009 13:11:00 GMT

In the previous two blog posts (here and here) I showed how to create and expose a Windows Workflow Foundation 4 workflow via WCF and have both a workflow and a regular C# client work with it. But the parameter and return value where real simple with just a string each. So how about passing some more complex data.

To show how to do so I will replace the singe string with a person object. Admittedly not the most complex person with only an id, first and last name and their birth date but enough to demonstrate the principal.

The main of the service, which uses a WorkflowServiceHost, stays exactly the same so see the first blog post for that part. The CreateWorkflow() function will change now reflecting the fact that the service will no longer expect a string but a person object.

private static WorkflowElement CreateWorkflow()

    var result = new Sequence();

    var input = new Variable<Person>();

    result.Variables.Add(input);

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

    var handle = new Variable<CorrelationHandle>();

    result.Variables.Add(handle);

    var receive = new Receive()

        OperationName = "Operation1",

        ServiceContractName = ns + "MyService",

        Value = new OutArgument<Person>(input),

        AdditionalCorrelations = {

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

},

        CanCreateInstance = true

};

    result.Activities.Add(receive);

    var write = new WriteLine()

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

};

    result.Activities.Add(write);

    var reply = new SendReply()

        Request = receive,

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

};

    result.Activities.Add(reply);

    return result;

Not a big change really as we only have to change the input variable from Variable<string> to Variable<Person> and do the same with the Value property of the Receive activity which goes from new OutArgument<string>(input) to new OutArgument<Person>(input).

That leaves the Person class and this is just straightforward WCF work by turning the basic class into a data contract.

[DataContract(Namespace = "urn:WF4Sample:person")]

public class Person

    [DataMember]

    public int Id { get; set; }

    [DataMember]

    public string FirstName { get; set; }

    [DataMember]

    public string LastName { get; set; }

    [DataMember]

    public DateTime BirthDate { get; set; }

    public override string ToString()

        return string.Format("{0} {1} was born on {2} (ID: {3})", FirstName, LastName, BirthDate, Id);

Again no big deal

So with the service done we need to make the same changes to the two client applications. First the workflow client using the Send activity.

The Person class is exactly the same as on the server so just copy the code as is. Again the main in the workflow client doesn’t change, see the first blog post for that part. The part that does change a little is the CreateWorkflow() function so it creates and sends a Person instead of a string. The code goes as follows:

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);

    return result;

Again a very minor change.

So how about the C# console client from the second blog post?

The service contract changes a little and is now:

[ServiceContract]

interface MyService

    [OperationContract]

    Operation1Response Operation1(Person request);

The person class is very different from the service though and looks like this:

[MessageContract(WrapperNamespace = "urn:WF4Sample:person")]

internal class Person

    [MessageBodyMember(Namespace = "urn:WF4Sample:person")]

    public int Id { get; set; }

    [MessageBodyMember(Namespace = "urn:WF4Sample:person")]

    public string FirstName { get; set; }

    [MessageBodyMember(Namespace = "urn:WF4Sample:person")]

    public string LastName { get; set; }

    [MessageBodyMember(Namespace = "urn:WF4Sample:person")]

    public DateTime BirthDate { get; set; }

But besides the difference from using a message contract as opposed to a data contract this isn’t a big deal.

The main program changes a bit but not a whole lot. Again the only changes are due to the fact we are passing in a Person instead of a string.

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);

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

    Console.ReadLine();

All together not bad.

But so far we have only used a very simple workflow with a single message send to it. Suppose you want to send multiple messages to the same workflow? Well in that case we need to use message correlation as we will see next time.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Combined DevelopMentor instructors blog feed.

Maurice — Wed, 19 Aug 2009 07:37:12 GMT

Michael Kennedy, one of the co instructors from DevelopMentor, has created a combined feed from all the blogs of the various DevelopMentor. An awesome group of people with a lot of knowledge to share. Highly recommended in you RSS reader.

http://feeds.feedburner.com/DevelopmentorInstructors

If you want to check out a list of the individual blog feeds look here.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Using ASP.NET MVC

Maurice — Thu, 13 Aug 2009 17:26:44 GMT

Recently I started using ASP.NET MVC for a real project. SO far I had been reluctant to use ASP.NET MVC as it meant giving up on the post back model that so many of the available ASP.NET controls depend on. Yet a lot of people I know and respect where saying good things about ASP.NET MVC so I decided to try it out on a small but real project.

Well the project isn’t finished yet but I am a convert

Using ASP.NET MVC is much nicer that I expected it to be. Sure the post back model, and with it a lot of controls, are gone but I started doing more client side stuff using jQuery and the many plug-ins available. And even where not doing a lot of client side work ASP.NET MVC makes live quite easy.

The main difference is that ASP.NET MVC lends itself very well to test driven development. Now I not a pure TDD zealot but covering a lot of the code with unit test, regardless if you create the test first or later, is pretty much a requirement of a good software project. And ASP.NET MVC lend itself much better to unit testing than ASP.NET web forms.

ASP.NET MVC will not be the thing for everyone. If you are heavy into designers and drag-drop development web forms will be a better match for you. But if you are like me and like working with code ASP.NET MVC is a joy to work with.

The book I keep by my side is Steven Sanderson’s Pro ASP.NET MVC Framework. It has been very valuable, both on giving me a behind the scenes insight and solving some practical issues I ran into.

Error Logging Modules and Handlers for ASP.NET (MVC)

Maurice — Thu, 13 Aug 2009 12:40:20 GMT

I am working on a new ASP.NET MVC app and like so many other applications out there I need to log any errors should they occur. recently I heard about ELMAH Error Logging Modules and Handlers for ASP.NET through this blog post of Scott Hanselman. So as using en existing and proven solution is always better that reinventing the wheel I decided to try ELMAH and see how easy it is to get started.

Well I can only say I am positively amazed at how easy it is.

Starting from scratch it took me less that 2 hours to download and integrate it into my current ASP.NET MVC application and log all errors to SQL Server. That is including security so not everyone can check the error log.

There are lots of additional capabilities I haven’t looked at yet like setting up an RSS feed, emailing or even tweeting errors messages. But judging from the experience so far that should prove easy enough.

My only regret is that I didn’t check it out before.

Checkout the project run by Atif Aziz here.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

What does Windows Workflow Foundation 4 mean for existing workflow developers?

Maurice — Fri, 03 Jul 2009 20:12:54 GMT

The question of what Windows Workflow Foundation version 4 means for developers currently developing using WF recently came up. As I mentioned before WF 4 is a complete rewrite and doesn’t use any of the existing WF 3 classes. The design of WF 4 is even quite different from the design of WF 3.

So are WF 3 developers completely left in the dark and have to start from scratch? And what about their existing applications, will they still run on .NET 4 or are they stuck in .NET 3.5 until the end of times?

Fist of all let me address why I believe Microsoft could make such a radical change. Keep i mind this is just my personal opinion and I might be completely wrong .

WF 3 was never widely adopted so I believe the team felt they could do this and not create too much of a problem. Personally I don't think the low adoption of WF 3 had anything to do with the technology. Sure it has its problems but most people never got to the point that they ran into real technical issues. Instead most people looked, didn't understand and quit. So IMHO the main problem was far more a question if evangelism that technology.

So what is the big issue with a migration from WF 3 to WF 4?

One big issue with WF 4 is that Microsoft decided not to release a state machine implementation. In WF 3 there was a choice between state machine and sequential workflows. In WF 4 there is a choice between sequential and flow chart. And in WF 3 a state machine turned out to be far more flexible and useful and quite a few cases are not really covered by the WF 4 model. There are a few workarounds to do something like a state machine in WF 4 but they are not pretty. That said, a number of state machine workflows could very well be done using a flow chart.

As far as backward compatibility the story is a bit more complicated. WF 4 ships with an interop activity you can use to host custom WF 3 activities in a WF 4 workflow. How good or bad this is? I really don't know yet but given how different the two designs are I fear it is very limited.

But WF 3 developers need not worry about their existing projects!

There is however a second side to the compatibility story. .NET 4 will ship both with the WF 3 and the WF 4 runtimes. The WF 3 runtime will not be prominent but it will still be there so all existing WF 3 applications will continue to run as is. And because it is part of the current .NET framework I suspect this is a legal requirement (but then I am no lawyer so could be wrong here). So there is no reason for existing workflow developers to panic just yet .

So existing workflow developers should start learning WF 4 for future projects but can continue to keep using their existing WF 3 solutions for the foreseeable future.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Getting started with the .NET RIA Services

Maurice — Tue, 30 Jun 2009 16:34:38 GMT

A recent article I wrote for the MSDN website just went live.

Read is here.

Passing data into a Windows Workflow Foundation 4 workflow

Maurice — Tue, 30 Jun 2009 13:51:03 GMT

Passing parameters into a workflow is similar in WF4 as it was in WF3.

In both case a Dictionary<string, object> is passed in when creating the workflow instance object. Alternatively when using the WF4 WorkflowInvoker you can pass it into the Invoke() method.

This is quite simple but I have never been a fan of the very loose coupling here. basically on the outside you have to create a dictionary with as key something inside of the workflow. No compile time checking. No improvement where, unless you consider the somewhat easier unit testing with the WorkflowInvoker.

The actual behavior between WF3 and WF4 is quite different however.

In Wf3 if you pass in a key that doesn’t match up you get a System.Reflection.TargetInvocationException with a System.InvalidOperationException inner exception with the text: “This operation can not be performed at runtime.”. Great help in debugging

In WF4 on the other hand you get no error at all. The value is just ignored so it is even harder to detect typos. Well I guess not every change can be an improvement. And just in case you where thinking “But a unit test will take care of that right?” keep in mind that workflows tend to be complex and long running things not very well suited to unit testing.

Starting a workflow with a parameter:

Shared Sub Main()

    Dim inArgs As New Dictionary(Of String, Object)

    inArgs("Name") = "Maurice"

    Dim myInstance As WorkflowInstance = New WorkflowInstance(New Sequence1(), inArgs)

    myInstance.OnCompleted = AddressOf OnWorkflowCompleted

    myInstance.OnAborted = AddressOf OnWorkflowAborted

    myInstance.OnUnhandledException = AddressOf OnWorkflowUnhandledException

    myInstance.Run()

    syncEvent.WaitOne()

End Sub

So where is this Name value actually stored?

Well in WF3 that would have been stored in a property, possibly a dependency property, or a field. The types must match, exactly.

In WF4 the notion of properties and fields is gone. No more dependency properties to tie everything together. So instead we have Variables and Arguments. Basically a variable is just like a variable in a function, only here it holds some value for an activity. Big difference is that a Variable is in scope, i.e. visible, to all nested activities as well. So basically it is a way of sharing state between different activities.

To allows us to pass data into a workflow, or get something out, we need to use an Argument.

In this case I have defined two arguments, the Name to pass into the workflow and the Greeting that will be the result of the workflow.

Getting the result out is done in the OnCompleted delegate. This delegate is passed a WorkflowCompletedEventArgs which in turn contains another dictionary with all out argument.

Shared Sub OnWorkflowCompleted(ByVal e As WorkflowCompletedEventArgs)

    Dim greeting As String = e.Outputs("Greeting")

    Console.WriteLine(greeting)

    syncEvent.Set()

End Sub

Again not very different from WF3 where we used the WorkflowCompleted event and the OutputParameters dictionary from the WorkflowRuntime.

Conclusion

While there are quite a few differences in the details the basic approach remains the same. And as the old approach with dictionaries was rather error prone I consider this a missed chance

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

The new Windows Workflow Foundation 4 runtime

Maurice — Tue, 23 Jun 2009 09:20:04 GMT

With WF3 there was a central workflow runtime environment called the WorkflowRuntime and used to manage the lifetime of workflow instances. In WF4 this central class no longer exists and we manage individual workflows.

To compare the two, this is what a minimal console application looks like in WF3. It basically runs a workflow and prints a message when done:

static void Main(string[] args)

    using (WorkflowRuntime workflowRuntime = new WorkflowRuntime())

        workflowRuntime.WorkflowCompleted += delegate(object sender, WorkflowCompletedEventArgs e)

            Console.WriteLine("The workflow has completed.");

};

        WorkflowInstance instance = workflowRuntime.CreateWorkflow(typeof(WorkflowConsoleApplication1.Workflow1));

        instance.Start();

        Console.WriteLine("Waiting for the workflow to complete.");

        Console.ReadLine();

The same functionality in WF4 looks very different:

static void Main(string[] args)

    WorkflowInstance myInstance = new WorkflowInstance(new Sequence1());

    myInstance.OnCompleted += delegate(WorkflowCompletedEventArgs e)

        Console.WriteLine("The workflow has completed.");

};

    myInstance.Run();

    Console.WriteLine("Waiting for the workflow to complete.");

    Console.ReadLine();

The most important thing to note is that there is no longer a WorkflowRuntime object, instead we create a new WorkflowInstance object passing in a workflow instance (compared to a workflow type before).

There are some benefits as well as drawbacks to not having a WorkflowRuntime.

The main benefit is that it makes creating and running workflows much easier. No longer do we need to keep track of a singleton and use that to do everything. Another benefit is we can register event handler per workflow instance, makes it easier to do different things for different types of workflows. In fact the OnCompleted isn’t an event but a delegate so you can add only a single handler.

The drawback is that general configuration. Like recording workflow errors, tracking execution or workflow persistence must be done for each instance while before we could just do it on the workflow runtime.

Some things haven’t changed. In both WF3 and WF4 running the workflow is done asynchronously so we need to wait, in both cases done using a Console.ReadLine().

Synchronous execution

With WF3 it was hard to have a workflow execute synchronously. Basically we had to add a different scheduler to the workflow runtime and explicitly tell the scheduler to execute the workflow. Of course this would affect every workflow created through the same WorkflowRuntime.

With WF4 there is a much easier model using the WorkflowInvoker class. All we need to do is call WorkflowInvoker.Invoke() passing in the workflow object and the workflow will execute synchronously on the same thread. Not only very useful for running the odd workflow but also for unit testing as any WorkflowElement, the base class for all activities, can be executed this way.

static void Main(string[] args)

    WorkflowInvoker.Invoke(new Sequence1());

    Console.WriteLine("The workflow has completed.");

    Console.ReadLine();

Nice right!

Enjoy.

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Getting started with Windows Workflow Foundation 4

Maurice — Mon, 22 Jun 2009 13:18:11 GMT

As you may have heard Windows Workflow Foundation 4 is not an upgrade from Windows Workflow Foundation 3 (or 3.5). The version numbers might suggest that the previous version was quite mature but in fact it refers to the version of the .NET framework. In fact Windows Workflow Foundation 3 was the first version and 3.5 added only very few features and some bug fixes. And as WF 4 is a complete rewrite we should approach it as a new product and forget just about everything we already know about WF 3.

That might be a bit surprising, after all we still have activities and a workflow runtime right?

Well wrong actually!

There no longer is a class named WorkflowRuntime. Creating workflows is done by creating a WorkflowInstance object. This object is raises events for that workflow and only for that specific workflow.

But surely there is still an Activity base class?

Yes there is. But this is a completely new class that has nothing to do with the class Activity that was used with WF 3. In fact the new Activity class is in a new assembly and namespace, the full name is System.Activities.Activity in the assembly System.Activities.dll. The “old” activity class was System.Workflow.ComponentModel.Activity in the System.Workflow.ComponentModel.dll assembly. The old class still exists in .NET 4 so old workflows will still run but the new classes have no relation with the old classes.

So basically forget all you knew about the behavior of WF 3

So lets take a brief look at creating a new workflow 4 style workflow.

When we start Visual Studio 2010 and select File/New/Project we get the new project tab. Select the Workflow node and you will see the four new project types

More about the different types in another blog post. For now just select the “Sequential Workflow Console Application”.

What we end up with is a simple project with just 2 files, the program.cs and the Sequence1.xaml. The latter contains the workflow. Note there is no choice between code or xaml workflows, the designer only works with xaml based workflows. Also note that the extension is no longer XOML but has changed to XAML.

The Sequence1.xaml workflow is still empty and looks like this:

When we open the Toolbox we see the new collection of basic activities. These are also completely new. For now just drag a WriteLine activity onto the Sequence in the designer. The goal of the WriteLine activity is just what the name suggest: write a line of text to some form of output stream. When we open the property sheet with the WriteLine activity selected we see there are just three properties: the DisplayName, the Text and the TextWriter.

The DisplayName is actually the name used on the design surface and used during the design of the workflow.

The Text property contains the text we want to print. In the property sheet we see a textbox with the text “<Enter an expression>”. This really is an expression editor where you can type in code. So if you want to enter a simple fixed text you must use quotation marks around it. This must always be a valid Visual Basic statement. yes that isn’t a typo Visual Basic, not C#, even if you are developing a C# project.
So in this case just add “Hello Workflow 4” including the quotation marks.

The TextWriter property is the text stream to write the text to. This is also an expression, just like the Text, and is optional. When not specified the text will be written to Console.Out which will do fine for now.

These expression windows in VB are completely new and a big change from WF3. Where we previously had to bind to property binding or something similar to add custom code we can now type it directly into the designer.

With this in place we are ready to run the workflow. Press Ctrl+F5 and with a bit of luck you should see the output appear in the console window. You might need a bit of luck because it appears the current bits are still a bit unstable and on my laptop running Windows 7 the designer tends to lock up quite a bit

In the next post more about how the workflow is created and started at runtime.

Paging with the Silverlight RIA services DomainDataSource

Maurice — Mon, 27 Apr 2009 08:57:46 GMT

Using the declarative DomainDataSource that is part of the upcoming Silverlight 3 RIA services makes it quite easy to work with data. All you need to do is add a DomainDataSource control to the the XAML, point it to the generated DomainContext class (in this case NorthwindContext) and tell it which method to use to load the data from the web service(in this case LoadCustomers). Next add a DataGrid to display the data and you are good to go.

     <UserControl xmlns:dataControls="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data.DataForm"  x:Class="LOBUsingRIAServices.CustomerListPage"

                 xmlns:data="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data"  

                 xmlns:riaControls="clr-namespace:System.Windows.Controls;assembly=System.Windows.Ria.Controls"

                 xmlns:web="clr-namespace:LOBUsingRIAServices.Web"

                 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 

                 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

        <Grid x:Name="LayoutRoot" Background="White">

            <riaControls:DomainDataSource x:Name="CustomerDataSource"

                                          LoadMethodName="LoadCustomers">

                <riaControls:DomainDataSource.DomainContext>

                    <web:NorthwindContext />

                </riaControls:DomainDataSource.DomainContext>

            </riaControls:DomainDataSource>

            <data:DataGrid ItemsSource="{Binding Data, ElementName=CustomerDataSource}" />

        </Grid>

    </UserControl>

Pretty simple and that is the way I like it

Adding paging.

Sometimes the lost of data to load can get somewhat large and you might not want to load all data. In that case all you need to do is add a PageSize and the DomainDataSource will only load enough data to display on a single page. You can do this by just setting the PageSize on the DomainDataSource but as we also need a control to allow the user to page trough the data it is easier to also add the DataPager control. Now you have the option of setting the PageSize on the DomainDataSource or the DataPager. I found that setting it on either would work just was well except for the initial load where the DataPager shows page 0 when the PageSize is set on the DomainDataSource while it is set to 1, the correct value, when set on the DataPager. I assume this is just a small bug in the current preview.

Another thing you can specify is the LoadSize. This determines how many rows are loaded with each request and if not set equals the PageSize. Setting this to double the PageSize will improve the responsiveness of the the client application so might be a good idea if the data isn’t too large.

    <UserControl xmlns:dataControls="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data.DataForm"  x:Class="LOBUsingRIAServices.CustomerListPage"

                 xmlns:data="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data"  

                 xmlns:riaControls="clr-namespace:System.Windows.Controls;assembly=System.Windows.Ria.Controls"

                 xmlns:web="clr-namespace:LOBUsingRIAServices.Web"

                 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 

                 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

        <Grid x:Name="LayoutRoot" Background="White">

            <riaControls:DomainDataSource x:Name="CustomerDataSource"

                                          LoadMethodName="LoadCustomers"

                                          LoadSize="40">

                <riaControls:DomainDataSource.DomainContext>

                    <web:NorthwindContext />

                </riaControls:DomainDataSource.DomainContext>

            </riaControls:DomainDataSource>

            <data:DataGrid ItemsSource="{Binding Data, ElementName=CustomerDataSource}" />

            <dataControls:DataPager Source="{Binding Data, ElementName=CustomerDataSource}" 

                                    PageSize="20" />

        </Grid>

    </UserControl>

The DataPager control is quite easy to use as well. Just drop it below the DataGrid and point it to the DomainDataSource to use and it just works. One problem I ran into was adding the DataPager above the DataGrid though. When I did that the DataPager didn’t show up on the UI so the user could not page through the data even though it still limited the data to the first page.

Using progressive loading

Another nice option is delayed loading. When using progressive loading all you need to do is specify the LoadSize on the DomainDataSource. The DomainDataSource will now load the specified number of rows, wait a bit and load the next set of rows. It will keep on doing this until all data is loaded. The nice thing here is that all the data is loaded but the UI still stays responsive for the user. De the default interval between load requests is 0.75 seconds but this can be fine tuned using the LoadDelay time span on the DomainDataSource.

    <UserControl xmlns:dataControls="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data.DataForm"  x:Class="LOBUsingRIAServices.CustomerListPage"

                 xmlns:data="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data"  

                 xmlns:riaControls="clr-namespace:System.Windows.Controls;assembly=System.Windows.Ria.Controls"

                 xmlns:web="clr-namespace:LOBUsingRIAServices.Web"

                 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 

                 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

        <Grid x:Name="LayoutRoot" Background="White">

            <riaControls:DomainDataSource x:Name="CustomerDataSource"

                                          LoadMethodName="LoadCustomers"

                                          LoadSize="10"

                                          LoadDelay="0:0:0.25">

                <riaControls:DomainDataSource.DomainContext>

                    <web:NorthwindContext />

                </riaControls:DomainDataSource.DomainContext>

            </riaControls:DomainDataSource>

            <data:DataGrid ItemsSource="{Binding Data, ElementName=CustomerDataSource}" />

        </Grid>

    </UserControl>

And all of this was done without writing any code add everything was completely declarative. Of course it is just a matter of setting properties so doing so from code is easy enough.

Enjoy!

Using Model – View – ViewModel with Silverlight

Maurice — Tue, 07 Apr 2009 14:23:46 GMT

The View – Model – ViewModel design pattern, also known as MVVM, is getting more popular these days. I have found it extremely easy to use when developing very different applications and have used the design pattern recently in both ASP.NET, WPF and Silverlight applications. However easy as it might be is seems to confuse people as I have seen some terrible examples where people make a complete mess of things.

Josh Smith did an excellent screen cast for Pixel8 on using MVVM with WPF, you can find it here.

Even thought the UI technology used doesn't change the basic MVVM pattern there are some subtle differences, like not easily being able to use ICommand in Silverlight, so I decided to create a small Silverlight sample.

The basic structure goes like this:

The user interacts with a View, implemented as a Silverlight user control.
The View is data bound to a ViewModel. This is the most important step to remember. The ViewModel is just another class.
The ViewModel is a wrapper for a Model. Think of the Model as the data and the business rules.

The Model

The Model I am using is very simple and has two read-write properties, FirstName and LastName, and a single read-only property, FullName. The FullName property represents some business rule on how a name should be formatted. I know it is a bit of a lame business rule but it is just a sample . The Model also implements INotifyPropertyChanged so the UI can be updated whenever a value is updated. The complete model looks like this:

        1: using System.ComponentModel;

       2:  

       3: namespace SilverlightMVVMDemo.Model

       4: {

       5:     public class Customer : INotifyPropertyChanged

       6:     {

       7:         private string _firstName;

       8:         private string _lastName;

       9:  

        public string FirstName

        {

            get { return _firstName; }

            set

            {

                _firstName = value;

                OnPropertyChanged("FirstName");

                OnPropertyChanged("FullName");

            }

        }

        public string LastName

        {

            get { return _lastName; }

            set

            {

                _lastName = value;

                OnPropertyChanged("LastName");

                OnPropertyChanged("FullName");

            }

        }

  

  

        public string FullName

        {

            get { return FirstName + " " + LastName; }

        }

  

        public event PropertyChangedEventHandler PropertyChanged;

  

        protected void OnPropertyChanged(string propertyName)

        {

            if (PropertyChanged != null)

            {

                var args = new PropertyChangedEventArgs(propertyName);

                PropertyChanged(this, args);

            }

        }

    }

}

The View

The View is just a Silverlight user control that makes things visible for the user. All controls use data binding to get to their values. There is one interesting twist here. Just like I had a business rule about how to format a FullName I have a rule about the font weight to use to display the FullName. This is just UI so not a business rule and as a result it is not stored in the Model. We do not want to code this in the UI as that makes things hard to test. So that leaves one place, the ViewModel . And the View uses data binding to set the FontWeight property.

The complete View looks like this:

       1: <UserControl

       2:     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 

       3:     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 

       4:     xmlns:SilverlightMVVMDemo_ViewModel="clr-namespace:SilverlightMVVMDemo.ViewModel" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" x:Class="SilverlightMVVMDemo.View.CustomerView" 

       5:     Width="400" Height="300" mc:Ignorable="d">

       6:     <Grid x:Name="LayoutRoot" 

       7:           Background="White">

       8:         <Grid.RowDefinitions>

       9:             <RowDefinition Height="0.133*"/>

            <RowDefinition Height="0.133*"/>

            <RowDefinition Height="0.133*"/>

            <RowDefinition Height="0.18*"/>

            <RowDefinition Height="0.42*"/>

        </Grid.RowDefinitions>

        <Grid.ColumnDefinitions>

            <ColumnDefinition Width="0.3*"/>

            <ColumnDefinition Width="0.7*"/>

        </Grid.ColumnDefinitions>

        <TextBlock Text="Firstname:" 

                   Margin="8"/>

        <TextBox Text="{Binding Path=FirstName, Mode=TwoWay}" 

                 Grid.Column="1" 

                 Margin="8,8,8,8"/>

        <TextBlock Text="Lastname:" 

                   Grid.Row="1" 

                   Margin="8"/>

        <TextBox Text="{Binding Path=LastName, Mode=TwoWay}" 

                 Grid.Row="1" 

                 Grid.Column="1" 

                 Margin="8,8,8,8"/>

        <TextBlock Text="Fullname:" 

                   Grid.Row="2" 

                   Margin="8"/>

        <TextBox Text="{Binding Path=FullName}" 

                 Grid.Row="2" 

                 Grid.Column="1" 

                 Margin="8,8,8,8"

                 FontWeight="{Binding Path=FullNameFontWeight}"

                 IsReadOnly="True"/>

        <Button Content="Save"

                Click="Button_Click"

                Grid.Row="3" 

                Grid.Column="1" />

    </Grid>

</UserControl>

The code behind is very simple and looks like this:

       1: using System.Windows.Controls;

       2: using SilverlightMVVMDemo.ViewModel;

       3:  

       4: namespace SilverlightMVVMDemo.View

       5: {

       6:     public partial class CustomerView : UserControl

       7:     {

       8:         public CustomerView()

       9:         {

      10:             InitializeComponent();

      11:             DataContext = new CustomerViewModel();

      12:         }

      13:  

      14:         private void Button_Click(object sender, System.Windows.RoutedEventArgs e)

      15:         {

      16:             var viewModel = (CustomerViewModel)DataContext;

      17:             viewModel.Save();

      18:         }

      19:     }

      20: }

In an ideal world there would be no code at all, or only that setting the DataContext but as Silverlight makes it a little harder to use commands there is a single line, okay two counting the cast, to pass the save command on to the ViewModel.

The ViewModel

The ViewModel class is the one that glues the View and the Model together, hence its name . basically the ViewModel wraps each Model object, so if you want to use a collection of customer models you create a collection of CustomerViewModel objects and databind against them. The ViewModel catches all PropertyChanged events from the Model and passes them on to the user interface. Whenever the FullName property changes the FullNameFontWeight might also change so in that case an extra PropertyChanged event is raised. Note that calculation of the FontWeight to use is part of the ViewModel as the UI depends on this but it is not a business rule per se.

Another example of a property like this would be the CSS class to use in an ASP.NET application. basically if a UI property changes, create a property get to do so and databind it.

The complete ViewModel class looks like this:

       1: using System.ComponentModel;

       2: using System.Windows;

       3: using SilverlightMVVMDemo.Model;

       4:  

       5: namespace SilverlightMVVMDemo.ViewModel

       6: {

       7:     public class CustomerViewModel : INotifyPropertyChanged

       8:     {

       9:         private Customer _model;

  

        public CustomerViewModel()

        {

            Model = new Customer() { FirstName = "Maurice", LastName = "de Beijer" };

        }

  

        public CustomerViewModel(Customer model)

        {

            Model = model;

        }

  

  

        public Customer Model

        {

            get { return _model; }

            private set

            {

                if (_model != null)

                    _model.PropertyChanged -= ModelPropertyChanged;

  

                _model = value;

  

                if (_model != null)

                    _model.PropertyChanged += ModelPropertyChanged;

            }

        }

  

        void ModelPropertyChanged(object sender, PropertyChangedEventArgs e)

        {

            OnPropertyChanged(e.PropertyName);

  

            if (e.PropertyName == "FullName")

                OnPropertyChanged("FullNameFontWeight");

        }

  

  

        public string FirstName

        {

            get { return Model.FirstName; }

            set { Model.FirstName = value; }

        }

        public string LastName

        {

            get { return Model.LastName; }

            set { Model.LastName = value; }

        }

  

        public string FullName

        {

            get { return Model.FullName; }

        }

  

        public FontWeight FullNameFontWeight

        {

            get

            {

                if (FullName.Length > 20)

                    return FontWeights.ExtraBold;

                else if (FullName.Length > 15)

                    return FontWeights.Bold;

                else if (FullName.Length > 10)

                    return FontWeights.Normal;

                else

                    return FontWeights.Light;

            }

        }

  

        public event PropertyChangedEventHandler PropertyChanged;

  

        protected void OnPropertyChanged(string propertyName)

        {

            if (PropertyChanged != null)

            {

                var args = new PropertyChangedEventArgs(propertyName);

                PropertyChanged(this, args);

            }

        }

  

        internal void Save()

        {

            // Implement the logic to save the customer.

        }

    }

}

In this case I duplicated all properties from the Model in the ViewModel. This is not a must, some people prefer to expose and bind to the Model directly. It saves a few lines of code but I prefer not to do so. Of course there is no need to duplicate properties the UI is never going to bind to directly.

Model-View-ViewModel guidelines

Not very difficult at all as long as you keep to a few guidelines:

Never set any UI properties from your CS code with the exception of the DataContext.
If you need an event handler in your code behind, like the button click, make it a single line and pass the request onto the ViewModel.
All UI control properties that need to change at runtime do so by data binding to a ViewModel property.
Organize your ViewModel types per View and not per Model. It is perfectly fine to create a ViewModel that wraps two different Models. A View has only a single DataContext so you cannot bind it to multiple ViewModel objects.

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

And now on Twitter at http://twitter.com/mauricedb.

Want to download all MIX sessions?

Maurice — Tue, 31 Mar 2009 06:52:40 GMT

Then you should check Mike Swanson’s blog post here. He has two batch files, the first downloads all MIX session recordings with in the format you like, the second renames them so it is easier to make sense of all the media file names.

If you just want a list of all sessions with download links this page might be the thing for you.

So much better than downloading them by hand. Not as good as going to the MIX itself but if you, like me, couldn’t go it is still a nice way to see all the content.

Enjoy!

Visual Basic QuickStarts and How-to Topics for the Composite Application Guidance for WPF and Silverlight

Maurice — Wed, 25 Mar 2009 08:12:57 GMT

The P&P team have just release a VB version of the Prism quick starts.

You can download the goods here.

Enjoy!

Samples and PowerPoint from my WCF talk

Maurice — Wed, 11 Mar 2009 04:25:00 GMT

Attached is are the samples and slides I used for my intro into WCF talk yesterday at the VB Central meeting in the Netherlands.

Download samples

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Now also on twitter at http://twitter.com/mauricedb

Using a TransactionScopeActivity with a WCF ReceiveActivity revisited

Maurice — Tue, 10 Mar 2009 12:42:15 GMT

Last year Marcel and I worked on a problem using a TransactionScopeActivity inside a WCF ReceiveActivity. I blogged a number of time about our finding, for example here.

Last week I heard from Marcel that a hotfix was finally available that solves this problem. He blogged about it here. Great work to see there is a fix for this serious problem.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

And now on Twitter at http://twitter.com/mauricedb.

Looking back at the MVP Summit

Maurice — Sat, 07 Mar 2009 11:08:09 GMT

Last week lots of MVP, myself included, where in Redmond visiting Microsoft on our yearly MVP pilgrimage. The MVP Summit is always a great event. Not only do we get to talk to the MS team members who actually design and build all the software we love and use but we also get to meet each other. And with MVP’s being located around the world that is kind of rare as well.

Despite this being a great event I still have very mixed feelings about this last MVP summit. The problem isn’t the events itself or the people I met, that was al great . No the problem was in some of the technological decisions made in product groups. Unfortunately I can’t divulge details yet because I have signed an NDA but as soon .NET 4.0 as beta 1 is made public I will be able to blog about some of these decisions. And rest assured I will!

The reason we really need to is the way these important changes are communicated. Or should I say not communicated. Some very important changes where not communicated at all and could only be derived by bullet points missing from PowerPoint slides. Only when directly asked about the missing bullet point would someone say “Yes that is right, we decided to …. NDA … because … NDA …”. Sorry about the NDA part .

I can only say that these decisions are a big problem and I know several MVP’s who decided to skip other sessions on the same product as a result. I didn’t, as far as I am concerned ignoring a problem is not going to make it go away, but I really think this product team needs to reevaluate this decision and the general future trend.

Despite this hiccup I am very exited about lots of the things I got to see and am really looking forward to .NET 4 and Visual Studio 2010. Now if we only could have a beta today . When we will have a first beta is still a big question though. If a date was announced I missed it, the best I heard was a quarter and is quite a time span.

Enjoy.

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

SilverUnit - Unit testing framework for Silverlight

Maurice — Wed, 25 Feb 2009 08:11:13 GMT

Roy Osherove has just released SilverUnit, a unit testing framework for Silverlight code. I haven't tried this yet but it certainly looks really interesting as you can start running your Silverlight unit tests inside of MS Test or NUnit.

And kind cool to hear this is written in VB

You can find more information and download SilverUnit from CodePlex here.

Enjoy!

www.TheProblemSolver.nl
Wiki.WindowsWorkflowFoundation.eu

Patterns & Practices release Prism version 2

Maurice — Wed, 18 Feb 2009 19:01:01 GMT

The Patterns & Practices group at Microsoft have just released Prism version 2. I am pretty exited about this because Prism version 2 supports both WPF and Silverlight. And as it makes extensive use of the Model - View - ViewModel amongst other design patterns it is a great place to learn, even if you don't use it as is.

Check out the main "Composite Application Guidance for WPF and Silverlight" page here. Or read Blaine Wastell about it here.

Enjoy!