- Posted by Peter Himschoot on July 11, 2010
Visual Studio 2010 now comes packed with too many assemblies. The list of assemblies to pick from in the Add Reference dialog is now a little too large for my taste. Today, while browsing around in the Visual Studio 2010 Extension Manager, I found the Search References extension:
After installing it my Add Reference dialog now looks like this:
And typing in the search box instantly filters the list of assemblies. Nice. Microsoft should have provided this out of the box! It is also a nice sample of how extensible Visual Studio is.
- Posted by Peter Himschoot on May 11, 2010
This week I got a question whether it is still possible to keep some file checked-out during a check-in. This is something you can do with Source Safe for example. To be honest I had no idea if this is possible, so I decided to have a look. So the answer is yes (although in general I think this is dangerous because this way people tend to check out files for long periods…).
Simply go to options and check the fourth check-box from the top.
- Posted by Peter Himschoot on April 9, 2010
I’m currently experimenting with Pex, Moles and Code Contracts, and I wondered what effect code contracts have on Pex tests. So I build this simple piece of code:
1: public class Demo
2: {
3: public int Foo(int a, int b)
4: {
5: if (a < 0)
6: return a;
7: else if (a > 0)
8: return b;
9: else
10: return a + b;
11: }
12: }
Then I make Pex generate its Parameterized Unit Tests (PUTs). This generates the following test:
1: [PexClass(typeof(Demo))]
2: [PexAllowedExceptionFromTypeUnderTest(typeof(InvalidOperationException))]
3: [PexAllowedExceptionFromTypeUnderTest(typeof(ArgumentException), AcceptExceptionSubtypes = true)]
4: [TestClass]
5: public partial class DemoTests
6: {
7: /// <summary>Test stub for Foo(Int32, Int32)</summary>
8: [PexMethod]
9: public int Foo(
10: [PexAssumeUnderTest]Demo target,
11: int a,
12: int b
13: )
14: {
15: int result = target.Foo(a, b);
16: return result;
17: // TODO: add assertions to method DemoTests.Foo(Demo, Int32, Int32)
18: }
19: }
I just leave the code, right-click on The Foo method of the DemoTests class, choose “Run Pex explorations” and I get this:
As you can see the exploration calls my code with negative, zero and positive values. What happens when I add a contract stating that a should be positive?
1: public class Demo
2: {
3: public int Foo(int a, int b)
4: {
5: Contract.Requires(a > 0);
6: if (a < 0)
7: return a;
8: else if (a > 0)
9: return b;
10: else
11: return a + b;
12: }
13: }
Only line 5 was added, but if I run the pex explorations again I get:
The effect is that Pex now doesn’t explore negative numbers, because it can deduce from the contract not to even try.
What if I use a contract to state that b should be negative?
1: Contract.Requires(b < 0);
Again Pex sees this and explores my code with negative b:
One more. When I change my code to do a little more with b, like this:
1: public int Foo(int a, int b)
2: {
3: Contract.Requires(a > 0);
4: Contract.Requires(b < 0 || b > 10);
5: if (a < 0)
6: return a;
7: else if (a > 0)
8: {
9: if (b > a)
10: return a;
11: else
12: return b;
13: }
14: else
15: return a + b;
16: }
and when I run the explorations again:
So, you can guide Pex by supplying contracts on the arguments of your methods.
- Posted by Peter Himschoot on April 8, 2010
Co and contra-variance were introduced to VB.NET and C# to make working with certain classes more natural (“because it should work”). But beware, I was experimenting a bit with this and found following possible breaking change. I started with these two classes:
C#
1: public class Person
2: {
3: // ...
4: }
5:
6: public class Vip : Person
7: {
8: // ...
9: }
VB.NET
1: Public Class Person
2: '
3: End Class
4:
5: Public Class Vip
6: Inherits Person
7: '
8: End Class
Then I added a collection of people:
C#
1: public class PersonList
2: {
3: public void Add(object obj) {
4: // ...
5: }
6:
7: public void Add(Person p)
8: {
9: // ...
10: }
11:
12: public void Add(IEnumerable<Person> people)
13: {
14: foreach (Person p in people)
15: {
16: // ...
17: }
18: }
19: }
VB.NET
1: Public Class PersonList
2: Public Sub Add(ByVal obj As Object)
3: '
4: End Sub
5:
6: Public Sub Add(ByVal person As Person)
7: '
8: End Sub
9:
10: Public Sub Add(ByVal list As IEnumerable(Of Person))
11: '
12: End Sub
13: End Class
Next I create a PersonList collection and then add a list of Vip’s:
C#
1: class Program
2: {
3: static void Main(string[] args)
4: {
5: PersonList people = new PersonList();
6:
7: List<Vip> others = new List<Vip> {
8: new Vip(), new Vip()
9: };
10:
11: people.Add(others);
12: }
13: }
VB.NET
1: Sub Main()
2: Dim people As New PersonList
3: Dim others As New List(Of Vip)(New Vip() {New Vip(), New Vip()})
4: people.Add(others)
5: End Sub
When I compile this in Visual Studio 2008 the first Add method, taking the object argument, gets called.
But with Visual Studio 2010 (using the .NET 4 target) the third Add method gets called. This is because now IEnumerable<T> is co-variant and will now convert the List<Vip> to an IEnumerable<Person>.
Ok, granted. This is NOT something you will see every day, but if you ever encounter it, this might be very confusing.
This kind of problem can also occur with extension methods and user-defined conversions…
- Posted by Peter Himschoot on March 29, 2010
This blog post accompanies my session on Workflow Foundation 4 programming during the Belgian Tech Days (actually developers and IT-pro days :)). During this session I built a WCF service using Workflow Foundation 4, and I want to show you how to do this on your own…
In the first part you’ll learn how to create a simple FlowChart workflow and test it, and then in the second part you’ll learn how to setup correlation so multiple players can play the game…
Preparing the lab
This lab starts with a new project, so start Visual Studio 2010 and create a new workflow service project (call it NumberGuessingGame):
This creates a new solution with a workflow project.
Remove Service1.xamlx, we’re going to add a new service with a better name.
Right-click the project and add a new item. Select the WCF Workflow Service template and name it GuessIt.xamlx.
Creating the initial FlowChart
This adds a workflow service with a sequential activity containing a Receive and Send activity. Delete the sequential activity leaving the workflow empty. Open the toolbox and drag a FlowChart activity onto the workflow designer. This should look like this now:
Next drag a Receive activity onto the designer, below Start. Name it Start A New Game. Select the receive activity and enter following the OperationName, ServiceContractName and CanCreateInstance properties in the properties window:
Next right-click on the receive activity and select the Create SendReply option from the drop-down menu. This add a Send activity to the workflow. The Send is coupled to the receive activity through its Request property:
Now connect the activities:
Adding variables
Now, in the workflow designer open the variables window and add a new variable called player of type String. This will hold the player name received through the “Start A New Game” Receive activity. You will also see a variable of type CorrelationHandle. This is used to connect several receive and send activities through correlation. Rename this to gameHandle.We’ll use this handle later to setup content-based correlation.
Now add two new variables theNumber and guess, both of type Int32. The first is the number the user needs to guess, to you need to initialize it to a random number between 0 and 100. Use the Random type to do this:
Go back to the first receive activity. Click on the content property. This opens the Content Definition window. Select the player as the message data (and set the Message type to String):
Do the same for the send activity, but now use following expression (of type String):
1: player + " guess the number between 0 and 100"
You might also get validation errors because you renamed the correlation handle to gameHandle. Change the CorrelationInitilizers property to use gameHandle (click on the … button).
Testing the service
Press F5 in Visual Studio. The WCF Test Client will start and automatically fetch meta-data from the service. Double click the Begin method. This opens a new tab allowing you to invoke the Begin operation on the service. Enter your name and click Invoke. In the bottom area you should see the result of invoking the begin method.
This concludes the first step.
Adding the data contracts
Let’s add a couple of data contracts to the project, one for a game and another for a guess. Note that both contain the player name, this way our service will be able to distinguish between multiple games, as long as each player uses a unique player name:
1: [DataContract]
2:
3: public class Game
4:
5: {
6:
7: [DataMember]
8:
9: public string PlayerName { get; set; }
10:
11: [DataMember]
12:
13: public string Message { get; set; }
14:
15: }
16:
17: [DataContract]
18:
19: public class Guess
20:
21: {
22:
23: [DataMember(IsRequired = true)]
24:
25: public string PlayerName { get; set; }
26:
27: [DataMember(IsRequired = true)]
28:
29: public int Try { get; set; }
30:
31: }
Make the “Send Game Started” send activity use a Game instance as the result. To do this you will need to add another variable of type Game, and initialize it to a new instance:
Now add to assign activities after the Begin receive activity, and assign appropriate values to the game:
Adding the guessing logic
Add another variable, calling it guess of type Guess. Then add another receive activity after the send activity, but now with an operation name called Guess, taking guess variable as its content. Check if the guess was right using a decision shape. If so, congratulate the user. If not, decide whether the guess was too small or large. Confirm this back to the user using three SendReply activities (create each one by right-clicking the Guess receive activity and select Create SendReply).
Here is an example of the result:
Adding Content-based Correlation
Of course we want to make a single player play the same game, but what if multiple players are playing on the same server? We need correlation. In this part we’re going to correlate the guess activity to the Begin activity using the player’s name. That is why our data contract both contain the player’s name (by coincidence the properties have the same name, but this is not required).
To do correlation we need a correlation handle. This handle will act like a key to a workflow. If a request comes in, we’re going to find this key through part of the message, in our case the player’s name. So, if you haven’t done so, add a new variable to the workflow called gameHandle of type CorrelationHandle. The make sure that all the first sendReply activity is set to initialize this handle by ensuring the CorrelationInitializer is set like this:
When the workflow sends this message, we’re saying that the key of the gameHandle is the player’s name. So when another message arrives, the workflow runtime can then see is the message contains a valid key (again the player’s name), use this key to find the right workflow instance, and then send the message to it. So next step is to set the Guess receive activity’s Correlates On like this:
Now you should be able to play a game, making sure that the first and following messages all have the same player name. You can also start two or more games, each with their own player name!
- Posted by Peter Himschoot on March 22, 2010
ObservableCollection<T> is a generic collection added as part of WPF and Silverlight. WinForms has BindingList<T>. So writing code that targets both WinForms and WPF would mean using BindingList<T> (the common thing) and writing code targetting WPF and Silverlight would mean ObservableCollection<T>. So there would be no way to write code that targets all three platforms. Luckily now (in .NET 4) we can use ObservableCollection<T> anywhere because Microsoft made it part of System.dll. Nice! Two others were also moved here: ReadOnlyObservableCollection<T> and INotifyCollectionChanged.
To double check if I could use these collections outside WPF projects I created a simple console application using them:
1: class Program
2: {
3: static void Main(string[] args)
4: {
5: ObservableCollection<string> noWpf = new ObservableCollection<string> { "Hello", "World" };
6: INotifyCollectionChanged watchCollection = noWpf as INotifyCollectionChanged;
7:
8:
9:
10: if (watchCollection != null)
11: {
12: watchCollection.CollectionChanged += (sender, e) => { Console.WriteLine("Collection action = {0}", e.Action); };
13: }
14:
15: noWpf.Add("Love it!");
16: }
17: }
Compiles. Runs.
Could I use it in WinForms? So I created a simple WinForms application like this:
1: public partial class Form1 : Form
2: {
3: ObservableCollection<string> noWpf;
4:
5: public Form1()
6: {
7: InitializeComponent();
8:
9: noWpf = new ObservableCollection<string> { "Hello", "World" };
10: var bs = new BindingSource() { DataSource = noWpf };
11: bs.ListChanged += (sender, e) => { MessageBox.Show(e.ListChangedType.ToString()); };
12: listBox1.DataSource = bs;
13: }
14:
15: private void button1_Click(object sender, EventArgs e)
16: {
17: noWpf.Add("Test");
18: }
19: }
But when I click the button, which adds a new element to the observable collection, the listbox doesn’t update. It looks like winforms databinding doesn’t support ObservableCollection…
- Posted by Peter Himschoot on March 18, 2010
Configuring your services
Normally I configure my services using Visual Studio (and type-ing in the configuration as Xml) or using the WCF Service Configuration tool. AppFabric also allows you to configure your services, directly from IIS (making it a nice integrated experience!). The difference is in that AppFabric exposes the stuff an it-pro needs to look at the health of an application more… Developers are more interested in making it work, productions is more interested in keeping it working… <grin>
You can setup a persistance and tracking store (actually databases) to make your services trackable and durable. This will also make it easier (or less hard) to see why your service is no longer functioning the way it should. Of course you can still setup the System.Diagnostics tracing, but this again is more for developers.
Some preparations are needed
AppFabric uses the net.pipe protocol to manage your services (through standard endpoints), so you might need to enable this on IIS. Select your site, then select Edit Bindings…
The following window should open:
If net.pipe is not listed, hit the Add… button and select net.pipe. Use * for Binding information.
Then go to your service and select Advanced Settings… The dialog should open:
Add net.pipe to the list of Enabled Protocols.
You might also need to run the AppFabric system-level configuration. To do this, go to Start->All Programs->Windows Server AppFabric->Configure AppFabric. The configuration utility should launch:
Hit Next:
Here you can configure the monitoring and persistance databases. Check the Set Monitoring configuration check-box, select the account you want to use and the provider (there is one default, which will store everything in a SQL server database:
Hit the Configure… button. Configure as follows (replacing Peter-PC with your domain/machine name):
Hit Ok. Check the results. You might get an ‘the database already exists’ kind of warning. Simply continue…
Continue through the wizard…
Configuring a WCF service
In IIS, select your site or service (and most of this can also be done at other levels), and then in the actions pane select “Manage WCF and WF Service->Configure…”
This opens the “Configure WCF and WF for Site” dialog:
Check the “Enable metadata over HTTP” to set the ServiceMetadata behavior.
Over to the Monitoring tab:
Keep the checkbox checked if you want monitoring records written to the monitoring database. Using the level you can change from monitoring everything to nothing…
You can also configure the usual WCF tracing and message logging here.
The throttling tab allows you to limit the number of requests and service instances, while the security tab allows you to set/change the service certificate.
A later post will be about configuring WCF and Workflow services…
- Posted by Peter Himschoot on March 13, 2010
Microsoft released Visual Studio 2010 RC a while ago, but unfortunately this broke Windows Server AppFabric beta 1. Luckily march 1 MS released beta 2, which works with VS 2010 RC. I’ve installed it and will now try to show you a couple of things.
So what is AppFabric? To be honest, there is another AppFabric, the one for Azure, and that is not the one I am talking about.
What is Windows Server AppFabric?
AppFabric makes installing, administering, monitoring and fixing problems in WCF 4 (!Yes, only starting at .NET 4) services a lot easier by extending IIS and WAS (Windows Activation Services, which are used to host non-HTTP WCF services in IIS). It also adds a distributed caching mechanism (also known as Project Velocity) to make it easier to scale ASP.NET and WCF services. If you’re familiar with BizTalk 2006/2009, you’ll know that the BizTalk Administration application shows you each BizTalk application’s health, what went wrong, how many were executed, etc… AppFabric gives you the same but now for WCF and WF 4 services.
Look at this screen shot:
As you can see, after installing AppFabric IIS is now showing these new icons: AppFabric Dashboard, Endpoints and Services. The dashboard will show you the current status of your services (running, stopped, with errors, etc…). Endpoints and Services allow you to list and configure the endpoints and services.
Deploying using AppFabric
AppFabric Hosting Services provides easier deployment of services:
First thing you need to do is to package your WCF service. To do this go to the project properties and select the new Package/Publish tab:
You can now select where to create the package (and if your want it as a .zip file) and how to deploy it in IIS.
Now you need to create the deployment package in Visual Studio 2010:
Now we can import the application using IIS:
This will open the Import Application Package dialog. Use the browse button to open the package .zip file:
Hit next:
And Next again:
Note that the service name is taken from the package properties. Hit next again, hopefully your services will deploy successfully.
To verify this, you can go to your site in IIS:
And click on Services. You should see your service listed (for example I have three services running here):
You can also click on Endpoints to see the list of endpoints:
Because of WCF default endpoints you get 4 different endpoints per service; you can modify which types of default endpoints you want, but that is now what I’ll be showing you here.
A note on using your own application pool with AppFabric
During my experiments I created a new AppPool for my services. When testing my service, I would always get the following error:
HTTP Error 503. The service is unavailable.
First I thought the solution would be easy. My application pool was stopped. Starting it should fix the problem. But it didn’t.
So I investigated a little further. Seems that my new application pool tries to use .NET 4 version 21006 (beta 2?). I could see this in the Event Viewer:
The worker process failed to pre-load .Net Runtime version v4.0.21006.
I think something didn’t (un)install during my migration to .NET 4 RC. So I’m now using the ASP.NET 4 application pool…
- Posted by Peter Himschoot on March 3, 2010
Team System 2010 introduces the concept of team project collections (TPC). A team project collection is, as it says, a collection of team projects, which can be managed individually. You can backup, move, delete, etc… each collection individually. Each collection will also have its unique work item ids, check sets, etc… Team project collections also change the way team foundation stores its stuff. Before it would use a bunch of databases, now everything connected is stored in a single database. One database per collection. You can easily find the database because it’s called Tfs_<CollectionName>. You ‘ll also find the Tfs_Configuration database containing all configured project collections (and depending on your installation a database for the analysis services).:
Project collections also solve a problem some of you might have encountered; TFS 2008 has an upper limit of 255 team projects. Now with TPC you just add another TPC when you reach the limit (I don’t know the limit of projects per collection, but I would assume it would be around the same…).
A TPC can also easily be moved to another team server/farm, or to another SQL server on the same farm, as long as you keep it on the same type of SQL server (enterprise, express, …). Documentation states you cannot move it to another kind. The way to do this is to first open the Team Foundation Administration Console, and select the Team Projects Collections tree item. To the right you should see all your TPCs.
Here you can also create new TPC's, but that should be obvious.
So to move a TPC you should first stop the collection. You’ll be asked for a reason:
And then you detach the collection:
Next you go through a verification step:
And then you click Complete:
Now the TPC is no longer connected to TFS, but is still there in SQL server.
So now you detach the database in SQL server, move it to another SQL server or TFS farm. You might first need to restart a couple of services, such as the build service.
So after attaching the database in SQL server, we now need to attach the database to TFS; go back to Team Foundation Administration Console, and click the “Attach Collection” button. Now choose your SQL server instance, and you’ll see all candidate databases:
Hit Next if you want to change properties such as the name/description:
And next again to see an overview.
So complete attaching, hit Verify to make sure everything is in order:
And then hit attach.
Eh voila!
Now the TPC should be in the list:
You can also split the projects in a single TPC to multiple TPCs (but not merge them, so be careful), but that will be for a later post.
- Posted by Peter Himschoot on February 28, 2010
In this blog post I want to talk about .NET 4 new Lazy<T> class. First of all, why would you need something called Lazy?
You can use it for data access for example; when you load a row from a database parent table. Would you need to load the child rows automatically, or delay until they’re required. Some systems will delay load automatically, or load all they can (but what then when the child rows have other relations to grandchild rows, etc…). This kind of delayed loading of data is just what Lazy<T> (or Lazy(Of T) when using VB.NET) supports.
It’s a great type to use when you have an object which is very expensive to create, and you only want to create it on first use.
Let’s start with an example; let’s say you have this big-ass class:
1: class BigAndExpensive
2: {
3: string s = "";
4:
5: public string GetTheData()
6: {
7: return s;
8: }
9:
10: public BigAndExpensive()
11: {
12: Console.WriteLine("BigAndExpensive is being created...");
13: for (int i = 0; i < 10000; i++)
14: s = s + ".";
15: Console.WriteLine("BigAndExpensive is finally created...");
16: }
17: }
As you can see, creating is very expensive (it will actually consume about 10 Gb of memory, triggering a lot of garbace collects).
Let’s create an instance of this class without, then with Lazy<T> and look at the performance:
1: BigAndExpensive be;
2: Lazy<BigAndExpensive> lbe;
3:
4: using (new MeasureDuration("Not using Lazy evaluation"))
5: {
6: be = new BigAndExpensive();
7: }
8: using (new MeasureDuration("Accessing non-lazy object's method"))
9: {
10: string s = be.GetTheData();
11: }
12: using (new MeasureDuration("Using Lazy evaluation"))
13: {
14: lbe = new Lazy<BigAndExpensive>(false);
15: }
16: using (new MeasureDuration("Accessing lazy object's method"))
17: {
18: string s = lbe.Value.GetTheData();
19: }
20: using (new MeasureDuration("Again accessing lazy object's method"))
21: {
22: string s = lbe.Value.GetTheData();
23: }
In order to use the Lazy<T> object you have to get it’s value property. When the lazy loaded value hasn’t yet been created, accessing the Value will create it.
The MeasureDuration class is a little timer taking advantage of the using statement:
1: class MeasureDuration : IDisposable
2: {
3: Stopwatch sw;
4: string what;
5:
6: public MeasureDuration(string what)
7: {
8: this.what = what;
9: sw = new Stopwatch();
10: sw.Start();
11: }
12:
13: public void Dispose()
14: {
15: sw.Stop();
16: Console.WriteLine("Measured duration of -{0}- took {1} ticks ({2} ms)"
17: , what, sw.ElapsedTicks, sw.ElapsedMilliseconds);
18: }
19:
20: }
The output I get on machine looks like this:
As you can see, creating a Lazy object is very fast, but of course as you can expect, using it the first time is just as expensive due to the creating process. Using it the second time is again very fast.
Now go back to the code, and look for the Lazy<T> constructor. Change the false argument to true:
1: lbe = new Lazy<BigAndExpensive>(true);
This will make the instantiation process of the actual instance thread-safe. This means it will be a little slower, but only during construction. Is it worth the price? If you’re using multiple threads YES YES YES!
Now let’s try to see what happens when many threads access an unprotected Lazy object (never be lazy AND unprotected :))
This is the code:
1: private static void UsingLazyObjectsFromMultipleThreads()
2: {
3: Lazy<BigAndExpensive> createMeOncePlease = new Lazy<BigAndExpensive>(isThreadSafe:false);
4:
5: ManualResetEvent youMayBegin = new ManualResetEvent(false);
6: AutoResetEvent done = new AutoResetEvent(false);
7:
8: // create a lot of threads that will use our object all at once
9: for (int i = 0; i < 20; i++)
10: {
11: Thread t = new Thread(() =>
12: {
13: youMayBegin.WaitOne();
14: Console.WriteLine("Thread {0} getting data", Thread.CurrentThread.ManagedThreadId);
15: using (new MeasureDuration("Multithreading"))
16: createMeOncePlease.Value.GetTheData();
17: done.Set();
18: });
19: t.Start();
20: }
21: youMayBegin.Set();
22: // wait for all threads to complete
23: for (int i = 0; i < 20; i++)
24: done.WaitOne();
25:
26: }
I’ve now used the named argument feature of C# 4.0. In this case it make the code a lot clearer doesn’t it?
So what does the code do. It creates 20 threads which all first wait for the “youMayBegin” event. This way all threads will start running at the same time. Then they each access the “createMeOncePlease” lazy instance, so some of them will start to create the instance (because it hasn’t yet been created). Then they will all signal that they’re done so the main thread can stop too.
So let’s run the code (making sure the isThreadSafe is set to false). I get this:
This is bad. Very bad. Instead of calling the constructor of my very expensive object once, it calls it several times. why?
Think about lazy’s possible thread-unsafe implementation:
1: class Lazy<T> where T : class, new()
2: {
3: T instance = null;
4:
5: public T Value
6: {
7: get
8: {
9: if (instance == null)
10: instance = new T();
11: return instance;
12: }
13: }
14: }
When you run the if statement on multiple thread, each will evaluate to true, then each will create an object and overwrite instance’s value.
So what is the solution? Simply pass true for the isThreadSafe argument.
Running this code once more looks like this on my machine:
Good. My expensive object only get’s created once. But why are the calls soo expensive after all. That is because when we access Value, only one thread will be allowed to create the instance, but the other Value calls will need to wait for the first one to complete. If you insert another call using Value you’ll see the speed is very fast.
If you only need initialization to be thread-safe, or only access to the object in a thread-safe you you can also use the contructor taking a LazyThreadSafetyMode enumeration:
1: None = 0,
2: PublicationOnly = 1,
3: ExecutionAndPublication = 2
What if your expensive class requires special construction, like a special constructor? Then you can use another constructor of Lazy<T>, one that takes a delegate( Func<T> ) so you can create your object your way.
1: Lazy<BigAndExpensive> createMeOncePlease =
2: new Lazy<BigAndExpensive>(() => new BigAndExpensive());