Visual Studio 2012 RC: http://www.microsoft.com/visualstudio/11/en-us

Team Foundation Server 2012 RC: http://www.microsoft.com/en-us/download/details.aspx?id=29918

If you are interested in the changes from the Beta you can check this MSDN Page, you can find also a lot of information from the Visual Studio ALM Rangers, that released the Readiness RC Wave full of important information. We have a good improvement on the upgrade process as described in This post, that explains the new upgrade procedure and how the wizard can avoid breaking something if you have customized a standard TFS Process.

You have also a brand new Developer Tools Blog at this url: http://blogs.msdn.com/b/developer-tools/

Happy Programming.

Gian Maria

Figure 1: Standard form to connect to a TFS team project, after the installation of the hotfix to connect to TFS Preview

Now if you press “Sign Out” the standard login form of TFS Preview appears and it should prompt you for a new login, but sometimes it happens that the form automatically logins you again so you are not able to logout. This happens sometimes when You check the “log me automatically” checkbox, but now you are unable to change the user you are using to login to TFS Preview.

A simple workaround is open a Web Browser window (in menu View->other windows->Web Browser"), navigate to your TFS Preview web site xxxx.TfsPreview.com and you should be already logged with the same user you see in the “Connect to Team Project” window. Now you can simply logout from the site

Figure 2: Signout the current user from TFS Service web side from a Web Browser inside Visual Studio.

Now you are logged out and even if you are redirected to a page that tells you “Sign-out isn’t complete” you can just close all instances of Visual Studio, then, if you open again the “Connect to Team Project” dialog, you should now be prompted for login and you are finally able to change the TFS Preview Logged User

Gian Maria.

This is usually not a big problem, because you can query a collection using simple JSON-like query, but if you are used to standard LINQ provider, probably you will get a little bit lost on how to create the JSON query to retrieve the data you need. This is the scenario I need to solve: I have a stupid Winform that is able to show some information from a standard Log4Net Sql database (using the adonetappender) and I want to be able to use the very same interface to load data from mongo database. First of all I need to load all distinct value for the property level  and loggerName, because I have a combo where the user can filter for Severity (ERROR, WARN, INFO, Etc.) and a list of checkboxes used to filter for loggerName. Luckily enough, mongo offer such a functionality out of the box.

var db = server.GetDatabase(bsDatabase.Current as string);
var collection = db.GetCollection(bsCollections.CurrencyManager.Current as string);
var allLevel = collection.Distinct("level");

The code is really simple, I create a connection to the database and then retrieve a reference to collection that was selected in the interface from the user, then I use the Distinct() method of MongoCollection object, passing the name of the property you need, and Mongo gave you the distinct list of every value of that property. This permits me to populate the user interface with few lines of code.

Now it is time to think how to create a query to retrieve all the document with a certain level of logging and belonging to a list of possible loggerName. In my software I usually use Castle Log4net Integration, this means that loggerName property is equals to the name of the class that issue the log and usually the user wants to see logs belonging to one or more class, something like: all ERROR from classa or classb and severity ERROR. Mongo has a QueryBuilder helper class that makes easy to create such a query with a little help from intellisense and without the need to dirty your hand directly with JSON

var query = Query.And(
                    Query.EQ("level", "ERROR"),
                    Query.Or(
                        Query.EQ("loggerName", "classa"),
                        Query.EQ("loggerName", "classb")
                    )
                );

Now I need to make this code dynamic, because I need to create a query that retrieve logs belonging to an unknown number of loggerName, such as “classa”, “classb” and “classc”, because user interface contains a CheckBoxList of every loggerName present into the database, and the user can choose any number of elements to search from, so I need to dynamically create the list of condition to create a dynamic query.

List<IMongoQuery> mainQueries = new List<IMongoQuery>();
if (!String.IsNullOrWhiteSpace(cmbLevel.Text))
{
    mainQueries.Add(Query.EQ("level", cmbLevel.Text));
}
if (cbList.CheckedIndices.Count > 0)
{
    List<IMongoQuery> listOfLoggerNameQueries = new List<IMongoQuery>();

    foreach (Int32 index in cbList.CheckedIndices)
    {
        String value = cbList.Items[index].ToString();
        listOfLoggerNameQueries.Add(Query.EQ("loggerName", value));
    }
    mainQueries.Add(Query.Or(listOfLoggerNameQueries.ToArray()));
}
var finalQuery = Query.And(mainQueries.ToArray());

Code is really simple, because it simply create a list of IMongoQuery object that contains all the first-level condition that will be combined in the last instruction with the Query.And() helper. Since I can select more than one loggerName from the checkboxList I can simply iterate through all CheckedIndices and create a Query.EQ(“loggerName”, value) condition for every checked name in the UI, then I can combine all these condition with Query.Or() to produce a single IMongoQuery that is added to the main list.

After you have the query you can use to retrieve records.

var cursor = collection.Find(finalQuery);
Int32 limit;
if (!Int32.TryParse(txtLogNum.Text, out limit))
{
    limit = 50;
}
cursor.SetFields("level", "loggerName", "message", "exception", "customproperties", "timestamp");
cursor.SetSortOrder(SortBy.Descending("timestamp"));
cursor.Limit = limit;

Finally the method MongoCollection.Find() returns a cursor that actually does not contains any data,  you can now add Sorting, pagination and specify all the properties you want to return directly on the curso, and when you iterate through all element with a foreach data will be retrieved from the database. This is really similar to a LINQ query, where no data is retrieved if you call Where(), Select() etc, but only when you iterate the query or you call a not deferred operator like List().

With this simple code I’m able to build a simple form to have a quick visualization of all the logs stored inside a Mongo Database even if the appender store untyped objects.

Gian Maria.

To be able to automatically enable this feature on the Log4Net Mongo appender you need to do a little modification to the code, this is because the original code simply gets a reference to the collection with this code.

connection = MongoServer.Create(mongoConnectionString.ToString());
connection.Connect();
var db = connection.GetDatabase(DatabaseName);
collection = db.GetCollection(CollectionName);

C# drivers for Mongo automatically creates a collection if it is not present, this means that when you call db.GetCollection if the collection is not present it will be automatically created, but it is not capped. To solve this problem you can modify the initialization code with this code.

if (!db.CollectionExists(collectionName)) {
    var options =  CollectionOptions
        .SetCapped(true)
        .SetMaxSize(CappedSize);
    db.CreateCollection(collectionName, options);
}
collection = db.GetCollection(CollectionName);

MongoDb C# drivers has a class called CollectionOptions used to setup options to create a new MongoCollection and it can be accessed with a really easy Fluent-Interface, in my example I call SetCapped(true) to enable a capped collection and SetMaxSize() to setup the maximum size in bytes. The size of the capped-collection is stored in the appender property called CappedSize, the default is 500MB, but you can setup any size you likes in standard log4Net configuration.

Gian Maria.

System.ServiceModel.CommunicationException: The underlying connection was closed: A connection that was expected to be kept alive was closed by the server. —> System.Net.WebException: The underlying connection was closed: A connection that was expected to be kept alive was closed by the server. —> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. —> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host

This problem is usually caused by some error in the communication channel, but even in such a situation, enabling the trace listener immediately gave to you an idea of the problem.

Figure 1: How to identify the problem thanks to WCF Trace Listener

In my situation the error is ClientProxy …. is not expected and this is due to the fact that I’m returning from WCF a couple of classes that are mapped with NHIbernate, the entity returned has a property of type Customer that is a lazy property, thus at runtime it is represented by a dynamic proxy that is not known to WCF. The solution is trivial, just issue a Fetch(obj => obj.Client) in the LINQ query to fetch Client and avoiding NH to create a proxy, but the key point is that with WCF trace listener, finding problems in WCF is matter of few seconds.

Gian MAria.

Since I’m strongly convinced that in a full OOP approach to problem objects should not have nor setter nor getter, most of the work and complexities of an ORM is simply not needed, because you usually retrieve objects from the storage with only one function GetById and nothing else. In my long experience with NHibernate, I verified that most of the problem arise when you need to show data in UI in specific format and you start to write complex Query in HQL or ICRiteria or LINQ, then you need to spend time with NHProfiler to understand if the queries are good enough to run on production system and when objects changes a little bit you need to rewrite a lot of code to suite the new Object Model. This last point is the real pain point in DDD, where you usually should create Object Model that will be manipulated a lot before reaching a good point, after all the main value of DDD approach is being able to create a dialog with a DOMAIN EXPERT and it is impossible to find a good Object Models at the first tentative. If refactoring a model become painful, you are not allowed to modify it with easy, you are going away from DDD approach.

This is where CQRS can help you, for all objects belonging to the domain you need only to Save, LoadById, Update and delete, because every read model should be defined somewhere else. In such a scenario an ORM is really useful, because if you need to store objects inside Relational Database you can leave the ORM all the work to satisfy the CRUD part, where the R is the method GetById. To start easily with this approach you can create SQL View or stored procedures for all the Read Models you need; this imply that whenever the structure of the Domain Model changes, you need only to change all affected Read Models, some view and some stored procedure, but you have no need to refactor the code.

In this situation the ORM can really helps you, because if you change the Domain Model, you should only change the mapping, or let some Mapping by convention do this for you (ConfORM for NH is an example), regenerate the database and update only affected Read Models. If your domain is really anemic, if you expose properties from objects, even only with getters, whenever you change a domain class you should answer the question “If I change this property, what other domain objects will be affected? How many service class will be affected? How many query issued from Views will be affected?”. If you are not able to create a Read Model with SQL View or stored procedure, you can write a denormalizer that listens for DOMAIN EVENTS and populate the Read Model accordingly. In my opinion this is the scenario where an ORM can really helps you.

In such a situation a NoSql database can dramatically simplify your life, because you do not need an ORM anymore, cause you are able to save object graps into the storage directly, and you can create Read Models with Map/Reduce or with denormalizers.

But sadly enough, ORM are primarily used to avoid writing SQL and persist completely anemic domain, where all the logic reside on services. In such a scenario it is easy to abuse an ORM and probably in the long term the ORM could become much more a pain than a real help.

Gian Maria.

[Fact]
public void Verify_do_not_execute_task_if_interval_is_not_elapsed()
{
    using (ShimsContext.Create())
    {
        Int32 callCount = 0;
        PerformHeavyTask sut = new PerformHeavyTask(10, () => callCount++);
        DateTime startDate = new DateTime(2012, 1, 1, 12, 00, 00);
        ShimDateTime.NowGet = () =>  startDate;
        sut.Execute();
        ShimDateTime.NowGet = () => startDate.AddMinutes(9);
        sut.Execute();
        Assert.Equal(1, callCount);
    }
}

I can also change the point of view and write a test that uses a shim to isolate the SUT, this is a less common scenario but it can be also really interesting, because it shows you how you can write simple White box Unit Tests isolating part of the SUT. The term White Box is used because this kind of Unit Test are created with a full knowledge of the internal structure of the SUT, in my situation I have a private method called CanExecute() that return true/false based on the interval of time passed from the last execution and since it is private it makes difficult for me to test the SUT.

private Boolean CanExecute() {

    return DateTime.Now.Subtract(lastExecutionTime)
        .TotalMinutes >= intervalInMinutes;
}

But I can create a Shime on the SUT and isolate calls to the CanExecute(), making it return the value I need for the test, here is an example

[Fact]
public void Verify_can_execute_is_honored()
{
    using (ShimsContext.Create())
    {
        Int32 callCount = 0;
        PerformHeavyTask sut = new PerformHeavyTask(10, () => callCount++);
        ShimPerformHeavyTask shimSut = new ShimPerformHeavyTask(sut);
        shimSut.InstanceBehavior = ShimBehaviors.Fallthrough;
        shimSut.CanExecute = () => false;
        sut.Execute();
        Assert.Equal(0, callCount);
    }
}

To write this test I’ve added another fake assembly on the assembly that contains the PerformHeavyTask class to create shim for the SUT. This test basically create a ShimPerformHeavyTask (a shim of my SUT) passing an existing instance to the SUT to the constructor of the shim, then I set the InstanceBehavior to ShimBehaviors.Fallthrough to indicate to the Shim Library to call original SUT method if the method was not isolated. At this point I can simply isolate the call to the CanExecute() private and non-virtual method, specifying to the shim to return the value false, then I call the Execute() method and verify that the heavy task is not executed.

This test shows how to create a shim of the SUT to isolate calls to its private methods, thanks to the Fallthrough behavior; if you forget to change the InstanceBehavior the test will fail with an exception of type ShimNotImplementedException, because the default behavior for a Shim is to throw an exception for any method that is not intercepted. Thanks to shim library you can simply isolate every part of the SUT, making easier to write Unit Test for classes written with no TDD and no Unit Testing in mind.

Gian Maria.