Visual Studio 2010 RTM Virtual Machine Now Available
The RTM version of Visual Studio 2010 and Team Foundation Server 2010 is now available for download as a virtual machine. The VM image also include a sample application and sample data to support the accompanying hands on labs. This image does not include the Visual Studio Lab Management 2010 but the team are working on it.
The virtual machine image comes in multiple flavours to support these virtualization technologies: Hyper-V, Windows Virtual PC (for Windows 7) and Virtual PC 2007 SP1. All of these images will expire on 15 Dec 2010.
Refer to Brian Keller’s post for additional details.
TFS 2010 Exam is Released
The 70-512 exam entitled “TS: Visual Studio Team Foundation Server 2010, Administration” exam was released late last week and can now be taken at Prometric test centres (registration link).
According to the Born to Learn blog post and the exam prep guide, the following four major areas are measured in this exam:
Since I have been working with our customers and partners on their development projects and ALM engagements and we use TFS most of the time, I decided to take the exam while it was hot so I did it earlier this week. I liked the exam contents and as always, enjoyed the experience of taking an MCP exam. There was only one question I found a bit ambiguous but I answered a customer query on the very same topic a couple of weeks ago so I knew the answer very well!
Providing a Reason for Stopping Project Collections in TFS 2010
When you stop a project collection in TFS 2010, it asks you to enter a reason why you are stopping that collection:
This text will be displayed to the users when they try to use an artifact in any of the projects in that project collection:
Note that this only affects those artifacts that are managed by TFS (work items, builds and source control items). Users can continue accessing the reports (handled by SSRS and SSAS) and documents (handled by SharePoint).
This is a minor feature but can be very useful when you need to service the project collection. It is still a good idea to make the users aware of the servicing plans in advance though!
Model-View-*
I find myself answering questions related to the presentation patterns repeatedly. Since I am a lazy person, I am writing this post to illustrate my understanding and interpretation of the Model-View-* patterns and their variations so I can refer back to this post later.
[Update] I have discussed these patterns and their contexts with my colleagues Josh and Rupert and have updated the post the reflect the result of our conversation. Thanks guys!
I understand the concerns the Model-View-* purists might have around the correctness and/or pureness of these diagrams so I do apologize for potential inaccuracies in advance and I welcome any suggestions / comments!
I am not going to explain every single Model-View-* pattern as you can find better explanations in other places. Instead, I will focus on the relationship between participant components in each pattern.
Let’s start with a list of patterns we are going to cover:
- MVC: Model-View-Controller
- MVP (Supervising Presenter): Model-View-Presenter with Supervising Presenter
- MVP (Passive View): Model-View-Presenter with Passive View
- MVVM: Model-View-ViewModel
- MVPoo: Model-View-ViewModel with some unwanted stuff (in the ViewModel)
This is a typical implementation of the good old MVC pattern. The Controller displays the View, make changes to its state and manage the navigation. The Controller can also update the Model (or ask the Model to update itself) and these updates are subsequently reflected in the View.
* What Happened to the MVP Pattern? *
As you may have noticed, the plain MVP (Model-View-Presenter) pattern is not in the above list. If you want to know why, read Martin Fowler’s note on retirement of the MVP pattern. Basically, he has split the MVP pattern into two: Supervising Presenter and Passive View. By looking at the next two diagrams, you will notice why they need to be separated.
In the Supervising Presenter variation of the MVP pattern, Controller becomes responsible for implementing the complex view logic where the data binding between the View and the Model is not able to support that complex logic. Data binding is still the primary mechanism for the communication between the View and the Model and the Controller is used only in those scenarios where data binding support falls short.
Passive View is the other variation of the MVP pattern and it brings the level of supervision of the Controller to the next level. The View no longer updates itself based on the Model and Controller becomes responsible for updating the View based on the data in the Model.
In the MVVM pattern, the View Model inherits most of the functionality that would otherwise be in the Controller. The user gestures are captured by the View and the View uses the commanding feature of the underlying framework to invoke the operations defined in the View Model. Note that there is a dotted line showing the data binding between the View and the Model. This highlights the ability for the view to be bound to the Model via the View Model. Although the View Model can have its own properties the View binds to, but it is very likely for the View Model to publish the underlying Models as properties so the View is effectively bound to the Model (via the View Model).
MVVM makes an assumption that the framework the application is built on provides strong support for two-way data binding between the View and the Model. This diagram shows how simple the MVVM pattern is but this pattern would be really hard (if not impossible) to implement before WPF because of the lack of strong support for commanding and data binding. Even with WPF, implementing a non-trivial application that follows the design shown above can be tricky and will usually require a lot of additional helpers and constructs if we want to rely on data binding only.
The MVPoo (or M-V-poo to be more precise as defined by its creator, Dr. WPF) pattern acknowledges the fact that there is a difference between the ideal world and the real world so that nice and clean implementation of the MVVM pattern is not always achievable. As a result, there will be scenarios where:
- View Model needs to update the View with mechanisms other than data binding.
- The user gesture captured by the View or the events raised by UI components needs to be handled by the View Model with mechanisms other than commanding
- …
So it is very likely that we will end up with a stinky version of the MVVM pattern. The MVPoo pattern acknowledges this fact and says this is okay but we need to try and make the components (with specific attention to the View Model!) less stinky as much as possible (by keeping the number of non-ideal elements/features in the View Model to a minimum).
Windows Server AppFabric is RTW
Windows Server AppFabric simplifies the process of creating, scaling and managing web and composite applications that run on IIS and includes the following components:
- AppFabric Caching Services (code-named “Velocity”)
- Caching services
- Cache client
- Cache administration
- AppFabric Hosting Services (code-named “Dublin”)
- Hosting services
- Hosting administration
You can get the RTW bits using the Web Platform Installer or downloading it directly from here.
The supported operating systems are both 32-bit and 64-bit editions of:
- Windows 7
- Windows Server 2008 R2
- Windows Vista SP2
- Windows Server 2008 SP2
You will also need a version of .NET Framework, depending on the features you want to use (more info):
- Hosting administration: .NET 4
- Hosting services: .NET 4
- Cache administration: .NET 4
- Caching service: .NET 4 and optionally .NET 3.5 (.NET 3.5 adds new capabilities)
- Cache client: .NET 4 and .NET 3.5 (depending on client application)
There are a number of additional resources linked from the landing page, including the Windows Server AppFabric wiki.
Deployment and Testing Automation
In Application Lifecycle Management (ALM) consulting engagements with customers, we usually cover the automation of various activities in the development process. Most of the development teams I work with have some sort of automated build system in place. The automated build usually goes as far as compiling the solution(s) and then running some unit tests to verify the build. Build automation adds a lot of value but the true value of the development process automation can only be realised when we take that final step and automate the deployment and testing process too. This is because the automated build (without deployment) cannot tell if all of the system components are going to work together to meet the requirements. It is also very hard (if not impossible) to run any integration tests in such environment because there is no deployment so the tests we can run will be limited to those that are related to individual units or those that rely on mocking frameworks.
When I ask development teams why they don’t take that final step, this is what I usually hear back:
- Our environment and deployment process is very complex so we can’t automate it.
- We have a shared database server we use for development and it is constantly changing so we don’t have a reliable baseline to test against.
- We don’t store our configuration files in the source control because it contains sensitive information.
- We have different environments we use for development and testing and every one of those has its own settings so which one should we keep in the source control?
- We need some data to be available in the database for testing and since the database is changing, the base data set is changing too.
- If we want to include the deployment and testing in the process, it is going to take n (n>5) hours.
- …
There are various solutions to any of these issues and to be honest, none of these are a good excuse for not automating the deployment and testing. Points similar to the ones listed above highlight fundamental problems somewhere else in the development process so even if we don’t want to automate the deployment and testing, we are still going to be affected by those inefficiencies and problems.
For example, if our argument is that the database schema is constantly being changed (by a different team and probably on a different release cycle), this means when we decide to have a release, we have no idea if the latest version of the code is in sync with the database schema and scripts at that point. We may be lucky and manage to release in few hours but next time we may end up spending a day or two sorting out inconsistencies. The typical solution to this is to make sure the database artifacts are always in sync with the source code and are stored together with the code in the source control. Historically, maintaining the database scripts (especially the DDL change scripts) in source control has been a huge problem but today, we have great support from development tools in the market for managing the database artifacts (and their changes). Many of the teams I talk to are simply unaware of the developments we have made in these areas.
The point about having a dependency on the base test data is interesting too. If we don’t have a reliable set of test data for the code we are working with, we will end up copying a database from a previous release and then start making changes to that database to bring it in line with the latest version of the database schema. And guess what? Every developer needs to go through this error-prone process. As the testing team and other developers start testing, they will discover new sets of data that allows them to test new scenarios but since all of the developers have spent a considerable time on creating their “precious” test data, they will hang on to what they have. I am sure this is one of those experiences we have all had and we can spend a lot of time on maintaining our test data instead of implementing features for our product. The easiest solution to this challenge is to maintain a set of base test data and store it together with the source code in the source control. Yes somebody needs to maintain this but we are in a better position as less people need to be worried with maintenance of that data and other developers will get the latest test data when they get latest from the source control. This base test data can also be used by the automated processes for testing purposes.
Implementing an automated deployment and testing process is not trivial but is certainly achievable and there are things you can do to make it simpler. If you ask me to come up with #1 guideline in this area, I will say put all of the artifacts required for deployment in the source control but even more importantly, make sure they are in the right location! Nobody questions why we need to put the source code under source control but people usually miss other artifacts such as database artifacts and build and deployment scripts. The interesting point is that many teams actually put these artifacts somewhere under source control but they put it in the wrong location, which makes them less effective and those artifacts will be unusable when we want to automate deployment and testing. So what is the right location for the artifacts?
The basic idea is that all of the artifacts required for deployment should follow our branching hierarchy.
For example, if we have three branches (DEV, MAIN and REL), each branch needs its own copy of the artifacts. Why? Because we want to be able to deploy and test any of those branches independently. As you can see this is a fairly obvious (and simple) solution but many teams don’t do this for various reasons and that makes the automated deployment and testing very hard (or impossible).
As I said earlier, even if we are not going to automate deployment and testing, we will still benefit from following this structure and making sure all of the artifacts under each branch are consistent and in sync with one another. Once this structure is in place, the next step is to make sure we have the capability of creating and managing the target environments as we will be deploying and testing over and over again. [I am writing the next few sentences with my “good corporate citizen” hat on…] This is where tools such as Visual Studio Lab Management can help. Many developers and testers I talk to still haven’t heard of this great product or don’t know what it does so if you fall in that category, you may want to have a look at the resources (product team blog, videos) to find out more about it. Please note that at the time of writing this post, Visual Studio Lab Management is still in pre-release status so make sure you read the pre-release license terms (rtf) before installing it.
You will be amazed when you see how easy it is to automate the process of managing the target environments (which usually consists of one or more virtual machines) as part of the build process in TFS 2010.
The above diagram shows the list of activities provided out of the box and you can use the workflow editor for the build to customise the end-to-end process.
Creating Objects Without Calling the Constructor
When you use the new operator to create an instance of a class, the class constructor is called before the reference to the newly created object is returned. This also applies to the reflection scenarios where you call Activator.CreateInstance, which finds the right constructor based on the number, order and type of the parameters provided.
This is the expected behavior in most cases as you don’t want to work with an object that might be in an invalid state. However, there are cases where you don’t need to run the constructor. A good example is when you are deserializing an object from a byte stream. During deserialization, you will be using the values embedded in the incoming byte stream to initialize the member variables so there is no point in initializing those members in the constructor as they will be overwritten.
The formatters that ship with the .NET Framework (such as BinaryFormatter and DataContractSerializer) follow this approach as you can expect. There is a utility class called FormatterServices, which provides some of the underlying services to the formatters, including but not limited to object creation.
namespace System.Runtime.Serialization { public sealed class FormatterServices { public static void CheckTypeSecurity(Type t, TypeFilterLevel securityLevel); public static object[] GetObjectData(object obj, MemberInfo[] members); public static object GetSafeUninitializedObject(Type type); public static MemberInfo[] GetSerializableMembers(Type type); public static MemberInfo[] GetSerializableMembers(Type type, StreamingContext context); public static ISerializationSurrogate GetSurrogateForCyclicalReference(ISerializationSurrogate innerSurrogate); public static Type GetTypeFromAssembly(Assembly assem, string name); public static object GetUninitializedObject(Type type); public static object PopulateObjectMembers(object obj, MemberInfo[] members, object[] data); } }
When you call GetUninitializedObject or GetSafeUninitializedObject, an instance of the class is created and returned without calling the constructor of the class. But note that the member variables are set to null and zero. FormatterServices is a public class so you can use its published functionality inside your application but you need to be very careful when using Get(Safe)UninitializedObject. As explained in the MSDN documentation, when you use these methods you should immediately populate all fields to make sure the object is not left in an invalid state.
There are some other interesting operations in FormatterServices. For example, GetSerializableMembers returns a list of members that will be serialized by the classic formatters.
One final point on this topic. If you are deserializing an object from a byte stream and want to run a piece of code to initialize the object before it is used (for example to calculate some of the fields that were not included in the serialized format), you will need to use the serialization attributes. See my earlier post on this subject for more information.
