.NET Development Foundation/Services
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| .NET Development Foundation | |
|---|---|
| Chapters | Introduction · System types · Services · Configuration · Serialization · Security · Interoperability · Globalization · Annexes |
Contents |
[edit] Services, threading, and application domains
Exam objective: Implementing service processes, threading, and application domains in a .NET Framework application
[edit] Topics
[edit] Services
The term service stands here for a Windows service. The basic definition of a Windows service is a long-running process that does not require a user interface. Why would you need a long-running process that does not require a user interface? Essentially two reasons:
- Doing maintenance tasks that do not need user intervention. A backup software for example will regularly check the backup schedule and execute the different backup tasks when needed. No user interface is needed for that.
- Responding to requests that come from other processes or from the operating system. An http server such as IIS (Windows component that process web requests) will receive http requests coming from client browsers and produce responses (html pages) to those same browsers. A database process is another good example. Again the http server does not need a user interface because the interface with the client is managed by the client browser component.
The exam objectives concerning services are very basic and touch the first problems that you will encounter when dealing with them:
- Since the service has no user interface then who start and stop it. The answer is that the operating system executes the services directly but you have to ‘’register’’ your service to let the system know where it is and what to do with it (this is the installation process)
- A process with a user interface essentially waits for events coming from the user. How does a service ‘’work’’ in the absence of a message pump (the technique to get user input in a typical online application).
- If the service does a user interface function it will “hang” waiting for a non-existent user. How can you avoid that?
The more important and complicated design issues are not covered by this exam and will be treated by the enterprise development exam.
[edit] Multithreading
[edit] Application Domain
[edit] Classes, Interfaces, and tools
[edit] Implement, install, and control a service
Exam objective: Implement, install, and control a service
(Refer System.ServiceProcess namespace)
Inherit from ServiceBase class - MSDN
- A service is a long-running executable. It does not provide a user interface, and does not require any user to be logged onto the computer. Services run as System, but it is possible to choose to have them run under a different user account. The ServiceBase class is a base class for a service. It must be derived from when creating a new service.
- Almost all services will override the OnStart and OnStop methods of ServiceBase.
ServiceController class and ServiceControllerPermission class
- ServiceController class - MSDN
- ServiceControllerPermission class - MSDN
ServiceInstaller and ServiceProcessInstaller class
- ServiceInstaller - MSDN
- ServiceProcessInstaller class - MSDN
ServiceChangeDescription structure and ServiceChangeReason enumeration
- SessionChangeDescription structure - MSDN
- SessionChangeReason enumeration - MSDN
[edit] Develop multithreaded applications
Exam objective: Develop multithreaded .NET Framework applications
(Refer System.Threading namespace)
Thread class - MSDN
ThreadPool class - MSDN
ThreadStart delegate, ParameterizedThreadStart delegate, and SynchronizationContext class
- ThreadStart delegate - MSDN
-
- The simplest way to create a thread is to instantiate the Thread class. The Thread constructor takes a delegate argument. The ThreadStart delegate points to a method containing your logic. For example:
Thread t1 = new Thread (new ThreadStart(LengthyLogic));
public void LengthyLogic ()
{
// Logic code
}
- ParameterizedThreadStart delegate - MSDN
-
- When you start a thread, sometimes you need to pass in some data for processing. .NET 2.0 provides a new delegate, ParameterizedThreadStart, which takes a parameter of type object. The class has a new overload function Thread.Start. It allows you to specify the value to be passed into the thread. This approach is simple, but is not type-safe. Example:
Thread t1 = new Thread(new ParameterizedThreadStart(LengthyLogic));
// Use the overload of the Start method that has a parameter of type Object.
t1.Start(myData);
static void LengthyLogic(object data)
{
// Logic code
}
- SynchronizationContext class - MSDN
-
- The Code Project Example for SynchronizationContext Class [1]
Timeout class, Timer class, TimerCallback delegate, WaitCallback delegate, WaitHandle class, and WaitOrTimerCallback delegate
- Timeout class - MSDN
- Timer class - MSDN
- TimerCallback delegate - MSDN
- WaitCallback delegate - MSDN
- WaitHandle class - MSDN
- WaitOrTimerCallback delegate - MSDN
ThreadExceptionEventArgs class and ThreadExceptionEventHanlder class
- ThreadExceptionEventArgs class - MSDN
- ThreadExceptionEventHandler class - MSDN
ThreadState enumeration and ThreadPriority enumeration
- ThreadState enumeration - MSDN
- ThreadPriority enumeration - MSDN
ReaderWriterLock class - MSDN
AutoResetEvent class and ManualResetEvent class
- AutoResetEvent class - MSDN
- ManualResetEvent class - MSDN
IAsyncResult interface and ICancelableAsyncResult interface
- (Refer System namespace)
- IAsyncResult interface - MSDN
- ICancelableAsyncResult interface - MSDN
EventWaitHandle class, RegisterWaitHandle class, SendOrPostCallback delegate, and IOCompletionCallback delegate
- EventWaitHandle class - MSDN
- RegisterWaitHandle class - MSDN
-
- This is a typo in the exam list of objectives and the training kit. The term RegisterWaitForSingleObject should be saerch instead (see KB)
- SendOrPostCallback delegate - MSDN
- IOCompletionCallback delegate - MSDN
Interlocked class, NativeOverlapped structure, and Overlapped class
- Interlocked class - MSDN
- NativeOverlapped structure - MSDN
- Overlapped class - MSDN
ExecutionContext class, HostExecutionContext class, HostExecutionContext manager, and ContextCallback delegate
- ExecutionContext class - MSDN
- HostExecutionContext class - MSDN
- HostExecutionContext manager - MSDN
-
- In fact was is refered to here is the HostExecutionContextManager class
- ContextCallback delegate - MSDN
LockCookie structure, Monitor class, Mutex class, and Semaphore class MSDN]
- LockCookie structure - MSDN
- Monitor class - MSDN
- Mutex class - MSDN
- Semaphore class - MSDN
[edit] Using applications domains
Exam objective: Create a unit of isolation for common language runtime in a .NET Framework application by using application domains
(Refer System namespace)
Create an application domain - MSDN
- An application domain is a division of a process into multiple parts. Applications running in different application domains are as isolated as they would be in different processes.
- Application domains are easier to maintain and are faster because it is easier to communicate between application domains than between processes. An application domain can hold multiple assemblies.
Unload an application domain - MSDN
Configure an application domain - MSDN
Retrieve setup information from an application domain - MSDN
Load assemblies into an application domain - MSDN
