WCF Interview Questions – Part 4
This WCF service tutorial is part-4 in series of WCF Interview Questions. Before reading this please go through the following articles in this series.
这是WCF问答教程的第四部分，在阅读之前请先去看下面列出来的文章。
WCF Interview Questions List – Part 4
- What is SOA (Service Oriented Architecture) and how WCF supports it?【什么是SOA（面向服务的架构），WCF是怎样支持它的。】
- What is ESB in SOA environment?【SOA环境中，什么是ESB】
- What is Transaction Propagation? And how WCF support it?【什么是事务传播，WCF是怎么支持它的？】
- Does all WCF bindings support for Transaction Propagation?【是不是所有的WCF绑定都支持事务传播？】
- What are the various Transaction Flow Options available in WCF?【WCF中可用的各种事务流选项是什么?】
- What is two-phase committed protocol?【什么是Two-Phase提交协议？】
- What is the role of transaction manager in WCF?【WCF中，事务管理器的作用是什么?】
- What are the supported transaction types in WCF?【WCF支持哪些事务类型？】
- How to enable the Performance Counters in WCF?【如何启用WCF的性能计数器?】
What is SOA (Service Oriented Architecture) and how WCF supports it?【什么是SOA（面向服务的架构），WCF是怎样支持它的。】
SOA is basically an architectural model that dictates few principles for building business applications in the form of independent, loosely coupled and interoperable services. These services are well defined, self-contained and can work together to achieve certain business functionality without depending on context or state of other services.
SOA是一种架构模型，它规定了一些原则，来创建形式独立的，松耦合的，可互操作的业务应用程序。这些定义非常好的，独立的服务，可以相互工作，达到某种业务功能，而不需要依赖上下文，或者其他服务的状态。
WCF supports almost all those principles dictated by Service Oriented Architecture for developing services; those are independent, loosely coupled and interoperable also. Please visit for detailed discussion on WCF and SOA.
WCF几乎支持所有面向服务架构的原则，用来开发服务。他们是独立的，松耦合的，同样也是可互操作的，想要了解更多详细的讨论，请看WCF and SOA.
What is ESB in SOA environment?【SOA环境中，什么是ESB】
In Service Oriented Architecture environment, ESB (Enterprise Service Bus) acts as a single interface for all messaging between applications and services in a loosely coupled manner. ESB is capable to call and subscribe different service provider’s methods and subscriptions respectively.
在面向服务的架构的环境中，ESB（企业服务总线）作为一个接口，为所有在应用程序和服务之间的消息传递，以一种松耦合的方式传递。ESB可以调用和区别不同的服务提供商的方法。
What is Transaction Propagation? And how WCF support it?【什么是事务传播，WCF是怎么支持它的？】
Transaction propagation is the ability to propagate transaction across the boundaries of a single service. Or in other words, we can say that a service can participate in a transaction that is initiated by a client.
In a SOA environment, transaction propagation becomes a key requirement. As we know that WCF supports SOA, so it provides support for transaction propagation as well.
事务传播就是在单个服务的界限间传播事务的能力。或者换句话说，一个服务可以加入到一个由客户端发起的事务中。在SOA的环境中，事务传播成为了一个关键的必须点。我们知道，WCF支持SOA，所以WCF同样支持事务传播。
To enable transaction propagation, we need to set the value of TransactionFlow property of the binding being used. This can be done programmatically as follows:
为了启动事务传播，我们需要设置所绑定的TransactionFlow 属性值，下面是具体的做法：
bindingBeingUsed.TransactionFlow = “true”;
Or It can be done declaratively by updating configuration file as follows:
或者可以通过修改配置文件，来启用事务传播，例如下面：
<wsHttpBinding>
<binding name=”binding1”
transactionFlow=”true” />
</wsHttpBinding>
</bindings>
Default value for TransactionFlow property is “False”.【默认的TransactionFlow 属性值是false】
Does all WCF bindings support for Transaction Propagation? 【是不是所有的WCF绑定都支持事务传播？】
No. Not all WCF bindings support transaction propagation. Only following list of bindings support for it.
不是的，并不是所有的WCF绑定都支持事务传播，仅仅只有下面列出来的绑定支持事务传播。
- wsHttpBinding
- netTcpBinding
- netNamedPipeBinding
- wsDualHttpBinding
- wsFederationHttpBinding
What are the various Transaction Flow Options available in WCF?【WCF中可用的各种事务流选项是什么?】
If a service is configured for Transaction Propagation, WCF further supports various options for service methods to be part of any transaction initiated outside service boundaries.
如果为服务配置事务传播，在服务边界之外，WCF将进一步支持服务的各种方法。
- NotAllowed Transaction Propagation is not allowed for particular service method. Its default value.
- Allowed Transaction Propagation is allowed but not compulsory.
- Mandatory Transaction Propagation is compulsory for that service method.
For example, Transaction Propagation is mandatory for CreditAccount service method in following code snippet.
例如下面的代码片段中，为CreditAccount服务方法设置事务的选项为强制的。
interface IPaymentService
{
[OperationContract]
[TransactionFlow(TransactionFlowOption.Mandatory)]
void CreditAccount(….);
}
What is two-phase committed protocol?【什么是Two-Phase提交协议？】
In a distributed transaction scenario, two-phase committed protocol is an algorithm that ensures all the participating processes in a distributed transaction are ready to be committed or roll backed.
在分布式的场景中，two-phase committed protocol是一种算法，它确保所有的流程参与到分布式的提交或者回滚中。
This is done in two phases:
- Prepare Phase
- Commit phase
What is the role of transaction manager in WCF? 【WCF中，事务管理器的作用是什么?】
Transaction manager while sitting on client side, initiate the transaction and coordinates with all the processes that participate in a distributed transaction to commit or roll back.
事务管理是在客户端设置的，它负责启动事务，并且协调所有参与到分布式中的进程，是提交或者是回滚。
What are the supported transaction types in WCF?【WCF支持哪些事务类型？】
Supported transaction types in WCF are:【WCF支持的事务类型有：】
- Light Weight【轻量级的】
- OLE Transactions【OLE事务】
- WS-Atomic Transactions【WS-Atomic事务】
How to enable the Performance Counters in WCF?【如何启用WCF的性能计数器?】
Simple way to enable Performance Counters supported by WCF is as follows:
简单的方式来启动WCF性能计数器，如下：
<diagnostics performanceCounters = “All” />
</system.serviceModel>
Above configuration setting will enable all categories of counters including ServiceModelService, ServiceModelEndpoint and ServiceModelOperation. Default value for it is “Off”.
上面的设置，将会启动所有种类的计数器，包括：ServiceModelService，ServiceModelEndpoint 和ServiceModelOperation，默认它的值是OFF。