ConcurrencyMode 枚举

定义

命名空间:

System.ServiceModel

程序集:

System.ServiceModel.Duplex.dll

程序集:

System.ServiceModel.dll

指定服务类是支持单线程还是多线程操作模式。

public enum class ConcurrencyMode

public enum ConcurrencyMode

type ConcurrencyMode = 

Public Enum ConcurrencyMode

继承

Object

ValueType

Enum

ConcurrencyMode

字段

Multiple	2	服务实例是多线程的。 无同步保证。 因为其他线程可以随时更改服务对象，所以必须始终处理同步与状态一致性。
Reentrant	1	服务实例是单线程的，且接受可重入调用。 可重入服务接受在调用其他服务的同时进行调用；因此在调出之前，您需要负责让对象的状态一致，而在调出之后，必须确认本地操作数据有效。 请注意，只有通过 WCF 通道调用其他服务，才能解锁服务实例。 在此情况下，已调用的服务可以通过回调重入第一个服务。 如果第一个服务不可重入，则该调用顺序会导致死锁。 有关详细信息，请参阅 ConcurrencyMode。
Single	0	服务实例是单线程的，且不接受可重入调用。 如果 InstanceContextMode 属性为 Single，且其他消息在实例处理调用的同时到达，则这些消息必须等待，直到服务可用或消息超时为止。

示例

下面的代码示例演示了使用 Single、Reentrant 和 Multiple 之间的差异。 此示例不会在没有实际实现的情况下进行编译，但确实演示了 WCF 做出的线程保证的类型以及操作代码的含义。

using System;
using System.ServiceModel;

[ServiceContract]
public interface IHttpFetcher
{
  [OperationContract]
  string GetWebPage(string address);
}

// These classes have the invariant that:
//     this.slow.GetWebPage(this.cachedAddress) == this.cachedWebPage.
// When you read cached values you can assume they are valid. When
// you write the cached values, you must guarantee that they are valid.
// With ConcurrencyMode.Single, WCF does not call again into the object
// so long as the method is running. After the operation returns the object
// can be called again, so you must make sure state is consistent before
// returning.
[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Single)]
class SingleCachingHttpFetcher : IHttpFetcher
{
    string cachedWebPage;
    string cachedAddress;
    readonly IHttpFetcher slow;

    public string GetWebPage(string address)
    {
        // <-- Can assume cache is valid.
        if (this.cachedAddress == address)
        {
            return this.cachedWebPage;
        }

        // <-- Cache is no longer valid because we are changing
        // one of the values.
        this.cachedAddress = address;
        string webPage = slow.GetWebPage(address);
        this.cachedWebPage = webPage;
        // <-- Cache is valid again here.

        return this.cachedWebPage;
        // <-- Must guarantee that the cache is valid because we are returning.
    }
}

// With ConcurrencyMode.Reentrant, WCF makes sure that only one
// thread runs in your code at a time. However, when you call out on a
// channel, the operation can get called again on another thread. Therefore
// you must confirm that state is consistent both before channel calls and
// before you return.
[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Reentrant)]
class ReentrantCachingHttpFetcher : IHttpFetcher
{
  string cachedWebPage;
  string cachedAddress;
  readonly SlowHttpFetcher slow;

  public ReentrantCachingHttpFetcher()
  {
    this.slow = new SlowHttpFetcher();
  }

  public string GetWebPage(string address)
  {
    // <-- Can assume that cache is valid.
    if (this.cachedAddress == address)
    {
        return this.cachedWebPage;
    }

    // <-- Must guarantee that the cache is valid, because
    // the operation can be called again before we return.
    string webPage = slow.GetWebPage(address);
    // <-- Can assume cache is valid.

    // <-- Cache is no longer valid because we are changing
    // one of the values.
    this.cachedAddress = address;
    this.cachedWebPage = webPage;
    // <-- Cache is valid again here.

    return this.cachedWebPage;
    // <-- Must guarantee that cache is valid because we are returning.
  }
}

// With ConcurrencyMode.Multiple, threads can call an operation at any time.
// It is your responsibility to guard your state with locks. If
// you always guarantee you leave state consistent when you leave
// the lock, you can assume it is valid when you enter the lock.
[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple)]
class MultipleCachingHttpFetcher : IHttpFetcher
{
  string cachedWebPage;
  string cachedAddress;
  readonly SlowHttpFetcher slow;
  readonly object ThisLock = new object();

  public MultipleCachingHttpFetcher()
  {
    this.slow = new SlowHttpFetcher();
  }

  public string GetWebPage(string address)
  {
    lock (this.ThisLock)
    {
      // <-- Can assume cache is valid.
      if (this.cachedAddress == address)
      {
          return this.cachedWebPage;
          // <-- Must guarantee that cache is valid because
          // the operation returns and releases the lock.
      }
      // <-- Must guarantee that cache is valid here because
      // the operation releases the lock.
    }

    string webPage = slow.GetWebPage(address);

    lock (this.ThisLock)
    {
      // <-- Can assume cache is valid.

      // <-- Cache is no longer valid because the operation
      // changes one of the values.
      this.cachedAddress = address;
      this.cachedWebPage = webPage;
      // <-- Cache is valid again here.

      // <-- Must guarantee that cache is valid because
      // the operation releases the lock.
    }

    return webPage;
  }
}

注解

ConcurrencyMode 与 ConcurrencyMode 属性一起使用，可指定服务类是支持单线程还是多线程操作模式。 单线程操作可以是可重入操作，也可以是不可重入操作。

下表显示了何时Windows Communication Foundation (WCF) 允许在另一个操作正在进行时调用，具体取决于该ConcurrencyMode操作。

ConcurrencyMode 值	是否允许调用新操作？
Single	从不。
折返	仅在调用其他服务或回调时。
多种	始终。