CallbackBehaviorAttribute.ConcurrencyMode Property


Gets or sets whether a service supports one thread, multiple threads, or reentrant calls.

 property System::ServiceModel::ConcurrencyMode ConcurrencyMode { System::ServiceModel::ConcurrencyMode get(); void set(System::ServiceModel::ConcurrencyMode value); };
public System.ServiceModel.ConcurrencyMode ConcurrencyMode { get; set; }
member this.ConcurrencyMode : System.ServiceModel.ConcurrencyMode with get, set
Public Property ConcurrencyMode As ConcurrencyMode

Property Value

One of the ConcurrencyMode values; the default is Single.


The value is not one of the ConcurrencyMode values.


This property indicates whether an instance of a callback object supports one thread or multiple threads that execute concurrently, and if single-threaded, whether reentrancy is supported.

Setting ConcurrencyMode to Single instructs the system to restrict instances of the service to one thread of execution at a time, which frees you from dealing with threading issues. This is the default value. A value of Multiple means that service objects can be executed by multiple threads at any one time. In this case, you must ensure thread safety and state consistency.

Reentrant also restricts access to a single thread at a time. However, it enables calls out from an executing service method to return and reenter the executing service. A reentrant call can execute on a different managed thread, but in this case the original thread is blocked for the duration of the reentrant call.

Generally, if a message arrives for an instance that violates its concurrency mode, the message waits until the instance is available, or until it times out.

In addition, if the ConcurrencyMode is set to Single and a reentrant call is blocked while waiting for the instance to be freed, the system detects the deadlock and throws an exception.

For more information about concurrency, see ServiceBehaviorAttribute.ConcurrencyMode and Sessions, Instancing, and Concurrency.

Applies to