c# - 在 WCF 中运行时切换服务协定实现

Question

我如何在运行时切换服务契约的实现？

假设我有:

[ServiceContract]
public interface IService {
    [OperationContract]
    DoWork();
}

public class ServiceA : IService {
    public string DoWork() {
        // ....
    }
}

public class ServiceB : IService {
    public string DoWork() {
        // ....
    }
}

我希望能够在配置文件或数据库中的值之间切换正在使用的实现。是否也可以在 WCF 服务热的时候执行此操作？

Answer 1

您需要通过实现 IServiceBehavior 来编写服务行为，并使用实例提供程序来初始化服务实例。下面初始化一个新的服务实例，你可以实现不同的逻辑:

public class XInstanceProviderServiceBehavior : Attribute, IServiceBehavior
{        

    public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
    {
        foreach (var item in serviceHostBase.ChannelDispatchers)
        {
            var dispatcher = item as ChannelDispatcher;
            if (dispatcher != null) 
            {
                dispatcher.Endpoints.ToList().ForEach(endpoint =>
                {
                    endpoint.DispatchRuntime.InstanceProvider = new XInstanceProvider(serviceDescription.ServiceType);
                });
            }
        }
    }

    public void Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
    {
    }

    public void AddBindingParameters(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints, BindingParameterCollection bindingParameters)
    {
    }
}

让您的实例提供者类实现 IInstanceProvider 并在 GetInstance 方法中返回相关实例。

public XInstanceProvider :IInstanceProvider
{
    ...

    public object GetInstance(InstanceContext instanceContext, System.ServiceModel.Channels.Message message)
    {
        return new ServiceX();
    }
}

那么你只需要在服务中添加servicebehaviour即可；像

[XInstanceProviderServiceBehavior()]    
    public class MyService : IMyService