为什么我不能像添加服务引用那样使用任务生成代理？

Question

使用Visual Studio 2017 15.5.4 (.NET 4.7.02053)，我可以创建一个控制台应用程序，然后添加一个服务引用，生成一个带有同步签名和基于Task的异步签名的代理。

[System.CodeDom.Compiler.GeneratedCodeAttribute("System.ServiceModel", "4.0.0.0")]
[System.ServiceModel.ServiceContractAttribute(Namespace="urn:hpexstream-services/Engine", ConfigurationName="ServiceReference1.EngineWebService")]
public interface EngineWebService {

    // CODEGEN: Parameter 'return' requires additional schema information that cannot be captured using the parameter mode. The specific attribute is 'System.Xml.Serialization.XmlElementAttribute'.
    [System.ServiceModel.OperationContractAttribute(Action="urn:hpexstream-services/Engine:EngineWebService:ComposeRequest", ReplyAction="urn:hpexstream-services/Engine:EngineWebService:ComposeResponse")]
    [System.ServiceModel.FaultContractAttribute(typeof(ConsoleApp4.ServiceReference1.EngineServiceException), Action="urn:hpexstream-services/Engine:EngineWebService:Compose:Fault:EngineServiceExcept" +
        "ion", Name="EngineServiceException")]
    [System.ServiceModel.XmlSerializerFormatAttribute(SupportFaults=true)]
    [return: System.ServiceModel.MessageParameterAttribute(Name="return")]
    ConsoleApp4.ServiceReference1.ComposeResponse Compose(ConsoleApp4.ServiceReference1.ComposeRequest request);

    [System.ServiceModel.OperationContractAttribute(Action="urn:hpexstream-services/Engine:EngineWebService:ComposeRequest", ReplyAction="urn:hpexstream-services/Engine:EngineWebService:ComposeResponse")]
    System.Threading.Tasks.Task<ConsoleApp4.ServiceReference1.ComposeResponse> ComposeAsync(ConsoleApp4.ServiceReference1.ComposeRequest request);
}

然而当我使用 Developer Command Prompt v15.5.4 和 Svcutil.exe 生成相同的代理时，我只得到了基于经典 IAsyncResult 的 Begin 和 End 方法。这里是我尝试过的各种命令语句:

D:\xyz>svcutil http://example.com/EngineService/EngineService?wsdl /async

D:\xyz>svcutil http://example.com/EngineService/EngineService?wsdl /async /tcv:Version35

[System.CodeDom.Compiler.GeneratedCodeAttribute("System.ServiceModel", "4.0.0.0")]
[System.ServiceModel.ServiceContractAttribute(Namespace="urn:hpexstream-services/Engine", ConfigurationName="EngineWebService")]
public interface EngineWebService
{

    // CODEGEN: Parameter 'return' requires additional schema information that cannot be captured using the parameter mode. The specific attribute is 'System.Xml.Serialization.XmlElementAttribute'.
    [System.ServiceModel.OperationContractAttribute(Action="urn:hpexstream-services/Engine:EngineWebService:ComposeRequest", ReplyAction="urn:hpexstream-services/Engine:EngineWebService:ComposeResponse")]
    [System.ServiceModel.FaultContractAttribute(typeof(hpexstreamservices.Engine.EngineServiceException), Action="urn:hpexstream-services/Engine:EngineWebService:Compose:Fault:EngineServiceExcept" +
        "ion", Name="EngineServiceException")]
    [System.ServiceModel.XmlSerializerFormatAttribute()]
    [return: System.ServiceModel.MessageParameterAttribute(Name="return")]
    ComposeResponse Compose(ComposeRequest request);

    [System.ServiceModel.OperationContractAttribute(AsyncPattern=true, Action="urn:hpexstream-services/Engine:EngineWebService:ComposeRequest", ReplyAction="urn:hpexstream-services/Engine:EngineWebService:ComposeResponse")]
    System.IAsyncResult BeginCompose(ComposeRequest request, System.AsyncCallback callback, object asyncState);

    ComposeResponse EndCompose(System.IAsyncResult result);
}

如何强制Svcutil生成具有基于任务的签名的轻量级代理？

谢谢， Stephen

- Stephen Patten

---

尝试将/async放在URL之前... - ViRuSTriNiTy

你是通过尝试并确认它有效，还是在猜测？ - Stephen Patten

基本上是猜测，因为文档没有明确说明需要哪个顺序。 - ViRuSTriNiTy

Answer 1

通过阅读 Jon Skeet 的 评论 并推断出我所需的行为，我找到了答案。

你不需要传递 /a 参数，那就是强制使用 IAsyncResult 模式的参数。

- Stephen Patten