C#：WCF：接口继承和转换问题

我正在为WCF服务编写客户端，该服务支持同步和异步调用，而无需在通道中为合同中的每个方法实现5-6个不同的方法

我有一个基本接口（IServiceClient）和一个基于此接口类型的泛型类（ServiceClient），如下所示：

public interface IServiceClient { /* nothing here -- just for casting purpose */ }

public abstract class ServiceClient<TChannel> : ClientBase<TChannel> where TChannel : class, IServiceClient
{
    ....

    public T SyncCall<T>(string method, object[] args)
    {
        ....
        return (T)...
    }

    public ServiceCall<T> AsyncCall<T>(string method, object[] args)
    {
        return new ServiceCall<T>(this, method, args);
    }

    ....

    public class ServiceCall<T>
    {
        public ServiceCall(RemoteServiceClient<TChannel> service, string method, object[] args)
        {
            ...
        }

        ...

        public PageAsyncTask CreatePageAsyncTask(Action<T> onSuccess, Action<Exception> onFailure)
        {
            return new System.Web.UI.PageAsyncTask(...);
        }
    }
}

[ServiceContract]
public interface IMyServiceClient : IServiceClient
{
    ....

    [OperationContract]
    string GetWhatever(int index);
    [OperationContract]
    IAsyncResult BeginGetWhatever(int index, System.AsyncCallback callback, object asyncState);
    string EndGetWhatever(System.IAsyncResult result);

    ....
}


public partial class MyServiceClient : ServiceClient<IMyServiceClient>
{
    ....

    public string GetWhatever(int index)
    {
        return SyncCall<string>("GetWhatever", new object[] { index });
    }
    public ServiceCall<string> GetWhateverAsync(int index)
    {
        return AsyncCall<string>("GetWhatever", new object[] { index });
    }

    ....
}

public class MyWebControl : WebControl
{
    private void HandleFailure(System.Exception e) { .... }
    public void CallService<T>(ServiceClient<IServiceClient>.ServiceCall<T> func, System.Action<T> onSuccess, System.Action<Exception> onFailure)
    {
        this.Page.RegisterAsyncTask(func.CreatePageAsyncTask(onSuccess, onFailure ?? (e => this.HandleFailure(e))));
    }

    protected override void OnPreRender(EventArgs e)
    {
        base.OnPreRender(e);

        ....

        var client = new MyServiceClient(/*whatever*/);
        client.Open();
        CallService(client.GetWhateverAsync(index), this.OnResult, this.OnError);

        ....
    }

    public void OnResult(string result) { .... }
    public void OnError(Exception e) { .... }
}

公共接口IServiceClient{/*此处无任何内容--仅用于强制转换目的*/}
公共抽象类ServiceClient:ClientBase，其中TChannel:class，IServiceClient
{
....
公共T SyncCall（字符串方法，对象[]args）
{
....
返回（T）。。。
}
公共服务调用异步调用（字符串方法，对象[]args）
{
返回新的ServiceCall（此、方法、参数）；
}
....
公共类服务呼叫
{
公共服务调用（RemoteServiceClient服务，字符串方法，对象[]args）
{
...
}
...
public PageAsyncTask CreatePageAsyncTask（操作成功，操作失败）
{
返回新的System.Web.UI.PageAsyncTask（…）；
}
}
}

另外，还有另一个接口（实际契约）扩展基本接口，并基于派生接口实现ServiceClient类，如下所示：

public interface IServiceClient { /* nothing here -- just for casting purpose */ }

public abstract class ServiceClient<TChannel> : ClientBase<TChannel> where TChannel : class, IServiceClient
{
    ....

    public T SyncCall<T>(string method, object[] args)
    {
        ....
        return (T)...
    }

    public ServiceCall<T> AsyncCall<T>(string method, object[] args)
    {
        return new ServiceCall<T>(this, method, args);
    }

    ....

    public class ServiceCall<T>
    {
        public ServiceCall(RemoteServiceClient<TChannel> service, string method, object[] args)
        {
            ...
        }

        ...

        public PageAsyncTask CreatePageAsyncTask(Action<T> onSuccess, Action<Exception> onFailure)
        {
            return new System.Web.UI.PageAsyncTask(...);
        }
    }
}

[ServiceContract]
public interface IMyServiceClient : IServiceClient
{
    ....

    [OperationContract]
    string GetWhatever(int index);
    [OperationContract]
    IAsyncResult BeginGetWhatever(int index, System.AsyncCallback callback, object asyncState);
    string EndGetWhatever(System.IAsyncResult result);

    ....
}


public partial class MyServiceClient : ServiceClient<IMyServiceClient>
{
    ....

    public string GetWhatever(int index)
    {
        return SyncCall<string>("GetWhatever", new object[] { index });
    }
    public ServiceCall<string> GetWhateverAsync(int index)
    {
        return AsyncCall<string>("GetWhatever", new object[] { index });
    }

    ....
}

public class MyWebControl : WebControl
{
    private void HandleFailure(System.Exception e) { .... }
    public void CallService<T>(ServiceClient<IServiceClient>.ServiceCall<T> func, System.Action<T> onSuccess, System.Action<Exception> onFailure)
    {
        this.Page.RegisterAsyncTask(func.CreatePageAsyncTask(onSuccess, onFailure ?? (e => this.HandleFailure(e))));
    }

    protected override void OnPreRender(EventArgs e)
    {
        base.OnPreRender(e);

        ....

        var client = new MyServiceClient(/*whatever*/);
        client.Open();
        CallService(client.GetWhateverAsync(index), this.OnResult, this.OnError);

        ....
    }

    public void OnResult(string result) { .... }
    public void OnError(Exception e) { .... }
}

[服务合同]
公共接口IMyServiceClient:IServiceClient
{
....
[经营合同]
字符串getwhere（int索引）；
[经营合同]
IAsyncResult BeginGetWhatever（int索引、System.AsyncCallback回调、object asyncState）；
字符串ENDGETWHERTH（System.IAsyncResult结果）；
....
}
公共部分类MyServiceClient:ServiceClient
{
....
公共字符串getwhere（int索引）
{
返回SyncCall（“getwhere”，新对象[]{index}）；
}
公共服务调用GetWhateverAsync（int索引）
{
返回AsyncCall（“getWhather”，新对象[]{index}）；
}
....
}

我尝试在控件中异步调用getWhather（int）方法，如下所示：

public interface IServiceClient { /* nothing here -- just for casting purpose */ }

public abstract class ServiceClient<TChannel> : ClientBase<TChannel> where TChannel : class, IServiceClient
{
    ....

    public T SyncCall<T>(string method, object[] args)
    {
        ....
        return (T)...
    }

    public ServiceCall<T> AsyncCall<T>(string method, object[] args)
    {
        return new ServiceCall<T>(this, method, args);
    }

    ....

    public class ServiceCall<T>
    {
        public ServiceCall(RemoteServiceClient<TChannel> service, string method, object[] args)
        {
            ...
        }

        ...

        public PageAsyncTask CreatePageAsyncTask(Action<T> onSuccess, Action<Exception> onFailure)
        {
            return new System.Web.UI.PageAsyncTask(...);
        }
    }
}

[ServiceContract]
public interface IMyServiceClient : IServiceClient
{
    ....

    [OperationContract]
    string GetWhatever(int index);
    [OperationContract]
    IAsyncResult BeginGetWhatever(int index, System.AsyncCallback callback, object asyncState);
    string EndGetWhatever(System.IAsyncResult result);

    ....
}


public partial class MyServiceClient : ServiceClient<IMyServiceClient>
{
    ....

    public string GetWhatever(int index)
    {
        return SyncCall<string>("GetWhatever", new object[] { index });
    }
    public ServiceCall<string> GetWhateverAsync(int index)
    {
        return AsyncCall<string>("GetWhatever", new object[] { index });
    }

    ....
}

public class MyWebControl : WebControl
{
    private void HandleFailure(System.Exception e) { .... }
    public void CallService<T>(ServiceClient<IServiceClient>.ServiceCall<T> func, System.Action<T> onSuccess, System.Action<Exception> onFailure)
    {
        this.Page.RegisterAsyncTask(func.CreatePageAsyncTask(onSuccess, onFailure ?? (e => this.HandleFailure(e))));
    }

    protected override void OnPreRender(EventArgs e)
    {
        base.OnPreRender(e);

        ....

        var client = new MyServiceClient(/*whatever*/);
        client.Open();
        CallService(client.GetWhateverAsync(index), this.OnResult, this.OnError);

        ....
    }

    public void OnResult(string result) { .... }
    public void OnError(Exception e) { .... }
}

公共类MyWebControl:WebControl
{
私有无效句柄失败（System.Exception e）{….}
public void CallService（ServiceClient.ServiceCall func，System.Action onSuccess，System.Action onFailure）
{
this.Page.RegisterAsyncTask（funct.CreatePageAsyncTask（onSuccess，onFailure？？（e=>this.HandleFailure（e））；
}
受保护的覆盖无效OnPreRender（EventArgs e）
{
基于预渲染（e）；
....
var client=newmyserviceclient（/*whatever*/）；
client.Open（）；
CallService（client.GetWhateverAsync（index）、this.OnResult、this.OnError）；
....
}
公共void OnResult（字符串结果）{….}
公共无效OnError（例外情况e）{….}
}

我发现两个编译错误：

Error 1 The best overloaded method match for 'MyWebControl.CallService<string>>(IServiceClient>.ServiceCall<string>, System.Action<string>, System.Action<System.Exception>)' has some invalid arguments
Error 2 Argument 1: cannot convert from 'ServiceClient<IMyServiceClient>.ServiceCall<string>' to 'ServiceClient<IServiceClient>.ServiceCall<string>'

错误1“MyWebControl.CallService>（IServiceClient>.ServiceCall，System.Action，System.Action）”的最佳重载方法匹配具有一些无效参数
错误2参数1:无法从“ServiceClient.ServiceCall”转换为“ServiceClient.ServiceCall”

显然，编译器似乎无法理解IMyServiceClient扩展了IServiceClient。我知道接口继承不像类继承那样工作；但我不知道如何解决这个编译器错误。我已经尝试在MyServiceClient类中添加一个新的ServiceCall实现，以在base中扩展它——但是编译器错误没有改变

顺便说一句，如果我将我的ServiceClient实现更改为基于IMyServiceClient，它就会工作。另外，只调用client.getwhater（index）（调用SyncCall方法）编译并运行良好

---

任何关于正在发生什么或编译器正在寻找什么的想法都会有所帮助。谢谢。

通过更改我控制中的CallService方法解决了此问题：

public void CallService<TChannel, T>(ServiceClient<TChannel>.ServiceCall<T> func, System.Action<T> onSuccess, System.Action<Exception> onFailure) where TChannel: class, IServiceClient
{ 
    this.Page.RegisterAsyncTask(func.CreatePageAsyncTask(onSuccess, onFailure ?? (e => this.HandleFailure(e)))); 
} 

public void CallService（ServiceClient.ServiceCall func，System.Action onSuccess，System.Action onFailure），其中TChannel:class，IServiceClient
{ 
this.Page.RegisterAsyncTask（funct.CreatePageAsyncTask（onSuccess，onFailure？？（e=>this.HandleFailure（e））；
} 

---

Thx.

这个问题与接口继承无关。事实上，泛型通常是不协变的：

ServiceClient

不能强制转换为

ServiceClient

，即使

IMyServiceClient

继承自

IServiceClient

不用担心；我自己解决了！太好了-那就接受你自己的答案吧，这样人们就不会一直看着它试图回答了！：）