wcf – 基于事件和基于回调/委托的异步方法之间的区别？

2023年6月20日 294次阅读

使用svcutil.exe时,我注意到了这个开关,/ tcv：Version35.文档说这个：

Version35: Use /tcv:Version35 if you
are generating code for clients that
use .NET Framework 3.5. By using this
value, the SvcUtil.exe tool generates
code that references functionality in
.NET Framework 3.5 and previous
versions. When using /tcv:Version35
with the /async switch, both
event-based and
callback/delegate-based asynchronous
methods are generated. In addition,
support for LINQ-enabled DataSets and
DateTimeOffset is enabled.

基于事件和基于回调/委托的异步模型有什么区别？

编辑：是一种更新/更好的方式？当我不使用/ tcv：Version35开关时,我只获得BeginXXX和EndXXX方法. Silverlight使用XXXAsync,它告诉我应该使用基于事件的(XXXAsync)方法并使用此开关.

最佳答案 让我们像这样定义一个WCF服务：

namespace StackOverflow
{
    [ServiceContract]
    public interface ITest
    {
        [OperationContract]
        string GetName();
    }

    public class Test : ITest
    {
        public string GetName()
        {
            return "Joel Spolsky";
        }
    }
}

如果您对此运行svcutil,您将获得以下客户端定义：

public partial class TestClient : System.ServiceModel.ClientBase<ITest>, ITest
{
    // Other details elided...    

    public string GetData(int value)
    {
        return base.Channel.GetData(value);
    }
}

如果使用/ async标志再次运行svcutil,您将获得以下客户端定义：

public partial class TestClient : System.ServiceModel.ClientBase<ITest>, ITest
{
    // Other details elided...

    public event System.EventHandler<GetDataCompletedEventArgs> GetDataCompleted;

    public string GetData(int value)
    {
        return base.Channel.GetData(value);
    }

    [EditorBrowsableAttribute(EditorBrowsableState.Advanced)]
    public System.IAsyncResult BeginGetData(int value, System.AsyncCallback callback, object asyncState)
    {
        return base.Channel.BeginGetData(value, callback, asyncState);
    }

    [EditorBrowsableAttribute(EditorBrowsableState.Advanced)]
    public string EndGetData(System.IAsyncResult result)
    {
        return base.Channel.EndGetData(result);
    }

    public void GetDataAsync(int value, object userState)
    {
        if ((this.onBeginGetDataDelegate == null))
        {
            this.onBeginGetDataDelegate = new BeginOperationDelegate(this.OnBeginGetData);
        }
        if ((this.onEndGetDataDelegate == null))
        {
            this.onEndGetDataDelegate = new EndOperationDelegate(this.OnEndGetData);
        }
        if ((this.onGetDataCompletedDelegate == null))
        {
            this.onGetDataCompletedDelegate = new System.Threading.SendOrPostCallback(this.OnGetDataCompleted);
        }
        base.InvokeAsync(this.onBeginGetDataDelegate, new object[] {value}, this.onEndGetDataDelegate, this.onGetDataCompletedDelegate, userState);
    }
}

因此/ async标志只是为您提供了一种异步交互服务的方法,而不是默认的仅同步行为.

GetDataAsync()方法异步调用GetData()方法,并在通过GetDataCompleted事件完成时通知您.

BeginGetData()和EndGetData()方法使用委托的异步行为来异步调用GetData()方法.这类似于System.Windows.Forms.Control类上的BeginInvoke()和EndInvoke()方法或System.IO.Stream类上的BeginRead()和EndRead()方法.

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