如何构建批量返回数据的WCF服务答案

【问题标题】：How to build a WCF Service that returns data in batches如何构建批量返回数据的WCF服务
【发布时间】：2013-10-19 06:03:32
【问题描述】：

我正在尝试构建一个接收请求记录并为这些记录返回字符串响应的 WCF 服务。我正在接受一系列请求记录。在这个数组中，一些记录被快速处理（“快速记录”），而另一些则需要时间（“慢速记录”）。那么，是否可以先返回快记录，然后再发送慢记录，而不是等待所有记录被处理？客户端会立即更新屏幕中的快记录，并在出现时更新慢记录。

如何使用 WCF 服务做到这一点？

【问题讨论】：

两种方法：GetFastRecords & GetSlowRecords
如果客户端也在 .NET 中实现，则可能是双工服务。或者轮询，该方法立即返回“快速记录”，客户端每隔一段时间调用另一个方法，直到它拥有所有“慢速记录”。

标签： c# .net wcf

【解决方案1】：

如果你有双工支持，我会通过回调来实现。

[ServiceContract]
public interface IMyServiceCallback
{        
    [OperationContract(IsOneWay = true)]        
    void OnRecordResult(string result);
}

[ServiceContract(CallbackContract = typeof(IMyServiceCallback))]
public interface IMyService
{
    [OperationContract(IsOneWay = true)]
    void GetRecords(string parameter);
}

public class MyService: IMyService
{
    public void GetRecords(string parameter)
    {
        var callback = OperationContext.Current.GetCallbackChannel<IMyServiceCallback>();

        using(var resultCollection = ProcessRecords(parameter))
        {
            foreach(var record in resultCollection.GetConsumingEnumerable())
            {
                //Transmit the results back to the client as they get put in to resultCollection.
                callback.OnRecordResult(record);
            }
        }

        //We return null as a signal that we are done reporting results, you could also add a 2nd method to the callback to represent being done.
        callback.RecordResult(null);
    }

    private static BlockingCollection<string> ProcessRecords(string parameter)
    {
         var collection = new BlockingCollection<string>();

         //We populate the blocking collection in a background thread.
         Task.Run(() => StartProcessingRecords(parameter, collection);

         return collection;
    }

    private static void StartProcessingRecords(string parameter, BlockingCollection<string> collection)
    {
        //...
    }
}

这是你如何在客户端使用它

public class MyServiceClient : DuplexClientBase<IMyService>
{
    public MyServiceClient(object callbackInstance, Binding binding, EndpointAddress remoteAddress)
        : base(callbackInstance, binding, remoteAddress) { }
}

public class MyServiceCallbackClient : IMyServiceCallback
{
    public event EventHandler<string> RecordResult; //If you are not using .net 4.5 you will need a custom class.

    void IMyServiceCallback.OnRecordResult(string result)
    {
       var tmp = RecordResult;
       if(tmp != null)
           tmp(this, result);
    }
}

IEnumerable<string> GetRecords(string parameter)
{
    var uri = //...
    var binding = //...

    using(var collection = new BlockingCollection<string>())
    {
        var callback = new MyCallbackClient();
        callback.RecordResult += (o, result) =>
        {
             if(result != null)
                 collection.Add(result);
             else
                 collection.CompleteAdding(); //when we get a null we mark the collection complete
        }


        var client = new MyServiceClient(callback, binding, new EndpointAddress(uri));
        var proxy = client.ChannelFactory.CreateChannel();
        proxy.GetRecords();

        foreach(var record in collection.GetConsumingEnumerable())
        {
            yield return record;
        }

        client.Close();
     }
}

【讨论】：

【解决方案2】：

据我所知，您必须在 WCF 中实现 Websocket 才能完全满足您的要求。你可以在http://www.codeproject.com/Articles/341413/What-s-new-in-WCF-4-5-WebSocket-support-Part-2-of看到更多细节

【讨论】：