如何使用响应式扩展在域​​服务中调用 Silverlight RIA InvokeOperation？

Question

有谁知道我将如何使用响应式扩展调用 RIA InvokeOperation？一旦调用全部完成，我需要处理来自 Silverlight 中多个异步调用的一些数据。在我的测试中，我将几个字符串与查询结果组合在一起，现在需要添加对 RIA 域服务调用方法的调用结果，结果卡住了。

我在 RIA 域服务端的简单测试函数（完成非 RX 样式）如下所示：

    [Invoke]
    public string DomainServiceFunction()
    {
        return "hello";
    }

在客户端，这段老式代码调用方法，是我想用 RX 实现的部分：

    private void CallDomainServiceFunction(object sender, RoutedEventArgs e)
    {
        DomainService1 DomainContext = new DomainService1();   
        InvokeOperation invokeOp = DomainContext.DomainServiceFunction(OnInvokeCompleted, null);
    }

    private void OnInvokeCompleted(InvokeOperation invOp)
    {
        Debug.WriteLine(invOp.Value);//This prints "hello".
    }

我编写了一些测试代码，它结合了来自多个来源的数据（我也想在其中添加 RIA InvokeOperation 调用）。它用几个字符串和一个查询返回的实体组成一个元组：

    private void PrintProperty1()
    {
        GISDomainContext DomainContext = new GISDomainContext();
        //Query the database to get information for a property using the folio number.
        var loadProperty = from loadOperation in DomainContextExtensions
              .LoadAsync(DomainContext, DomainContext.GetPropertyNoOwnersByFolioQuery("19401006.000"))
                            select loadOperation;
        //Zip up the property entity with a string for testing purposes.
        var Data = Observable.Return("a bit of text ")
            .Zip((Observable.Return("some more text")
            .Zip(loadProperty, (a, b) => Tuple.Create(a, b))), (a,b) => Tuple.Create(a,b));
        //Add a bit more stuff just to show it can be done.

        //THIS IS WHERE I WOULD ALSO ZIP WITH THE VALUE RETURNED FROM AN InvokeOperation.

        Data.Subscribe
        (
            //When all the required data are prepared then proceed...
            r => //On Next 
            {
                Debug.WriteLine("OnNext: " + r.Item1 + ", " + r.Item2.Item1 + ", " + r.Item2.Item2.Entities.First().folio.ToString());
                //results: "OnNext: a bit of text , some more text, 19401006.000"
                //At this point the data are all now available for further processing.
            },
            r => //On Error
            {
                Debug.WriteLine("Error in PrintProperty1: " + r.ToString());
            },
            () =>//On Completed
            {
                Debug.WriteLine("Completed PrintProperty1");
            }
        );
    }

我怀疑 FromAsyncPattern 是关键，但显然 Silverlight 隐藏了 FromAsyncPattern 期望作为参数的 Begin/End 调用

引用自here：

“Silverlight 的重要说明！

Silverlight 的网络服务 生成的客户端代码有点烦人——它隐藏起来 BeginXXXX/EndXXXX 调用，大概是为了进行 Intellisense 清洁器。但是，它们并没有消失，您可以将它们取回的方法是 通过将 MyCoolServiceClient 对象转换为其底层接口 （即 LanguageServiceClient 对象有一个生成的 它实现的ILanguageServiceClient接口)"

有什么建议吗？

Answer 1

实际上，Silverlight 并没有隐藏任何东西。 RIA 服务工具生成的DomainContext 派生代理上不存在这些方法。

但这里有一个扩展方法，它将Invoke 操作包装成IObservable：

public static class DomainContextExtensions
{
  // The method takes in an invoke operation proxy method delegate
  // and returns an observable sequence factory
  public static Func<T1, IObservable<TResult>> FromInvokeOperation<T1, TResult>
    (Func<T1, Action<InvokeOperation<TResult>>, object, InvokeOperation<TResult>> operationDelegate)
  {
    Contract.Requires<ArgumentNullException>(operationDelegate != null, "operationDelegate");
    Contract.Ensures(Contract.Result<Func<T1, IObservable<TResult>>>() != null);

    return x1 =>
      {
        // the subject is a storage for the result.
        var subject = new AsyncSubject<TResult>();

        try
        {
          var invokeOperation = operationDelegate(x1, operation =>
            {
              // handle operation results

              if (operation.IsCanceled)
              {
                return;
              }

              if (operation.HasError)
              {
                subject.OnError(operation.Error);
                operation.MarkErrorAsHandled();
                return;
              }

              Contract.Assume(operation.IsComplete);
              subject.OnNext(operation.Value);
              subject.OnCompleted();
            }, null);

          // create the operation cancellation object
          var invokeOperationCancellation = Disposable.Create(() =>
          {
            // need to check if the operation has completed before the subscription is disposed
            if (!invokeOperation.IsComplete && invokeOperation.CanCancel)
            invokeOperation.Cancel(); // this might abort the web call to save bandwidth
          });

          // construct a new observable that adds invoke operation cancellation upon dispose
          return Observable.Create<TResult>(obs => new CompositeDisposable(invokeOperationCancellation, subject.Subscribe(obs)));
        }
        catch (Exception ex)
        {
          return Observable.Create<TResult>(obs =>
            {
              obs.OnError(ex);
              return Disposable.Empty;
            });
        }
      };
  }
}

这应该可以，虽然我还没有测试过。

用法：

var context = ... // get your DomainContext
var param = ... // operation parameter
// This will create the observable:
var o = DomainContextExtensions.FromInvokeOperation</*Parameter type goes here*/, /*Result type goes here*/>(context.YourOperationMethod)(param);
o.Subscribe(...); // subscribe as you wish or build a query

您必须编写额外的方法来支持具有不同数量参数的调用操作。