使用Rx简化异步Silverlight Web服务请求

例如

public IObservable<XElement> GetReport(String reportName)
{
    return from client in Observable.Return(new WebserviceClient())
            from completed in Observable.CreateWithDisposable<GetReportDataCompletedEventArgs>(observer =>
                {
                    var subscription = Observable.FromEvent<GetReportDataCompletedEventArgs>(client,"GetReportDataCompleted")
                        .Take(1)
                        .SELEct(e => e.EventArgs)
                        .Subscribe(observer);
                    client.GetReportDataAsync(reportName);
                    return subscription;
                })
            from close in this.CloseClient(client)
            SELEct completed.Result;
}

为了使这更容易使用,我将CreateWithDisposable重构为一个可以与我的所有Web服务调用一起使用的公共函数,包括从事件args类型自动确定事件名称：

private IObservable<T> Callservice<T>(ICommunicationObject serviceClient,Action start) where T : AsyncCompletedEventArgs
{
    if (typeof(T) == typeof(AsyncCompletedEventArgs))
    {
        throw new InvalidoperationException("Event arguments type cAnnot be used to determine event name,use event name overload instead.");
    }

    String completedEventName = typeof(T).Name.TrimEnd("EventArgs");
    return Callservice<T>(serviceClient,start,completedEventName);
}

private IObservable<T> Callservice<T>(ICommunicationObject serviceClient,Action start,String completedEventName) where T : AsyncCompletedEventArgs
{
    return Observable.CreateWithDisposable<T>(observer =>
    {
        var subscription = Observable.FromEvent<T>(serviceClient,completedEventName).Take(1).SELEct(e => e.EventArgs).Subscribe(observer);
        start();
        return subscription;
    });
}

// Example usage:
public IObservable<XElement> GetReport(String reportName)
{
    return from client in Observable.Return(new WebserviceClient())
            from completed in this.Callservice<GetReportDataCompletedEventArgs>(client,() => client.GetReportDataAsync(reportName))
            from close in this.CloseClient(client)
            SELEct completed.Result;
}

/// <sumMary>
/// Asynchronously closes the web service client
/// </sumMary>
/// <param name="client">The web service client to be closed.</param>
/// <returns>Returns a cold observable sequence of a single success Unit.</returns>
private IObservable<AsyncCompletedEventArgs> CloseClient(WebserviceClient client)
{
    return this.Callservice<AsyncCompletedEventArgs>(client,client.CloseAsync,"CloseCompleted");
}

希望这有助于其他人！