Silverlight同步(Synchronous)调用WCF服务

基于AutoResetEvent的同步实现

　　利用AutoResetEvent的线程等待特性，可以折中实现Silverlight同步调用远端WCF服务。其原理就是在Silverlight发起异步调用远端WCF的时候进行线程阻塞，比记录异步调用远端WCF服务接口的完成事件，当异步调用完成后就终止线程阻塞，从而获取状态事件对象中或得调用远程接口所返回的结果。由于视图模型对象实现了INotifyPropertyChanged接口能够及时的更新界面元素，以此间接的就实现了同步方式调用。

public class AsyncCallStatus<T>
{
    public AsyncCallStatus()
    {

    }

    public T CompletedEventArgs { get; set; }
}




public class BookFacade
{
    private AutoResetEvent autoResetEvent = new AutoResetEvent(false);

    public void GetBook(BookViewModel viewModel)
    {
        if (viewModel == null)
        {
            throw new ArgumentNullException("viewModel", "参数不能为空。");
        }

        DataService.DataServiceClient client = new DataService.DataServiceClient();
        client.GetBookCompleted += client_GetBookCompleted;

        var status = new AsyncCallStatus<GetBookCompletedEventArgs>();
        client.GetBookAsync(status);
        //阻塞线程
        autoResetEvent.WaitOne();

        if (status.CompletedEventArgs.Error != null)
        {
            throw status.CompletedEventArgs.Error;
        }
        var book = status.CompletedEventArgs.Result;
        viewModel.ID = book.ID;
        viewModel.Name = book.Name;
        viewModel.Author = book.Author;
        viewModel.Price = book.Price;
    }

    private void client_GetBookCompleted(object sender, GetBookCompletedEventArgs e)
    {
        var status = e.UserState as AsyncCallStatus<GetBookCompletedEventArgs>;

        status.CompletedEventArgs = e;
        //终止线程阻塞
        autoResetEvent.Set();
    }
}