(转载)Silverlight同步(Synchronous)调用WCF服务
时间：2011-05-20 来源：槑槑
原文链接:http://www.cnblogs.com/beniao/archive/2011/01/07/1929639.html
Silverlight的RIA应用中访问远端的WebService或WCF服务，都是通过异步线程模式调用的。在某些情况下我们的调用是需要同步进行，虽然Silverlight没有内置同步线程模式调用远端服务接口，但是我们可以通过多线程的处理来伪装出同步调用的实现。在.NET Framework的多线程编程中提供了丰富的线程接口，其中AutoResetEvent和ManualResetEvent在多线程编码中最为常用，本文将介绍如何通过AutoResetEvent的线程等待特性实现Silverlight同步调用远端WCF服务。
一、定义WCF服务
为了演示同步调用WCF服务的实现，提供一个简单的WCF服务接口，完成返回一本图书基本信息，WCF服务接口定义如下：
[ServiceContract]
public interface IDataService
{
[OperationContract]
Book GetBook();
}
public class Book
{
public int ID { get; set; }
public string Name { get; set; }
public string Author { get; set; }
public double Price { get; set; }
}
public interface IDataService
{
[OperationContract]
Book GetBook();
}
public class Book
{
public int ID { get; set; }
public string Name { get; set; }
public string Author { get; set; }
public double Price { get; set; }
}
接口提供一个返回图书基本信息的方法，包括图书编好，图书名，图书作者以及图书价格。接口具体的实现如下代码：
public class DataService : IDataService
{
public Book GetBook()
{
return new Book
{
ID = 1001,
Name = "《三国演义》",
Author = "罗贯中",
Price = 89.50
};
}
}
{
public Book GetBook()
{
return new Book
{
ID = 1001,
Name = "《三国演义》",
Author = "罗贯中",
Price = 89.50
};
}
}
如上提供可正常运行的WCF服务接口，在需要调用接口的地方通过WEB引用既可生成该服务的客户端代理对象。
二、基于MVVM模式的视图模型
MVVM模式的核心为INotifyPropertyChanged接口，对于实体模型对象和UI控件元素间提供了完善的同步更新特性。为了方便界面元素同步更新，这里引入了MVVP模式的简单应用。
public class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChangedEvent(string propertyName)
{
var handler = PropertyChanged;
if (handler != null)
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
{
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChangedEvent(string propertyName)
{
var handler = PropertyChanged;
if (handler != null)
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
还需要对应于服务接口中的Book对象定义一个ViewModel对象，详细如下代码所示：
public class BookViewModel : ViewModelBase
{
private int iD;
/// <summary>
/// 图书ID
/// </summary>
public int ID
{
get { return iD; }
set
{
iD = value;
RaisePropertyChangedEvent("ID");
}
}
private string name;
/// <summary>
/// 图书名称
/// </summary>
public string Name
{
get { return name; }
set
{
name = value;
RaisePropertyChangedEvent("Name");
}
}
private string author;
/// <summary>
/// 图书作者
/// </summary>
public string Author
{
get { return author; }
set
{
author = value;
RaisePropertyChangedEvent("Author");
}
}
private double price;
/// <summary>
/// 图书价格
/// </summary>
public double Price
{
get { return price; }
set
{
price = value;
RaisePropertyChangedEvent("Price");
}
}
}
{
private int iD;
/// <summary>
/// 图书ID
/// </summary>
public int ID
{
get { return iD; }
set
{
iD = value;
RaisePropertyChangedEvent("ID");
}
}
private string name;
/// <summary>
/// 图书名称
/// </summary>
public string Name
{
get { return name; }
set
{
name = value;
RaisePropertyChangedEvent("Name");
}
}
private string author;
/// <summary>
/// 图书作者
/// </summary>
public string Author
{
get { return author; }
set
{
author = value;
RaisePropertyChangedEvent("Author");
}
}
private double price;
/// <summary>
/// 图书价格
/// </summary>
public double Price
{
get { return price; }
set
{
price = value;
RaisePropertyChangedEvent("Price");
}
}
}
三、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 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();
}
}
{
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();
}
}
四、Silverlight前端调用
Siverlight前端就简单布局一个表单作为数据呈现界面，其代码如下：
<Grid x:Name="LayoutRoot" Background="White">
<Grid HorizontalAlignment="Left" Name="grid1" VerticalAlignment="Top" Width="300" Margin="20">
<Grid.RowDefinitions>
<RowDefinition Height="30"></RowDefinition>
<RowDefinition Height="30"></RowDefinition>
<RowDefinition Height="30"></RowDefinition>
<RowDefinition Height="30"></RowDefinition>
<RowDefinition Height="30"></RowDefinition>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="60"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<sdk:Label HorizontalAlignment="Left" Content="图书编号：" VerticalAlignment="Center" Grid.Column="0" Grid.Row="0"/>
<TextBox Text="{Binding ID}" Grid.Column="1" Grid.Row="0"></TextBox>
<sdk:Label HorizontalAlignment="Left" Content="图书名称：" VerticalAlignment="Center" Grid.Column="0" Grid.Row="1"/>
<TextBox Text="{Binding Name}" Grid.Column="1" Grid.Row="1"></TextBox>
<sdk:Label HorizontalAlignment="Left" Content="图书作者：" VerticalAlignment="Center" Grid.Column="0" Grid.Row="2"/>
<TextBox Text="{Binding Author}" Grid.Column="1" Grid.Row="2"></TextBox>
<sdk:Label HorizontalAlignment="Left" Content="图书价格：" VerticalAlignment="Center" Grid.Column="0" Grid.Row="3"/>
<TextBox Text="{Binding Price}" Grid.Column="1" Grid.Row="3"></TextBox>
<Button Content="查询" Grid.Column="1" Grid.Row="4" Width="60" Height="23" Click="Button_Click"></Button>
</Grid>
</Grid>
<Grid HorizontalAlignment="Left" Name="grid1" VerticalAlignment="Top" Width="300" Margin="20">
<Grid.RowDefinitions>
<RowDefinition Height="30"></RowDefinition>
<RowDefinition Height="30"></RowDefinition>
<RowDefinition Height="30"></RowDefinition>
<RowDefinition Height="30"></RowDefinition>
<RowDefinition Height="30"></RowDefinition>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="60"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<sdk:Label HorizontalAlignment="Left" Content="图书编号：" VerticalAlignment="Center" Grid.Column="0" Grid.Row="0"/>
<TextBox Text="{Binding ID}" Grid.Column="1" Grid.Row="0"></TextBox>
<sdk:Label HorizontalAlignment="Left" Content="图书名称：" VerticalAlignment="Center" Grid.Column="0" Grid.Row="1"/>
<TextBox Text="{Binding Name}" Grid.Column="1" Grid.Row="1"></TextBox>
<sdk:Label HorizontalAlignment="Left" Content="图书作者：" VerticalAlignment="Center" Grid.Column="0" Grid.Row="2"/>
<TextBox Text="{Binding Author}" Grid.Column="1" Grid.Row="2"></TextBox>
<sdk:Label HorizontalAlignment="Left" Content="图书价格：" VerticalAlignment="Center" Grid.Column="0" Grid.Row="3"/>
<TextBox Text="{Binding Price}" Grid.Column="1" Grid.Row="3"></TextBox>
<Button Content="查询" Grid.Column="1" Grid.Row="4" Width="60" Height="23" Click="Button_Click"></Button>
</Grid>
</Grid>
通过按钮执行调用WCF服务接口查询图书信息，按钮事件直接使用上面所写的图书门面类（BookFacade）的调用服务方法即可。
private void Button_Click(object sender, RoutedEventArgs e)
{
try
{
ThreadPool.QueueUserWorkItem(delegate(object o)
{
BookViewModel viewModel = new BookViewModel();
new BookFacade().GetBook(viewModel);
Deployment.Current.Dispatcher.BeginInvoke(() => this.DataContext = viewModel);
});
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}
{
try
{
ThreadPool.QueueUserWorkItem(delegate(object o)
{
BookViewModel viewModel = new BookViewModel();
new BookFacade().GetBook(viewModel);
Deployment.Current.Dispatcher.BeginInvoke(() => this.DataContext = viewModel);
});
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}
最终的运行如下图所示效果：
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