Silverlight杂谈（1） 跨线程访问

 在Silverlight中，使用Thread,Timer,BackgrouWorker,ThreadPool可以实现多线程开发。但是随之而来的问题是如何跨线程访问资源呢？下面先以Timer计时器为例讲解：

 示例

1、Timer.xaml

 1 <UserControl x:Class="ThreadDemo.Timer"
 2     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 3     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 4     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
 5     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
 6     mc:Ignorable="d"
 7     d:DesignHeight="300" d:DesignWidth="400">
 8 
 9     <Grid x:Name="LayoutRoot" Background="White">
10         <ScrollViewer>
11         <StackPanel x:Name="timerNum">
12             
13         </StackPanel>
14         </ScrollViewer>
15     </Grid>
16 </UserControl>

 Timer.cs

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Net;
 5 using System.Windows;
 6 using System.Windows.Controls;
 7 using System.Windows.Documents;
 8 using System.Windows.Input;
 9 using System.Windows.Media;
10 using System.Windows.Media.Animation;
11 using System.Windows.Shapes;
12 using System.Threading;
13 
14 namespace ThreadDemo
15 {
16     public partial class Timer: UserControl
17     {
18         public Timer()
19         {
20             InitializeComponent();
21             ///实例化一个Timer时间器
22             System.Threading.TimerTimer timer = new System.Threading.TimerTimer(new TimerCallback(TimerProc));
23             ///设定500毫秒后启动，每隔1000毫秒执行一次
24             timer.Change(500, 1000);
25         }
26         int flagnum;
27         public void TimerProc(object state)
28         {
29                 flagnum++;
30                 TextBlock _temptext = new TextBlock();
31                 _temptext.Text = flagnum.ToString(); 

                 timerNum.Children.Add(_temptext);
33         
34         }
35     }
36 }

F5运行程序，Visual Studio报错，跨线程访问无效。

这里使用TimerCallback委托指定希望Timer执行的方法，但是此方法不能在计时器线程上执行，所以这里就存在一个跨线程访问的问题。下面调整下代码，计时器线程将该工作委托给与该UI线程关联的Dispatcher。使用Dispatcher.BeginInvoke.

 2、Timer.cs

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Net;
 5 using System.Windows;
 6 using System.Windows.Controls;
 7 using System.Windows.Documents;
 8 using System.Windows.Input;
 9 using System.Windows.Media;
10 using System.Windows.Media.Animation;
11 using System.Windows.Shapes;
12 using System.Threading;
13 
14 namespace ThreadDemo
15 {
16     public partial class Timer: UserControl
17     {
18         public Timer()
19         {
20             InitializeComponent();
21             ///实例化一个Timer时间器
22             System.Threading.Timer timer = new System.Threading.Timer(new TimerCallback(TimerProc));
23             ///设定500毫秒后启动，每隔1000毫秒执行一次
24             timer.Change(500, 1000);
25         }
26         int flagnum;
27         public void TimerProc(object state)
28         {
29             ///在计时器的线程上使用Dispather.BeginInvoke，将计时器线程上的工作委托给UI线程关联的Dispatcher
30             this.Dispatcher.BeginInvoke(delegate
31             {
32                 flagnum++;
33                 TextBlock _temptext = new TextBlock();
34                 _temptext.Text = flagnum.ToString();
35                 timerNum.Children.Add(_temptext);
36             });
37            
38         
39         }
40     } 41 }

 F5运行成功

 

 接下来，我们再用AsyncOperation来实现跨线程访问。

3、Thread.xaml

 1 <UserControl x:Class="ThreadDemo.Thread"
 2     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 3     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 4     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
 5     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
 6     mc:Ignorable="d"
 7     d:DesignHeight="300" d:DesignWidth="400">
 8     
 9     <Grid x:Name="LayoutRoot" Background="White">
10         <ScrollViewer>
11             <StackPanel x:Name="timerNum">
12 
13             </StackPanel>
14         </ScrollViewer>
15     </Grid>16 </UserControl> 

 Thread.cs

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Net;
 5 using System.Windows;
 6 using System.Windows.Controls;
 7 using System.Windows.Documents;
 8 using System.Windows.Input;
 9 using System.Windows.Media;
10 using System.Windows.Media.Animation;
11 using System.Windows.Shapes;
12 using System.ComponentModel;
13 
14 namespace ThreadDemo
15 {
16     public partial class Thread : UserControl
17     {
18         private AsyncOperation async;
19         
20         public Thread()
21         {
22             InitializeComponent();
23             async = AsyncOperationManager.CreateOperation(null);
24             System.Threading.Thread thread = new System.Threading.Thread(TimerProc);
25             thread.Start();
26         } 
27         
28         public void TimerProc()
29         {
30            
31              async.Post(delegate
32             {
33             
34                 TextBlock _temptext = new TextBlock();
35                 _temptext.Text ="0";
36                 timerNum.Children.Add(_temptext);
37 
38             }, null);
39            
40         }
41 
42         
43     }44 } 

ok.源码下载