内容摘要：

这是我在某个客户那边讲课的时候遇到一个小问题，在ViewModel中创建的一个Timer，并不会被自动停止，即便使用该ViewModel的View已经被关闭了。这个问题的原因在于Timer的特殊工作机制，它是运行在一个独立的工作线程的，除非明确地停止他，或者整个程序关闭了，它才会停止。这一讲中，我通过实例重现了这个问题，然后提供了一个可行的解决方法。

视频地址：

http://www.tudou.com/programs/view/uO4b2j0N4L8/

示例代码：

备注：该范例使用了MvvmLight作为MVVM框架，请自行安装

Model：

using System;
using System.Diagnostics;
using System.Linq;namespace SilverlightApplicationSample
{public class DataService{public static Customer[] GetCustomers(){Debug.WriteLine(string.Format("[{0}]正在调用数据服务",DateTime.Now));var rnd = new Random();return Enumerable.Range(1, rnd.Next(100)).Select(x => new Customer(){CompanyName = "Company " + x.ToString()}).ToArray();}}public class Customer{public string CompanyName { get; set; }}
}

using System;
using System.Windows.Threading;
using GalaSoft.MvvmLight;namespace SilverlightApplicationSample
{/// <summary>/// 使用MVVMLight实现的MVVM ViewModel/// </summary>public class CustomerWindowViewModel : ViewModelBase{/// <summary>/// 这个方法也不会自动调用/// </summary>public override void Cleanup(){base.Cleanup();timer.Stop();}DispatcherTimer timer = null;public CustomerWindowViewModel(){//正常情况下的绑定//Customers = DataService.GetCustomers();//使用定时器调用服务timer = new DispatcherTimer();timer.Interval = TimeSpan.FromSeconds(1);timer.Tick += (o, a) =>{Customers = DataService.GetCustomers();};timer.Start();}private Customer[] _Customers;public Customer[] Customers{get { return _Customers; }set{if (_Customers != value){_Customers = value;RaisePropertyChanged("Customers");}}}}
}

View：

<controls:ChildWindow x:Class="SilverlightApplicationSample.CustomerWindow"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:controls="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls"Width="400"Height="300"Title="CustomerWindow"xmlns:local="clr-namespace:SilverlightApplicationSample"><controls:ChildWindow.DataContext><local:CustomerWindowViewModel></local:CustomerWindowViewModel></controls:ChildWindow.DataContext><Grid x:Name="LayoutRoot"Margin="2"><Grid.RowDefinitions><RowDefinition /><RowDefinition Height="Auto" /></Grid.RowDefinitions><ListBox ItemsSource="{Binding Customers}"DisplayMemberPath="CompanyName"></ListBox><Button x:Name="CancelButton"Content="Cancel"Click="CancelButton_Click"Width="75"Height="23"HorizontalAlignment="Right"Margin="0,12,0,0"Grid.Row="1" /><Button x:Name="OKButton"Content="OK"Click="OKButton_Click"Width="75"Height="23"HorizontalAlignment="Right"Margin="0,12,79,0"Grid.Row="1" /></Grid>
</controls:ChildWindow>

Page：

using System.Windows;
using System.Windows.Controls;namespace SilverlightApplicationSample
{public partial class MainPage : UserControl{public MainPage(){InitializeComponent();}private void Button_Click(object sender, RoutedEventArgs e){var window = new CustomerWindow();window.Closed += (o, a) =>{var vm = window.DataContext as CustomerWindowViewModel;vm.Cleanup();};window.Show();}}
}