福州 网站设计,在线画图软件,123网页浏览器,模板之家如何免费下载由于MVVM是把View, ViewModel, Model紧紧绑定在一起的模式#xff0c;特别视图和视图模型通过实现观察者模式双向绑定和NotifyPropertyChanged事件#xff0c;似乎更加容易造成内存泄露/内存不释放。网上也有这种说法。真的是这样的吗#xff1f;我们来实际测试一下。 实际测… 由于MVVM是把View, ViewModel, Model紧紧绑定在一起的模式特别视图和视图模型通过实现观察者模式双向绑定和NotifyPropertyChanged事件似乎更加容易造成内存泄露/内存不释放。网上也有这种说法。真的是这样的吗我们来实际测试一下。 实际测试MVVM是不是容易内存泄露 为了说明问题我把MVVM搞复杂一点在ViewModel里面引用一个Singleton单例模式的Service这个Service定义如下 1: namespace SilverlightApplication1.Service 2: { 3: public class GlobalService 4: { 5: private static readonly GlobalService Instance new GlobalService(); 6: 7: static GlobalService() 8: { 9: } 10: 11: public static GlobalService GetInstance() 12: { 13: return Instance; 14: } 15: } 16: } 写一个ViewModel里面引用了Service用到了ICommand实现了INotifyPorpertyChanged接口 1: using System.ComponentModel; 2: using System.Windows.Input; 3: using SilverlightApplication1.Service; 4: 5: namespace SilverlightApplication1.MVVM 6: { 7: public class ViewModel1 : INotifyPropertyChanged 8: { 9: private GlobalService _injectSingletonService; 10: 11: public ViewModel1(GlobalService injectSingletonService) 12: { 13: Property1 test1; 14: Command1 new DelegateCommand(LoadMe, CanLoadMe); 15: 16: _injectSingletonService injectSingletonService; 17: } 18: 19: private string _property1; 20: public string Property1 21: { 22: get { return _property1; } 23: set 24: { 25: _property1 value; 26: 27: if (PropertyChanged ! null) 28: { 29: PropertyChanged(this, 30: new PropertyChangedEventArgs(Property1)); 31: } 32: } 33: } 34: 35: public ICommand Command1 { get; set; } 36: public event PropertyChangedEventHandler PropertyChanged; 37: 38: private void LoadMe(object param) 39: { 40: 41: } 42: 43: private bool CanLoadMe(object param) 44: { 45: return true; 46: } 47: } 48: } 来一个视图View绑定ViewModel有个button绑定了ICommand属性也绑定了。 1: UserControl x:ClassSilverlightApplication1.MVVM.View1 2: xmlnshttp://schemas.microsoft.com/winfx/2006/xaml/presentation 3: xmlns:xhttp://schemas.microsoft.com/winfx/2006/xaml 4: xmlns:dhttp://schemas.microsoft.com/expression/blend/2008 5: xmlns:mchttp://schemas.openxmlformats.org/markup-compatibility/2006 6: mc:Ignorabled 7: d:DesignHeight300 d:DesignWidth400 8: 9: Grid x:NameLayoutRoot BackgroundWhite 10: TextBlock Height65 HorizontalAlignmentLeft Margin57,82,0,0 NametextBlock1 Textthis is view1 VerticalAlignmentTop Width224 FontSize18 / 11: Button ContentButton Command{Binding Command1} Height28 HorizontalAlignmentLeft Margin55,130,0,0 Namebutton1 VerticalAlignmentTop Width111 / 12: TextBlock Height28 HorizontalAlignmentLeft Margin56,173,0,0 NametextBlock2 Text{Binding Property1} VerticalAlignmentTop Width114 / 13: /Grid 14: /UserControl 这个View1的界面是这样子的 View1.xaml.cs代码 1: using System.Windows.Controls; 2: using SilverlightApplication1.Service; 3: 4: namespace SilverlightApplication1.MVVM 5: { 6: public partial class View1 : UserControl 7: { 8: public View1() 9: { 10: InitializeComponent(); 11: 12: this.DataContext new ViewModel1(GlobalService.GetInstance()); 13: } 14: } 15: } 辅助类DelegateCommand源码 1: using System; 2: using System.Windows.Input; 3: 4: namespace SilverlightApplication1 5: { 6: public class DelegateCommand : ICommand 7: { 8: public event EventHandler CanExecuteChanged; 9: 10: Funcobject, bool canExecute; 11: Actionobject executeAction; 12: bool canExecuteCache; 13: 14: public DelegateCommand(Actionobject executeAction, 15: Funcobject, bool canExecute) 16: { 17: this.executeAction executeAction; 18: this.canExecute canExecute; 19: } 20: 21: #region ICommand Members 22: 23: /// summary 24: 25: /// Defines the method that determines whether the command 26: 27: /// can execute in its current state. 28: 29: /// /summary 30: 31: /// param nameparameter 32: 33: /// Data used by the command. 34: 35: /// If the command does not require data to be passed, 36: 37: /// this object can be set to null. 38: 39: /// /param 40: 41: /// returns 42: 43: /// true if this command can be executed; otherwise, false. 44: 45: /// /returns 46: 47: public bool CanExecute(object parameter) 48: { 49: 50: bool tempCanExecute canExecute(parameter); 51: 52: 53: 54: if (canExecuteCache ! tempCanExecute) 55: { 56: 57: canExecuteCache tempCanExecute; 58: 59: if (CanExecuteChanged ! null) 60: { 61: 62: CanExecuteChanged(this, new EventArgs()); 63: 64: } 65: 66: } 67: 68: 69: 70: return canExecuteCache; 71: 72: } 73: 74: 75: 76: /// summary 77: 78: /// Defines the method to be called when the command is invoked. 79: 80: /// /summary 81: 82: /// param nameparameter 83: 84: /// Data used by the command. 85: 86: /// If the command does not require data to be passed, 87: 88: /// this object can be set to null. 89: 90: /// /param 91: 92: public void Execute(object parameter) 93: { 94: 95: executeAction(parameter); 96: 97: } 98: 99: #endregion 100: } 101: } MainPage的代码 1: UserControl x:ClassSilverlightApplication1.MainPage 2: xmlnshttp://schemas.microsoft.com/winfx/2006/xaml/presentation 3: xmlns:xhttp://schemas.microsoft.com/winfx/2006/xaml 4: xmlns:dhttp://schemas.microsoft.com/expression/blend/2008 5: xmlns:mchttp://schemas.openxmlformats.org/markup-compatibility/2006 6: mc:Ignorabled 7: d:DesignHeight300 d:DesignWidth400 xmlns:sdkhttp://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk 8: 9: Grid x:NameLayoutRoot BackgroundWhite 10: Button ContentAdd view Height36 HorizontalAlignmentLeft Margin20,31,0,0 Namebutton1 VerticalAlignmentTop Width115 Clickbutton1_Click / 11: sdk:TabControl Height197 HorizontalAlignmentLeft Margin28,82,0,0 NametabControl1 VerticalAlignmentTop Width346 12: sdk:TabItem HeadertabItem1 NametabItem1 13: Grid / 14: /sdk:TabItem 15: /sdk:TabControl 16: Button ContentClose view Height35 HorizontalAlignmentLeft Margin148,32,0,0 Namebutton2 VerticalAlignmentTop Width108 Clickbutton2_Click / 17: /Grid 18: /UserControl MainPage界面主要是在Tab里面打开View1不断打开关闭打开关闭因为View1是用MVVM模式实现的看看有内存泄露 MainPage.xaml.cs就是测试代码正常情况下点击关闭tab可能GC不会立即回收内存这里为了便于测试手动加了GC.Collect。正常情况下不推荐使用GC.Collect() 1: using System; 2: using System.Windows; 3: using System.Windows.Controls; 4: using SilverlightApplication1.MVVM; 5: 6: namespace SilverlightApplication1 7: { 8: public partial class MainPage : UserControl 9: { 10: public MainPage() 11: { 12: InitializeComponent(); 13: } 14: 15: private void button1_Click(object sender, RoutedEventArgs e) 16: { 17: var v new View1(); 18: TabItem t new TabItem {Content v, Header header DateTime.Now.Second.ToString()}; 19: this.tabControl1.Items.Add(t); 20: } 21: 22: private void button2_Click(object sender, RoutedEventArgs e) 23: { 24: this.tabControl1.Items.RemoveAt(0);//view1, viewModel1并没有立即释放由GC决定何时决定。 25: 26: System.GC.Collect(); 27: System.GC.WaitForPendingFinalizers(); 28: 29: //{ 30: // FooContext context new FooContext(); 31: // context.Load(context.MyQuery); 32: //} 33: } 34: } 35: } 测试结果内存泄露和MVVM无关 我的测试结果是内存能够释放没有内存泄露问题也就是说MVVM模式和内存泄露无关。那种所谓的MVVM更容易内存泄露的说法没有什么道理。但不排除你的ViewModel和Model里面有复杂的引用关系比如你的VIewModel或者Model引用了其他的类你可能没有察觉而那些类可能是Public Static的是GC Root不释放或者是永远不释放的如MainForm引用那就复杂了。由于你的ViewModel被那些不释放的对象引用着而你却不知道那就是内存泄露了。这和MVVM没有关系。 深入思考和继续阅读 通常.NET程序的内存泄露原因 Static referencesEvent with missing unsubscriptionStatic event with missing unsubscriptionDispose method not invokedIncomplete Dispose method有关如何避免.NET程序的内存泄露请仔细阅读MSDN这两篇文章详细讲述了如何检测.NET程序内存泄露以及如何写高性能的托管程序 How to detect and avoid memory and resources leaks in .NET applicationsWriting High-Performance Managed Applications : A Primer有关.NET的自动内存管理机制、GC机制垃圾回收原理等深层次内容请仔细阅读下面的内容 买书《CLR Via C#(3rd Edition)》里面有《Memory Management》这一章专门讲述了.NET CLR的自动内存管理和垃圾回收机制CodeProject上的文章《Memory Management Misconceptions》有助你深入理解Root, Generation 0, 1… Mainz → http://www.cnblogs.com/Mainz ®: 博文是本人当时的学习笔记及知识整理由于自身局限错误在所难免敬请斧正. 博文中源码只作为例子学习参考之用不保证能运行对后果不负任何责且无任何质保如有不明请给我留言 ©: 本文版权属于博客园和本人版权基于署名 2.5 中国大陆许可协议发布欢迎转载但未经作者同意必须保留此段声明且在文章页面明显位置给出原文连接和署名Mainz包含链接不得删节否则保留追究法律责任的权利。 分类: SilverLight 转载于:https://www.cnblogs.com/Areas/archive/2011/09/23/2186621.html
