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：
namespace SilverlightApplication1.Service
2: {
class GlobalService
4: {
new GlobalService();
6:
static GlobalService()
8: {
9: }
10:
static GlobalService GetInstance()
12: {
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：
using System.ComponentModel;
using System.Windows.Input;
using SilverlightApplication1.Service;
4:
namespace SilverlightApplication1.MVVM
6: {
class ViewModel1 : INotifyPropertyChanged
8: {
private GlobalService _injectSingletonService;
10:
public ViewModel1(GlobalService injectSingletonService)
12: {
;
new DelegateCommand(LoadMe, CanLoadMe);
15:
16: _injectSingletonService = injectSingletonService;
17: }
18:
string _property1;
string Property1
21: {
return _property1; }
23: set
24: {
value;
26:
null)
28: {
this,
));
31: }
32: }
33: }
34:
public ICommand Command1 { get; set; }
event PropertyChangedEventHandler PropertyChanged;
37:
object param)
39: {
40:
41: }
42:
object param)
44: {
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。
>
8:
>
/>
/>
/>
>
>
这个View1的界面是这样子的：
View1.xaml.cs代码：
using System.Windows.Controls;
using SilverlightApplication1.Service;
3:
namespace SilverlightApplication1.MVVM
5: {
class View1 : UserControl
7: {
public View1()
9: {
10: InitializeComponent();
11:
new ViewModel1(GlobalService.GetInstance());
13: }
14: }
15: }
辅助类DelegateCommand源码：
using System;
using System.Windows.Input;
3:
namespace SilverlightApplication1
5: {
class DelegateCommand : ICommand
7: {
event EventHandler CanExecuteChanged;
9:
bool> canExecute;
object> executeAction;
bool canExecuteCache;
13:
object> executeAction,
bool> canExecute)
16: {
this.executeAction = executeAction;
this.canExecute = canExecute;
19: }
20:
#region ICommand Members
22:
/// <summary>
24:
/// Defines the method that determines whether the command
26:
/// can execute in its current state.
28:
/// </summary>
30:
32:
/// Data used by the command.
34:
/// If the command does not require data to be passed,
36:
/// this object can be set to null.
38:
/// </param>
40:
/// <returns>
42:
/// true if this command can be executed; otherwise, false.
44:
/// </returns>
46:
object parameter)
48: {
49:
bool tempCanExecute = canExecute(parameter);
51:
52:
53:
if (canExecuteCache != tempCanExecute)
55: {
56:
57: canExecuteCache = tempCanExecute;
58:
null)
60: {
61:
new EventArgs());
63:
64: }
65:
66: }
67:
68:
69:
return canExecuteCache;
71:
72: }
73:
74:
75:
/// <summary>
77:
/// Defines the method to be called when the command is invoked.
79:
/// </summary>
81:
83:
/// Data used by the command.
85:
/// If the command does not require data to be passed,
87:
/// this object can be set to null.
89:
/// </param>
91:
object parameter)
93: {
94:
95: executeAction(parameter);
96:
97: }
98:
#endregion
100: }
101: }
MainPage的代码：
>
8:
>
/>
>
>
/>
>
>
/>
>
>
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()）
using System;
using System.Windows;
using System.Windows.Controls;
using SilverlightApplication1.MVVM;
5:
namespace SilverlightApplication1
7: {
class MainPage : UserControl
9: {
public MainPage()
11: {
12: InitializeComponent();
13: }
14:
object sender, RoutedEventArgs e)
16: {
new View1();
+ DateTime.Now.Second.ToString()};
this.tabControl1.Items.Add(t);
20: }
21:
object sender, RoutedEventArgs e)
23: {
//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:
//{
// FooContext context = new FooContext();
// context.Load(context.MyQuery);
//}
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 references
- Event with missing unsubscription
- Static event with missing unsubscription
- Dispose method not invoked
- Incomplete 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 applications
- Writing 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（包含链接），不得删节，否则保留追究法律责任的权利。
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：
namespace SilverlightApplication1.Service
2: {
class GlobalService
4: {
new GlobalService();
6:
static GlobalService()
8: {
9: }
10:
static GlobalService GetInstance()
12: {
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：
using System.ComponentModel;
using System.Windows.Input;
using SilverlightApplication1.Service;
4:
namespace SilverlightApplication1.MVVM
6: {
class ViewModel1 : INotifyPropertyChanged
8: {
private GlobalService _injectSingletonService;
10:
public ViewModel1(GlobalService injectSingletonService)
12: {
;
new DelegateCommand(LoadMe, CanLoadMe);
15:
16: _injectSingletonService = injectSingletonService;
17: }
18:
string _property1;
string Property1
21: {
return _property1; }
23: set
24: {
value;
26:
null)
28: {
this,
));
31: }
32: }
33: }
34:
public ICommand Command1 { get; set; }
event PropertyChangedEventHandler PropertyChanged;
37:
object param)
39: {
40:
41: }
42:
object param)
44: {
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。
>
8:
>
/>
/>
/>
>
>
这个View1的界面是这样子的：
View1.xaml.cs代码：
using System.Windows.Controls;
using SilverlightApplication1.Service;
3:
namespace SilverlightApplication1.MVVM
5: {
class View1 : UserControl
7: {
public View1()
9: {
10: InitializeComponent();
11:
new ViewModel1(GlobalService.GetInstance());
13: }
14: }
15: }
辅助类DelegateCommand源码：
using System;
using System.Windows.Input;
3:
namespace SilverlightApplication1
5: {
class DelegateCommand : ICommand
7: {
event EventHandler CanExecuteChanged;
9:
bool> canExecute;
object> executeAction;
bool canExecuteCache;
13:
object> executeAction,
bool> canExecute)
16: {
this.executeAction = executeAction;
this.canExecute = canExecute;
19: }
20:
#region ICommand Members
22:
/// <summary>
24:
/// Defines the method that determines whether the command
26:
/// can execute in its current state.
28:
/// </summary>
30:
32:
/// Data used by the command.
34:
/// If the command does not require data to be passed,
36:
/// this object can be set to null.
38:
/// </param>
40:
/// <returns>
42:
/// true if this command can be executed; otherwise, false.
44:
/// </returns>
46:
object parameter)
48: {
49:
bool tempCanExecute = canExecute(parameter);
51:
52:
53:
if (canExecuteCache != tempCanExecute)
55: {
56:
57: canExecuteCache = tempCanExecute;
58:
null)
60: {
61:
new EventArgs());
63:
64: }
65:
66: }
67:
68:
69:
return canExecuteCache;
71:
72: }
73:
74:
75:
/// <summary>
77:
/// Defines the method to be called when the command is invoked.
79:
/// </summary>
81:
83:
/// Data used by the command.
85:
/// If the command does not require data to be passed,
87:
/// this object can be set to null.
89:
/// </param>
91:
object parameter)
93: {
94:
95: executeAction(parameter);
96:
97: }
98:
#endregion
100: }
101: }
MainPage的代码：
>
8:
>
/>
>
>
/>
>
>
/>
>
>
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()）
using System;
using System.Windows;
using System.Windows.Controls;
using SilverlightApplication1.MVVM;
5:
namespace SilverlightApplication1
7: {
class MainPage : UserControl
9: {
public MainPage()
11: {
12: InitializeComponent();
13: }
14:
object sender, RoutedEventArgs e)
16: {
new View1();
+ DateTime.Now.Second.ToString()};
this.tabControl1.Items.Add(t);
20: }
21:
object sender, RoutedEventArgs e)
23: {
//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:
//{
// FooContext context = new FooContext();
// context.Load(context.MyQuery);
//}
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 references
- Event with missing unsubscription
- Static event with missing unsubscription
- Dispose method not invoked
- Incomplete 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 applications
- Writing 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…