[Silverlight入门系列]使用MVVM模式(4)：Prism的NotificationObject自动实现INotifyPropertyChanged接...

public abstract class NotificationObject : INotifyPropertyChanged 2 { 3 protected NotificationObject(); 4 protected void RaisePropertyChanged<T>(Expression<Func<T>> propertyExpression); 6 protected void RaisePropertyChanged(params string [] propertyNames); 7 protected virtual void RaisePropertyChanged(string propertyName); 8 }

提供了几个很方面的接口，调用更方便了，例如：

public string ModelName 2 { 3 get { return _ModelName; } 4 set { 6 _ModelName = value; 7 RaisePropertyChanged("ModelName" ); 9 10 } 11 }

第二个RaisePropertyChanged<T>(Expression<Func<T>> propertyExpression);是一个表达式，编译为一个Func委托，返回一个T类型。

例如可以这样用：

this.RaisePropertyChanged(() => this.MyDataSummary);

ViewModel的INotifyPropertyChanged接口和Model的INotifyPropertyChanged接口

ViewModel和Model它们二者都实现INotifyPropertyChanged接口并不矛盾。用途不一样。例如一个ViewModel可以包含多个其它的ViewModel，而它们有一个整体的HasChanged属性来标识是否有改变。这个时候这个整体的ViewModel的HasChanged属性就可以用整体的INotifyPropertyChanged，而局部的INotifyPropertyChanged实现了这个整体的INotifyPropertyChanged。看个例子：

using Microsoft.Practices.Prism.ViewModel; 2 public class MyViewModel3: NotificationObject 4 { 5 public MyModel MyModelData { get; set ; } 6 public MyModel2 MyModelData2 { get; set ; } 7 public bool HasChanges { get; set ; } 9 public bool CanSave { get; set ; } 10 public MyViewModel3(MyModel model, MyModel2 model2) 12 { 13 MyModelData = model; 14 MyModelData2 = model2; 15 model.PropertyChanged += this .OnPropertyChanged; 17 } 18 private void OnPropertyChanged(object sender, PropertyChangedEventArgs args) 20 { 21 if (args.PropertyName == "Name" ) 22 { 23 this.HasChanges = true ; 24 this.RaisePropertyChanged(() => this .CanSave); 25 } 26 } 27 } 28 public class MyModel2 : INotifyPropertyChanged 30 { 31 public event PropertyChangedEventHandler PropertyChanged; 32 public int ModelID { get; set ; } 34 private string _ModelName; 36 public string ModelName 37 { 38 get { return _ModelName; } 39 set { 41 _ModelName = value; 42 if (PropertyChanged != null ) 44 { 45 PropertyChanged(this, new PropertyChangedEventArgs("ModelName" )); 46 } 47 } 48 } 49 } 50 public class MyModel : INotifyPropertyChanged 52 { 53 public event PropertyChangedEventHandler PropertyChanged; 54 public int ModelID { get; set ; } 56 private string _ModelName; 58 public string ModelName 59 { 60 get { return _ModelName; } 61 set { 63 _ModelName = value; 64 if (PropertyChanged != null ) 66 { 67 PropertyChanged(this, new PropertyChangedEventArgs("ModelName" )); 68 } 69 } 70 } 71 }

此外，Validation既可以放在Model里面也可以放在ViewModel里面，看你的规则是否简单，是否涉及业务逻辑，有的复杂的业务逻辑validation的需要调用后台service的建议放到ViewModel中去做。