轻量级MVVM框架Stylet介绍：(9）PropertyChangedBase

ropertyChangedBase 是实现 INotifyPropertyChanged 的类型的基类，它提供了用于引发 PropertyChanged 通知的方法。

引发通知

有多种方法可以引发 PropertyChanged 通知，具体取决于您要执行的操作。

最常见的情况是让属性在每次分配到时引发通知。PropertyChangedBase提供了一个很好的实用程序方法来提供帮助：SetAndNotify。通过引用，它需要一个字段和一个要分配给该字段的值。如果字段的值 ！= 该值，则进行分配，并引发属性已更改通知。例如：

class MyClass : PropertyChangedBase
{
   private string _name;
   public string Name
   {
      get { return this._name; }
      set { SetAndNotify(ref this._name, value); }
   }

要连接到对象，必须放入视图中：
<TextBox Text="{Binding Name, UpdateSourceTrigger=PropertyChanged}"/>

如果要为当前属性以外的属性引发 PropertyChanged 通知，可以使用NotifyOfPropertyChange方法。如下所示：

class MyClass : PropertyChangedBase
{
   private string _firstName;
   public string FirstName
   {
      get { return _firstName; }
      private set
      {
         SetAndNotify(ref _firstName, value);

         // Preferred if you're using C# 6, as it provides compile-time safety
         this.NotifyOfPropertyChange(nameof(this.FullName));         
      }
   }

   private string _lastName;
   public string LastName
   {
      get { return _lastName; }
      private set
      {
         SetAndNotify(ref _lastName, value);

         // Preferred for C# 5 and below, as it provides compile-time safety
         this.NotifyOfPropertyChange(() => this.FullName);
      }
   }

   public string FullName
   {
      get { return FirstName + " " + LastName; }
   }
}

您还可以在构造函数中将内容连接在一起，如下所示：

class MyClass : PropertyChangedBase
{
   private string _firstName, _lastName;

   public MyClass()
   {
      this.Bind(s => s.FirstName, (o, e) => NotifyOfPropertyChange(nameof(FullName)));
      this.Bind(s => s.LastName, (o, e) => NotifyOfPropertyChange(nameof(FullName)));
   }

   public string FirstName
   {
      get { return _firstName; }
      private set { SetAndNotify(ref _firstName, value); }
   }

   public string LastName
   {
      get { return _lastName; }
      private set { SetAndNotify(ref _lastName, value); }
   }

   public string FullName
   {
      get { return FirstName + " " + LastName; }
   }
}

与 PropertyChanged.Fody 一起使用

PropertyChanged.Fody是一个很棒的包，它在编译时注入代码以自动为您的属性引发PropertyChanged通知，从而允许您编写非常简洁的代码。它还将找出属性之间的依赖关系，并适当地引发通知，例如：

class MyClass : PropertyChangedBase
{
   public string FirstName { get; private set; }
   public string LastName { get; private set; }
   public string FullName { get { return String.Format("{0} {1}", this.FirstName, this.LastName); } }

   public void SomeMethod()
   {
      // PropertyChanged notifications are automatically raised for both FirstName and FullName
      this.FirstName = "Fred";
   }