微软应该为INotifyPropertyChanged实现一些时髦的东西,就像在自动属性中,只需要指定{get;设置;通知;} 我认为这样做很有意义。或者做这个手术有什么并发症吗?

我们能在属性中实现类似notify的东西吗。在你的类中实现INotifyPropertyChanged是否有一个优雅的解决方案,或者唯一的方法是在每个属性中引发PropertyChanged事件。

如果不是,我们可以写一些东西来自动生成一段代码来引发PropertyChanged事件?


当前回答

根据Thomas的回答,这是从Marc的回答改编而来的,我把反射属性更改代码变成了一个基类:

public abstract class PropertyChangedBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null) 
            handler(this, new PropertyChangedEventArgs(propertyName));
    }

    protected void OnPropertyChanged<T>(Expression<Func<T>> selectorExpression)
    {
        if (selectorExpression == null)
            throw new ArgumentNullException("selectorExpression");
        var me = selectorExpression.Body as MemberExpression;

        // Nullable properties can be nested inside of a convert function
        if (me == null)
        {
            var ue = selectorExpression.Body as UnaryExpression;
            if (ue != null)
                me = ue.Operand as MemberExpression;
        }

        if (me == null)
            throw new ArgumentException("The body must be a member expression");

        OnPropertyChanged(me.Member.Name);
    }

    protected void SetField<T>(ref T field, T value, Expression<Func<T>> selectorExpression, params Expression<Func<object>>[] additonal)
    {
        if (EqualityComparer<T>.Default.Equals(field, value)) return;
        field = value;
        OnPropertyChanged(selectorExpression);
        foreach (var item in additonal)
            OnPropertyChanged(item);
    }
}

用法与Thomas的答案相同,只是您可以传递要通知的其他属性。这对于处理需要在网格中刷新的计算列是必要的。

private int _quantity;
private int _price;

public int Quantity 
{ 
    get { return _quantity; } 
    set { SetField(ref _quantity, value, () => Quantity, () => Total); } 
}
public int Price 
{ 
    get { return _price; } 
    set { SetField(ref _price, value, () => Price, () => Total); } 
}
public int Total { get { return _price * _quantity; } }

我有这个驱动存储在BindingList中的项的集合,通过DataGridView暴露。它消除了我对网格进行手动Refresh()调用的需要。

其他回答

根据Thomas的回答,这是从Marc的回答改编而来的,我把反射属性更改代码变成了一个基类:

public abstract class PropertyChangedBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null) 
            handler(this, new PropertyChangedEventArgs(propertyName));
    }

    protected void OnPropertyChanged<T>(Expression<Func<T>> selectorExpression)
    {
        if (selectorExpression == null)
            throw new ArgumentNullException("selectorExpression");
        var me = selectorExpression.Body as MemberExpression;

        // Nullable properties can be nested inside of a convert function
        if (me == null)
        {
            var ue = selectorExpression.Body as UnaryExpression;
            if (ue != null)
                me = ue.Operand as MemberExpression;
        }

        if (me == null)
            throw new ArgumentException("The body must be a member expression");

        OnPropertyChanged(me.Member.Name);
    }

    protected void SetField<T>(ref T field, T value, Expression<Func<T>> selectorExpression, params Expression<Func<object>>[] additonal)
    {
        if (EqualityComparer<T>.Default.Equals(field, value)) return;
        field = value;
        OnPropertyChanged(selectorExpression);
        foreach (var item in additonal)
            OnPropertyChanged(item);
    }
}

用法与Thomas的答案相同,只是您可以传递要通知的其他属性。这对于处理需要在网格中刷新的计算列是必要的。

private int _quantity;
private int _price;

public int Quantity 
{ 
    get { return _quantity; } 
    set { SetField(ref _quantity, value, () => Quantity, () => Total); } 
}
public int Price 
{ 
    get { return _price; } 
    set { SetField(ref _price, value, () => Price, () => Total); } 
}
public int Total { get { return _price * _quantity; } }

我有这个驱动存储在BindingList中的项的集合,通过DataGridView暴露。它消除了我对网格进行手动Refresh()调用的需要。

反射:利用反射的思想:

class ViewModelBase : INotifyPropertyChanged {

    public event PropertyChangedEventHandler PropertyChanged;

    bool Notify<T>(MethodBase mb, ref T oldValue, T newValue) {

        // Get Name of Property
        string name = mb.Name.Substring(4);

        // Detect Change
        bool changed = EqualityComparer<T>.Default.Equals(oldValue, newValue);

        // Return if no change
        if (!changed) return false;

        // Update value
        oldValue = newValue;

        // Raise Event
        if (PropertyChanged != null) {
            PropertyChanged(this, new PropertyChangedEventArgs(name));
        }//if

        // Notify caller of change
        return true;

    }//method

    string name;

    public string Name {
        get { return name; }
        set {
            Notify(MethodInfo.GetCurrentMethod(), ref this.name, value);
        }
    }//method

}//class

看这里:http://dotnet-forum.de/blogs/thearchitect/archive/2012/11/01/die-optimale-implementierung-des-inotifypropertychanged-interfaces.aspx

它是用德语写的,但你可以下载ViewModelBase.cs。cs-File中的所有注释都是用英语写的。

使用这个ViewModelBase-Class,可以实现类似于众所周知的依赖属性的可绑定属性:

public string SomeProperty
{
    get { return GetValue( () => SomeProperty ); }
    set { SetValue( () => SomeProperty, value ); }
}

我认为人们应该多关注一下表现;当有很多对象需要绑定时(想想有10,000多行的网格),或者对象的值经常变化时(实时监控应用程序),它确实会影响UI。

我把这里和其他地方找到的各种实现进行了比较;查看INotifyPropertyChanged实现的性能比较。


下面是测试结果

我写了一篇文章来帮助你(https://msdn.microsoft.com/magazine/mt736453)。你可以使用SolSoft。DataBinding NuGet包。然后你可以这样写代码:

public class TestViewModel : IRaisePropertyChanged
{
  public TestViewModel()
  {
    this.m_nameProperty = new NotifyProperty<string>(this, nameof(Name), null);
  }

  private readonly NotifyProperty<string> m_nameProperty;
  public string Name
  {
    get
    {
      return m_nameProperty.Value;
    }
    set
    {
      m_nameProperty.SetValue(value);
    }
  }

  // Plus implement IRaisePropertyChanged (or extend BaseViewModel)
}

好处:

基类是可选的 没有对每个“设定值”进行反思 可以具有依赖于其他属性的属性,并且它们都自动引发适当的事件(本文有一个这样的示例)