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

Prism 5实现:

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

    protected virtual bool SetProperty<T>(ref T storage,
                                          T value,
                                          [CallerMemberName] string propertyName = null)
    {
        if (object.Equals(storage, value)) return false;

        storage = value;
        this.OnPropertyChanged(propertyName);

        return true;
    }

    protected void OnPropertyChanged(string propertyName)
    {
        var eventHandler = this.PropertyChanged;
        if (eventHandler != null)
        {
            eventHandler(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    protected void OnPropertyChanged<T>(Expression<Func<T>> propertyExpression)
    {
        var propertyName = PropertySupport.ExtractPropertyName(propertyExpression);
        this.OnPropertyChanged(propertyName);
    }
}

public static class PropertySupport
{
    public static string ExtractPropertyName<T>(Expression<Func<T>> propertyExpression)
    {
        if (propertyExpression == null)
        {
            throw new ArgumentNullException("propertyExpression");
        }

        var memberExpression = propertyExpression.Body as MemberExpression;
        if (memberExpression == null)
        {
            throw new ArgumentException("The expression is not a member access expression.", "propertyExpression");
        }

        var property = memberExpression.Member as PropertyInfo;
        if (property == null)
        {
            throw new ArgumentException("The member access expression does not access a property.", "propertyExpression");
        }

        var getMethod = property.GetMethod;
        if (getMethod.IsStatic)
        {
            throw new ArgumentException("The referenced property is a static property.", "propertyExpression");
        }

        return memberExpression.Member.Name;
    }
}

其他回答

我把它作为一个片段保存下来。c# 6为调用处理程序添加了一些不错的语法。

// INotifyPropertyChanged

public event PropertyChangedEventHandler PropertyChanged;

private void Set<T>(ref T property, T value, [CallerMemberName] string propertyName = null)
{
    if (EqualityComparer<T>.Default.Equals(property, value) == false)
    {
        property = value;
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

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)

如果你在。net 4.5中使用动态,你不需要担心INotifyPropertyChanged。

dynamic obj = new ExpandoObject();
obj.Name = "John";

如果Name被绑定到某个控件,它就可以正常工作。

我真的很喜欢Marc的解决方案,但我认为可以稍微改进一下,以避免使用“魔法字符串”(不支持重构)。与其将属性名作为字符串使用,不如将其创建为lambda表达式:

private string name;
public string Name
{
    get { return name; }
    set { SetField(ref name, value, () => Name); }
}

只需要在Marc的代码中添加以下方法,就可以了:

protected virtual void OnPropertyChanged<T>(Expression<Func<T>> selectorExpression)
{
    if (selectorExpression == null)
        throw new ArgumentNullException("selectorExpression");
    MemberExpression body = selectorExpression.Body as MemberExpression;
    if (body == null)
        throw new ArgumentException("The body must be a member expression");
    OnPropertyChanged(body.Member.Name);
}

protected bool SetField<T>(ref T field, T value, Expression<Func<T>> selectorExpression)
{
    if (EqualityComparer<T>.Default.Equals(field, value)) return false;
    field = value;
    OnPropertyChanged(selectorExpression);
    return true;
}

顺便说一句,这是受到这篇博客文章的启发。

我建议使用ReactiveProperty。 这是除了Fody之外最短的方法。

public class Data : INotifyPropertyChanged
{
    // boiler-plate
    ...
    // props
    private string name;
    public string Name
    {
        get { return name; }
        set { SetField(ref name, value, "Name"); }
    }
}

而不是

public class Data
{
    // Don't need boiler-plate and INotifyPropertyChanged

    // props
    public ReactiveProperty<string> Name { get; } = new ReactiveProperty<string>();
}

(文档)