什么叫INotifyPropertyChanged的的PropertyChanged事件的最好方法是什么？ [英] What's the best way to call INotifyPropertyChanged's PropertyChanged event?

问题描述

在实现INotifyPropertyChanged接口，你是负责调用PropertyChanged事件每每次一个属性在类更新。

When you implement the INotifyPropertyChanged interface, you're responsible for calling the PropertyChanged event each and everytime a property is updated in the class.

这通常会导致以下code：

This typically leads to the following code :

    public class MyClass: INotifyPropertyChanged

        private bool myfield;
        public bool MyField
        {
            get { return myfield; }
            set
            {
                if (myfield == value)
                    return;
                myfield = value;
                OnPropertyChanged(new PropertyChangedEventArgs("MyField"));
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged(PropertyChangedEventArgs e)
        {
            PropertyChangedEventHandler h = PropertyChanged;
            if (h != null)
                h(this, e);
        }
   }

这是 12行每个属性。

这将是非常简单的，如果一个人能装点这样的自动属性：

It would be so much simpler if one was able to decorate automatic properties like this :

[INotifyProperty]
public double MyField{ get; set; }

但不幸的是，这是不可能的（见这个帖子 MSDN上的例如）

But unfortunately this is not possible (see this post on msdn for example)

我怎样才能减少每财产所需的code量？

How can I reduce the amount of code needed per property?

推荐答案

其实，这是只有3-4行的每个属性的;其他线的摊销的对所有通知属性：

Actually, it's only 3-4 lines per property; the other lines are amortized over all "notifying" properties:

class Person : INotifyPropertyChanged
{
    #region INotifyPropertyChanged: Shared bit
    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, e);
    }
    #endregion

    private string _firstName;
    public string FirstName
    {
        get { return _firstName; }
        set
        {
            if (_firstName == value)
                return;
            _firstName = value;
            OnPropertyChanged(new PropertyChangedEventArgs("FirstName"));
        }
    }

    // Ditto for other properties
}

您可以尝试像下面这股更多的负载：

You could try something like the following, which shares some more of the load:

private string _firstName;
public string FirstName
{
    get { return _firstName; }
    set { SetNotifyingProperty("FirstName", ref _firstName, value); }
}
private void SetNotifyingProperty<T>(string propertyName,
                                     ref T field, T value)
{
    if (value.Equals(field))
        return;
    field = value;
    OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}

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