试图了解INotifyPropertyChanged [英] Trying to understand INotifyPropertyChanged

问题描述

几个（新手）问题：

1）我看到很多

public Person SelectedPerson { get; set; } 

我假设这不会改变属性？

I am assuming this does NOT fire a property change?

所以，如果我想这样做，我必须提供以下内容？

So, if I want to do so, I must provide the following?

    private Person selectedPerson;
    public Person SelectedPerson
    {
        get
        {
            return this.selectedPerson;
        }
        set
        {
            if ((this.selectedPerson != value))
            {
                this.selectedPerson = value;
                base.OnPropertyChanged("SelectedPerson");
                // Note: Using ViewModelBase

            }
        }
    }

2）如果我有以下条件：

2) If I have the following:

    public bool CanDeletePerson
    {
        get
        {
            return SelectedPerson != null;
        }
    }

以及XAML

< Button IsEnabled="{Binding CanDeletePerson}" 
Command="{Binding DeletePersonCommand}"> Delete </ Button >

如何让它重新评估CanDeletePerson属性？
基本上，它最初被禁用，但是当我点击网格并将行移动到行时，SelectedPerson IS被更新，但CanDeletePerson没有获得更新的值，那么如何让它实际检查值再次？

How do I get it to re-evaluate the CanDeletePerson property? Basically, it is initially disabled, but when I click on the grid and move row to row, the SelectedPerson IS being updated, but the CanDeletePerson is NOT getting the updated value, so how do I get it to actually check the value again?

3）我看到

...取决于是否有已订阅事件

... depends on whether anything has subscribed to the event

您如何订阅该活动？

推荐答案

1. 正确 - 不触发



2. code> CanDeletePerson 重新评估，您可以在 CanDeletePerson 中调用PropertyChanged，如此

1. Correct - that does not fire

2. Yes, to have CanDeletePerson reevaluated, you can raise PropertyChanged on CanDeletePerson, like so

    set
    { 
        if ((this.selectedPerson != value))
        { 
            this.selectedPerson = value; 
            base.OnPropertyChanged("SelectedPerson"); 
            base.OnPropertyChanged("CanDeletePerson");
        }
    }

像任何正常的事件一样，但如果你使用WPF，您通常不需要明确订阅

Like any normal event, but if you're using WPF, you typically don't need to subscribe explicitly

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