试图了解INotifyPropertyChanged的 [英] Trying to understand INotifyPropertyChanged

问题描述

若干（新手）问题：

1）我看到了很多的

 公众人物SelectedPerson {搞定;组; } 
  

我假定这不火属性更改？

所以，如果我想这样做，我必须提供以下

 私募人士selectedPerson？; 
公众人物SelectedPerson 
 {
得到
 {
返回this.selectedPerson; 
} 
组
 {
如果（（this.selectedPerson =值）！）
 {
 this.selectedPerson =价值; 
 base.OnPropertyChanged（SelectedPerson）; 
 //注意：使用ViewModelBase 
 
} 
} 
} 
  

2）如果我有以下几点：

 公共BOOL CanDeletePerson 
 {
得到
 {
返回SelectedPerson！= NULL; 
} 
} 
  

和也在XAML

 <按钮IsEnabled ={结合CanDeletePerson}
命令={结合DeletePersonCommand}>删除< /按钮> 
  

我如何得到它的重新评估CanDeletePerson财产？
基本上，它最初是禁用的，但是当我点击电网和移动行与行的SelectedPerson正在更新，但CanDeletePerson没有得到更新的价值，所以我怎么得到它实际上是检查值再？

3）我看

...取决于是否什么已订阅的事件。

你如何订阅事件？

解决方案

1. 正确 - 不火



2. 是的，有 CanDeletePerson 重新评估，可以在 CanDeletePerson ，像这样

    设置
    {
   如果（（this.selectedPerson =值）！）
    {
    this.selectedPerson =价值; 
    base.OnPropertyChanged（SelectedPerson）; 
    base.OnPropertyChanged（CanDeletePerson）; 
   } 
   } 
     




3. 像任何正常事件，但如果你'再使用WPF，你通常不需要明确订阅

Several (newbie) questions:

1) I see a lot of

public Person SelectedPerson { get; set; }

I am assuming this does NOT fire a property change?

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) If I have the following:

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

and also in the XAML

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

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) I see

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

How do you subscribe to the event?

解决方案

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");
           }
       }
   

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

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