我如何提升属性更改属性更改？ [英] How can i RaisePropertyChanged on property change?

问题描述

在这里我添加了一个模型给我的viewmodel ...

  public dal.UserAccount User {
 get 
 {
 return _user; 
} 
 set 
 {
 _user = value; 
 RaisePropertyChanged（String.Empty）; 
} 
} 
  

我处理属性更改事件...

 公共事件PropertyChangedEventHandler PropertyChanged; 
 private void RaisePropertyChanged（string propertyName）
 {
 if（this.PropertyChanged！= null）
 this.PropertyChanged（this，new PropertyChangedEventArgs（propertyName））; 
} 
  

这是我使用的绑定。

 < TextBox Text ={Binding User.firstname，Mode = TwoWay，ValidatesOnDataErrors = True，UpdateSourceTrigger = PropertyChanged}/> 
  

问题是propertychange事件在更新视图时不触发？任何人都可以告诉我我做错了什么...

解决方案

PropertyChanged用于通知UI，该模型。
由于您正在更改用户对象的内部属性 - 用户属性本身不是因此更改了PropertyChanged事件。

第二 - 您的模型应该实现 INotifyPropertyChanged 界面。 - 换句话说，确保 UserAccount 实现INotifyPropertyChanged，否则更改 firstname 不会影响视图。 >

另一件事：

RaisePropertyChanged应该接收的参数是属性的名称改变。所以在你的情况下：

更改：

RaisePropertyChanged（String.Empty）; / p>

到

RaisePropertyChanged（User）;

从 MSDN ：

PropertyChanged事件可以指示对象中的所有属性都通过使用null或String.Empty作为PropertyChangedEventArgs中的属性名称而更改。

（无需刷新本例中的所有属性）

您可以阅读更多关于 PropertyChanged 的概念 here

Here I added a model to my viewmodel...

public dal.UserAccount User  {
  get
  {
    return _user;
  }
  set
  {
    _user = value;
    RaisePropertyChanged(String.Empty); 
   }
}

I handle property change event...

public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string propertyName)
{
  if (this.PropertyChanged != null)
    this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}

This is the binding i use.

<TextBox Text="{Binding User.firstname, Mode=TwoWay, ValidatesOnDataErrors=True, UpdateSourceTrigger=PropertyChanged}" />

Problem is propertychange event is not trigger on updating view ? Can anybody tell me what i am doing wrong...

解决方案

PropertyChanged is used to notify the UI that something has been changed in the Model. Since you're changing an inner property of the User object - the User property itself is not changed and therefore the PropertyChanged event isn't raised.

Second - your Model should implement the INotifyPropertyChanged interface. - In other words make sure UserAccount implements INotifyPropertyChanged, otherwise changing the firstname will not affect the view either.

Another thing:

The parameter RaisePropertyChanged should receive is the Name of the property that has changed. So in your case:

Change:
RaisePropertyChanged(String.Empty);

To
RaisePropertyChanged("User");

From MSDN:

The PropertyChanged event can indicate all properties on the object have changed by using either null or String.Empty as the property name in the PropertyChangedEventArgs.

(No need to refresh all the Properties in this case)

You can read more on the concept of PropertyChanged here

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