我如何提升属性更改属性更改？

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。 - 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 ：

（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 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:

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

You can read more on the concept of PropertyChanged here

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