为什么BindingSource没有告诉我哪个属性已经改变了？ [英] Why does BindingSource not tell me which property has changed?

问题描述

我正在看使用数据绑定 - 最简单的事情似乎是使用BindingSource来包装我的数据对象。

然而 - 当CurrentItemChanged事件告诉我什么时候一个财产已经改变，它不告诉我哪一个 - 这是我需要的重要部分。

有没有办法找出哪个属性正在改变？

解决方案

您的数据对象需要实现INotifyPropertyChanged界面：

  public class MyObject：INotifyPropertyChanged {
 public event PropertyChangedEventHandler PropertyChanged; 
 private string textData = string.Empty; 
 
 protected void OnPropertyChanged（string propertyName）{
 if（PropertyChanged！= null）{
 PropertyChanged（this，new PropertyChangedEventArgs（propertyName））; 
} 
} 
 
 public string TextData {
 get {return textData; } 
 set {
 if（value！= textData）{
 textData = value; 
 OnPropertyChanged（TextData）; 
} 
} 
} 
} 
  

然后如果您使用BindingList，您可以使用BindingSource的ListChanged事件来查看哪个属性已更改：

  BindingList< MyObject> items = new BindingList< MyObject>（）; 
 BindingSource bs = new BindingSource（）; 
 
 protected override void OnLoad（EventArgs e）{
 base.OnLoad（e）; 
 items.Add（new MyObject（）{TextData =default text}）; 
 bs.DataSource = items; 
 bs.ListChanged + = bs_ListChanged; 
 items [0] .TextData =更改文本; 
} 
 
 void bs_ListChanged（object sender，ListChangedEventArgs e）{
 if（e.PropertyDescriptor！= null）{
 MessageBox.Show（e.PropertyDescriptor.Name ）; 
} 
} 
  

另请参阅实现INotifyPropertyChanged - 存在更好的方法？

I'm looking at using databinding - and the simplest thing to do seems to be to use a BindingSource to wrap my data objects.

However - while the CurrentItemChanged event tells me when a property has changed, it doesn't tell me which one - and that's a vital part of what I need.

Is there any way to find out which property is changing?

解决方案

Your data objects need to implement the INotifyPropertyChanged interface:

public class MyObject : INotifyPropertyChanged {
  public event PropertyChangedEventHandler PropertyChanged;
  private string textData = string.Empty;

  protected void OnPropertyChanged(string propertyName) {
    if (PropertyChanged != null) {
      PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
  }

  public string TextData {
    get { return textData; }
    set {
      if (value != textData) {
        textData = value;
        OnPropertyChanged("TextData");
      }
    }
  }
}

Then if you use BindingList, you can use the BindingSource's ListChanged event to see which property changed:

BindingList<MyObject> items = new BindingList<MyObject>();
BindingSource bs = new BindingSource();

protected override void OnLoad(EventArgs e) {
  base.OnLoad(e);
  items.Add(new MyObject() { TextData  = "default text" });
  bs.DataSource = items;
  bs.ListChanged += bs_ListChanged;
  items[0].TextData = "Changed Text";
}

void bs_ListChanged(object sender, ListChangedEventArgs e) {
  if (e.PropertyDescriptor != null) {
    MessageBox.Show(e.PropertyDescriptor.Name);
  }
}

Also see Implementing INotifyPropertyChanged - does a better way exist?

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