who added the method in to "PropertyChanged"? Questions about using "INotifyPropertyChanged"

Question

please see the picture, who added the method in to "PropertyChanged", I didn't do anything , but "PropertyChangedcan" be called , and "PropertyChanged" is not null value

Answer 1

Hi,@43061275. I have not been able to reproduce your problem. Could you show minimal code that reproduces the problem?
xaml:

 <Window.DataContext>  
    <local:Person/>  
</Window.DataContext>  
<StackPanel>  
    <TextBox x:Name="tb" Text="{Binding PersonName,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Height="50" Background="AliceBlue"/>  
    <TextBlock x:Name="tb1" Text="{Binding PersonName,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Height="50" Background="AliceBlue"/>  
   
</StackPanel>  

codebehind:

 public class Person: INotifyPropertyChanged  
  {  
    private string name = "hello";  
    public string PersonName  
    {  
      get { return name; }  
      set  
      {  
        name = value;  
        ChangeProperty();  
      }  
    }  
    public event PropertyChangedEventHandler PropertyChanged;  
    protected void ChangeProperty([CallerMemberName] string name = null)  
    {  
      PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));  
    }  
  }  

The result:

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Answer 2

When you implement INotifyPropertyChanged Visual Studio adds PropertyChangedEventHandler and OnPropertyChanged.

To see how it's done, add a new class to your project, implement INotifyPropertyChanged and Visual Studio will indicated missing members and will offer to create them for you.

Note I'm curious why your code does not appear as follows which uses CallerMemberName.

public class VendorModel : INotifyPropertyChanged  
{  
	private readonly CollectionView _vendorEntries;  
	private string _vendorEntry;  
  
	public VendorModel()  
	{  
		IReadOnlyList<Vendor> list = References.Vendors();  
		_vendorEntries = new CollectionView(list);  
	}  
  
	public CollectionView VendorEntries => _vendorEntries;  
  
	public string VendorEntry  
	{  
		get => _vendorEntry;  
		set  
		{  
  
			if (_vendorEntry == value)  
			{  
				return;  
			}  
  
			_vendorEntry = value;  
  
			OnPropertyChanged();  
		}  
	}  
  
	public event PropertyChangedEventHandler PropertyChanged;  
	protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)  
	{  
		PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));  
	}  
}