How to Trigger an Event When a Property Value Changes in C#?

How to Raise an Event on Property Value Change

Problem Description:

You want to trigger an event whenever the value of a specific property, such as ImageFullPath1, changes. While INotifyPropertyChanged is a known solution, you prefer an event-based approach.

Answer:

To implement property change notification using events, utilize the INotifyPropertyChanged interface:

public class MyClass : INotifyPropertyChanged
{
    // ...
}

The INotifyPropertyChanged interface defines a PropertyChanged event that consumers can subscribe to. To trigger this event, implement the OnPropertyChanged method:

protected void OnPropertyChanged(PropertyChangedEventArgs e)
{
    // ...
}

protected void OnPropertyChanged(string propertyName)
{
    OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}

For the ImageFullPath1 property, update the setter as follows:

public string ImageFullPath1
{
    get { ... }
    set
    {
        if (value != ImageFullPath1)
        {
            ImageFullPath1 = value;
            OnPropertyChanged(nameof(ImageFullPath1));
        }
    }
}

Alternatively, for specific properties, you can create additional events:

protected void OnImageFullPath1Changed(EventArgs e)
{
    // ...
}

public event EventHandler ImageFullPath1Changed;

In the property setter, add OnImageFullPath1Changed(EventArgs.Empty) after OnPropertyChanged.

Improved Code with .NET 4.5:

With .NET 4.5, you can use the CallerMemberNameAttribute for a more concise implementation:

protected void OnPropertyChanged(
    [System.Runtime.CompilerServices.CallerMemberName] string propertyName = "")
{
    OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}

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