INotifyPropertyChanged in UserControl

Question

I have a custom control which is inherited from TextBox control. I would like to implement the INotifyPropertyChanged interface in my custom control.

public class CustomTextBox : TextBox, INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    protected void NotifyPropertyChanged(string info)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(info));
    }
}

My problem is when I try to raised a PropertyChanged event the PropertyChanged event handler is always null.

Anybody can help me?

Answer 1

the PropertyChanged event handler is alwas null.

This will always be true until something subscribes to the PropertyChanged event.

Typically, if you're making a custom control, however, you wouldn't use INotifyPropertyChanged. In this scenario, you'd make a Custom Dependency Property instead. Normally, the dependency objects (ie: controls) will all use Dependency Properties, and INPC is used by the classes which become the DataContext of these objects. This allows the binding system to work properly.