Feb 08, 2015 reading time 4 minutes

WPF CallMemberName for INotifyPropertyChanged

In this blog post I want to show you how to use WPF CallMemberName for INotifyPropertyChanged.

Regarding this blog post here I showed up how to implement the INotifyPropertyChanged.

Well with .Net-Framework 4.5 a new solution came up to make it even easier:

Instead of the “old” (but working) base-class

public class NotifyPropertyChangedBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged<T>(Expression<Func<T>> propertyExpression)
    {
        MemberExpression memberExpr = propertyExpression.Body as MemberExpression;
        if (memberExpr == null)
        {
            throw new ArgumentException("propertyExpression should represent access to a member");
        }

        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(memberExpr.Member.Name));
        }
    }
}

The OnPropertyChanged can be replaced with:

public class NotifyPropertyChangedBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected void NotifyPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChangedEventHandler propChanged = PropertyChanged;
        if (propChanged != null)
        {
            propChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

The CallMemberName-Attribute is automatically set to the PropertyName which calls it. So the usage in the ViewModel (or wherever you throw the event) is now easy:

public string NameToDisplay
{
    get
    {
        return _nameToDisplay;
    }
    set
    {
        _nameToDisplay = value;
        NotifyPropertyChanged();
    }
}

See: You do not need to give a func. instead you are only calling the method without any parameters.

Happy coding!

Regards