wpftoolkit/ExtendedWPFToolkitSolution/Src/Samples/Samples.Infrastructure/ViewModelBase.cs

using System;
using System.ComponentModel;

namespace Samples.Infrastructure
{
    public interface IViewModel { }

    public class ViewModelBase : IViewModel, INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected virtual void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}