Base types for MVVM pattern in WPF

ViewModelBase

using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows.Input;

namespace WpfApp.ViewModels
{
  class ViewModelBase : INotifyPropertyChanged
  {
    public event PropertyChangedEventHandler PropertyChanged;
    
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
      if(PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
  }

  // http://msdn.microsoft.com/en-us/magazine/dd419663.aspx
  public class RelayCommand : ICommand
  {
    readonly Action<object> _execute;
    readonly Predicate<object> _canExecute;

    public RelayCommand(Action<object> execute, Predicate<object> canExecute)
    {
      if(execute == null)
        throw new ArgumentNullException("execute");

      _execute = execute;
      _canExecute = canExecute;
    }

    public RelayCommand(Action<object> execute) : this(execute, null) { }

    public bool CanExecute(object parameter)
    {
      return _canExecute == null || _canExecute(parameter);
    }

    public event EventHandler CanExecuteChanged
    {
      add { CommandManager.RequerySuggested += value; }
      remove { CommandManager.RequerySuggested -= value; }
    }

    public void Execute(object parameter)
    {
      _execute(parameter);
    }
  }
}