laatzen/Common/TestUI/ViewModels/BaseVM.cs

namespace TestUI.ViewModels
{
    using System;
    using System.ComponentModel;
    using System.Windows.Input;

    public abstract class BaseVM : INotifyPropertyChanged, IDisposable
    {
        public event PropertyChangedEventHandler PropertyChanged;

        protected BaseVM()
        {
            App.Close += this.Dispose;
        }

        protected void NotifyPropertyChanged(string property)
        {
            this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(property));
        }

        protected void Set<T>(ref T oldValue, T newValue, string property)
        {
            oldValue = newValue;

            this.NotifyPropertyChanged(property);
        }

        public void Dispose()
        {
            App.Close -= this.Dispose;
        }

        internal class Command : ICommand
        {
            private readonly Action commandHandler;

            public Command(Action commandHandler)
            {
                this.commandHandler = commandHandler;
            }

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

            public bool CanExecute(object parameter)
            {
                return this.commandHandler != null;
            }

            public void Execute(object parameter)
            {
                this.commandHandler?.Invoke();
            }
        }

        internal class Command<T> : ICommand
        {
            private readonly Action<T> commandCallback;

            public Command(Action<T> commandCallback)
            {
                this.commandCallback = commandCallback;
            }

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

            public bool CanExecute(object parameter)
            {
                return this.commandCallback != null;
            }

            public void Execute(object parameter)
            {
                this.commandCallback?.Invoke(parameter is T value ? value : default(T));
            }
        }
    }
}