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/// <summary>
/// Interface for commands to use in MVVM Pattern. It implements ICommand interface.
/// </summary>
public class RelayCommand : ICommand
{
    readonly Action<object> execute;
    readonly Func<object, bool> canExecute;

    /// <summary>
    /// CanExecuteChanged event handler.
    /// </summary>
    public event EventHandler CanExecuteChanged
    {
        add
        {
            if (canExecute != null)
                CommandManager.RequerySuggested += value;
        }
        remove
        {
            if (canExecute != null)
                CommandManager.RequerySuggested -= value;
        }
    }

    /// <summary>
    /// Constructor takes Execute and CanExecute events to register in CommandManager.
    /// </summary>
    /// <param name="execute"> Execute method as action. </param>
    /// <param name="canExecute"> CanExecute method as return boolean type. </param>
    public RelayCommand(Action<object> execute, Func<object, bool> canExecute = null)
    {
        this.execute = execute;
        this.canExecute = canExecute;
    }

    /// <summary>
    /// CanExecute method.
    /// </summary>
    /// <param name="parameter"> Method parameter. </param>
    /// <returns> Return true if can execute, else false. </returns>
    public bool CanExecute(object parameter)
    {
        return this.canExecute == null || this.canExecute(parameter);
    }

    /// <summary>
    /// Execute method.
    /// </summary>
    /// <param name="parameter"> Method parameter. </param>
    public void Execute(object parameter)
    {
        this.execute(parameter);
    }

    /// <summary>
    /// InvalidateCanExecute method forces CanExecute evaluation.
    /// </summary>
    public static void InvalidateCanExecute()
    {
        CommandManager.InvalidateRequerySuggested();
    }
}