/* * This has been taken over from Josh Smith's MSDN-mag article on MVVM * * -> http://msdn.microsoft.com/en-us/magazine/dd419663.aspx * */ using System; using System.Diagnostics; using System.Windows.Input; namespace Nova.Studio { /// <summary> /// A command whose sole purpose is to relay its functionality to other objects by invoking delegates. /// The default return value for the CanExecute method is 'true'. /// </summary> public class RelayCommand : ICommand { #region Fields protected readonly Action<object> _execute; protected readonly Predicate<object> _canExecute; #endregion #region Constructors /// <summary> /// Creates a new command that can always execute. /// </summary> /// <param name="execute">The execution logic.</param> public RelayCommand(Action<object> execute) : this(execute, null) { } /// <summary> /// Creates a new command. /// </summary> /// <param name="execute">The execution logic.</param> /// <param name="canExecute">The execution status logic.</param> public RelayCommand(Action<object> execute, Predicate<object> canExecute) { if (execute == null) throw new ArgumentNullException("execute"); _execute = execute; _canExecute = canExecute; } #endregion #region ICommand Members [DebuggerStepThrough] 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); } #endregion } }
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