windows-8 - 有没有 WinRT iCommand/CommandBinding 实现示例？

Question

将命令抽象到 View 模型中对于 XAML/MVVM 项目来说是一种很有值(value)的做法。我明白了。而且，我在 WinRT 中看到了 ICommand；但是，我们如何实现呢？我还没有找到真正有效的样本。有人知道吗？

Answer 1

我一直最喜欢的是 Microsoft 模式和实践团队提供的 DelegateCommand。它允许您创建键入的命令:

MyCommand = new DelegateCommand<MyEntity>(OnExecute);
...
private void OnExecute(MyEntity entity)
{...}

它还提供了一种引发 CanExecuteChanged 事件的方法(禁用/启用命令)

MyCommand.RaiseCanExecuteChanged();

这是代码:

public class DelegateCommand<T> : ICommand
{
    private readonly Func<T, bool> _canExecuteMethod;
    private readonly Action<T> _executeMethod;

    #region Constructors

    public DelegateCommand(Action<T> executeMethod)
        : this(executeMethod, null)
    {
    }

    public DelegateCommand(Action<T> executeMethod, Func<T, bool> canExecuteMethod)
    {
        _executeMethod = executeMethod;
        _canExecuteMethod = canExecuteMethod;
    }

    #endregion Constructors

    #region ICommand Members

    public event EventHandler CanExecuteChanged;

    bool ICommand.CanExecute(object parameter)
    {
        try
        {
            return CanExecute((T)parameter);
        }
        catch { return false; }
    }

    void ICommand.Execute(object parameter)
    {
        Execute((T)parameter);
    }

    #endregion ICommand Members

    #region Public Methods

    public bool CanExecute(T parameter)
    {
        return ((_canExecuteMethod == null) || _canExecuteMethod(parameter));
    }

    public void Execute(T parameter)
    {
        if (_executeMethod != null)
        {
            _executeMethod(parameter);
        }
    }

    public void RaiseCanExecuteChanged()
    {
        OnCanExecuteChanged(EventArgs.Empty);
    }

    #endregion Public Methods

    #region Protected Methods

    protected virtual void OnCanExecuteChanged(EventArgs e)
    {
        var handler = CanExecuteChanged;
        if (handler != null)
        {
            handler(this, e);
        }
    }

    #endregion Protected Methods
}