泛型可以使用 WPF SimpleCommand 吗？

Question

我正在使用这段代码来制作一个简单的命令：

public class SimpleCommand : ICommand
{
    public Predicate<object> CanExecuteDelegate { get; set; }
    public Action<object> ExecuteDelegate { get; set; }

    #region ICommand Members

    public bool CanExecute(object parameter)
    {
        if (CanExecuteDelegate != null)
            return CanExecuteDelegate(parameter);
        return true;// if there is no can execute default to true
    }

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

    public void Execute(object parameter)
    {
        if (ExecuteDelegate != null)
            ExecuteDelegate(parameter);
    }

    #endregion
}

这不是我写的。但我喜欢使用它。当我使用它时，它最终是这样的：

// This is the value that gets set to the command in the UI
public SimpleCommand DoSomethingCommand { get; set; }


public DoSomethingCommandConstructor()
{
    DoSomethingCommand = new SimpleCommand
                        {
                            ExecuteDelegate = x => RunCommand(x)
                        };
}

private void RunCommand(object o)
{
    // Run the command.
}

唯一的问题是 RunCommand 的参数是一个对象。我想我已经被仿制药宠坏了。我总是希望 IDE/编译器只知道我正在使用的类型是什么而不进行强制转换。

是否可以将这个 SimpleCommand 类更改为使用泛型实现？

Answer 1

当然。本来打算将您指向 Prism 的实现，但 CodePlex 源选项卡似乎无法正常工作。它看起来像：

public class SimpleCommand<T> : ICommand
{
    public Predicate<T> CanExecuteDelegate { get; set; }
    public Action<T> ExecuteDelegate { get; set; }

    #region ICommand Members

    public bool CanExecute(object parameter)
    {
        if (CanExecuteDelegate != null)
            return CanExecuteDelegate((T)parameter);
        return true;// if there is no can execute default to true
    }

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

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

    #endregion
}

顺便说一句，您在问题中对 SimpleCommand 的使用有点迂回。而不是这个：

DoSomethingCommand = new SimpleCommand
                    {
                        ExecuteDelegate = x => RunCommand(x)
                    };

你可以有：

DoSomethingCommand = new SimpleCommand
                    {
                        ExecuteDelegate = this.RunCommand
                    };

仅当您像这样进行内联工作时，指定 lambda 才真正有用：

DoSomethingCommand = new SimpleCommand
                    {
                        ExecuteDelegate = o => this.SelectedItem = o,
                        CanExecuteDelegate = o => o != null
                    };