WPF SimpleCommand 可以使用泛型吗？

Question

我正在使用这段代码来创建一个简单命令：

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
}

我没有写这个。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。我想我已经被泛型宠坏了。我总是希望 IDE/编译器只知道我正在使用的类型是什么，而不需要强制转换。

是否可以更改此 SimpleCommand 类以使用泛型实现？

Answer 1

当然。本来打算向您指出 Prism 的实现，但 CodePlex 源选项卡似乎不起作用。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。而不是这样：

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

您可以只具有：

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

指定 lambda 仅当您像这样内联工作时才有用：

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