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wpf simplecommand是否可以与泛型一起使用?

command generics wpf c#

Vaccano · 技术社区 · 14 年前

我正在使用此代码生成一个简单的命令:

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
}

我没有写这个。但我喜欢用它。当我使用它时,结果是这样的:

// 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。我想我被仿制药宠坏了。我总是希望IDE/编译器知道我使用的类型是OutCasting。

是否可以使用泛型更改要实现的SimpleCommand类?

1 回复 | 直到 13 年前

Tim Cooper 13 年前

当然。我们会向您指出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
}

顺便说一下,您在问题中使用simplecommand有点迂回。而不是这个:

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

你只需要:

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

指定lambda实际上只有在这样进行内联工作时才有用:

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