绑定到WinForms中的命令

Question

如何在视图模型中将按钮绑定到命令,就像使用MVVM的WPF一样？

Answer 1

我想知道是否可以完成相同的事情并结束编写一个简单的CommandManager来查询已注册的命令(在Application.Idle事件上)并使用数据绑定来更改控件的Enabled状态

这是我现在使用的代码:

public class CommandManager: Component
{
    private IList<ICommand> Commands { get; set; }
    private IList<ICommandBinder> Binders { get; set; }

    public CommandManager()
    {
        Commands = new List<ICommand>();

        Binders = new List<ICommandBinder>
                      {
                          new ControlBinder(),
                          new MenuItemCommandBinder()
                      };

        Application.Idle += UpdateCommandState;
    }

    private void UpdateCommandState(object sender, EventArgs e)
    {
        Commands.Do(c => c.Enabled);
    }

    public CommandManager Bind(ICommand command, IComponent component)
    {
        if (!Commands.Contains(command))
            Commands.Add(command);

        FindBinder(component).Bind(command, component);
        return this;
    }

    protected ICommandBinder FindBinder(IComponent component)
    {
        var binder = GetBinderFor(component);

        if (binder == null)
            throw new Exception(string.Format("No binding found for component of type {0}", component.GetType().Name));

        return binder;
    }

    private ICommandBinder GetBinderFor(IComponent component)
    {
        var type = component.GetType();
        while (type != null)
        {
            var binder = Binders.FirstOrDefault(x => x.SourceType == type);
            if (binder != null)
                return binder;

            type = type.BaseType;
        }

        return null;
    }

    protected override void Dispose(bool disposing)
    {
        if (disposing)
            Application.Idle -= UpdateCommandState;

        base.Dispose(disposing);
    }
}

public static class Extensions
{
    public static void Do<T>(this IEnumerable<T> @this, Func<T, object> lambda)
    {
        foreach (var item in @this)
            lambda(item);
    }
}
public abstract class CommandBinder<T> : ICommandBinder where T: IComponent
{
    public Type SourceType
    {
        get { return typeof (T); }
    }

    public void Bind(ICommand command, object source)
    {
        Bind(command, (T) source); 
    }

    protected abstract void Bind(ICommand command, T source);
}

public class ControlBinder: CommandBinder<Control>
{
    protected override void Bind(ICommand command, Control source)
    {
        source.DataBindings.Add("Enabled", command, "Enabled");
        source.DataBindings.Add("Text", command, "Name");
        source.Click += (o, e) => command.Execute();
    }
}

public class MenuItemCommandBinder : CommandBinder<ToolStripItem>
{
    protected override void Bind(ICommand command, ToolStripItem source)
    {
        source.Text = command.Name;
        source.Enabled = command.Enabled;
        source.Click += (o, e) => command.Execute();

        command.PropertyChanged += (o, e) => source.Enabled = command.Enabled;
    }
}

这是如何使用它的例子:

public partial class Form1 : Form
{
    private CommandManager commandManager;

    public ICommand CommandA { get; set; }
    public ICommand CommandB { get; set; }

    public bool condition;

    public Form1()
    {
        InitializeComponent();

        commandManager = new CommandManager();

        CommandA = new DelegateCommand("Command 1", OnTrue, OnExecute);
        CommandB = new DelegateCommand("Command 2", OnFalse, OnExecute);

        commandManager.Bind(CommandA, button1);
        commandManager.Bind(CommandB, button2);

        commandManager.Bind(CommandA, command1ToolStripMenuItem);
        commandManager.Bind(CommandB, command2ToolStripMenuItem);
    }

    private bool OnFalse()
    {
        return !condition;
    }

    private bool OnTrue()
    {
        return condition;
    }

    private void OnExecute()
    {
        condition = !condition;
    }
}

此外,如果您需要代码,我在这里写博客

Answer 2

您可以创建一个通用命令绑定类,该类允许将命令绑定到任何继承的类ButtonBase.

public class CommandBinding<T> where T : ButtonBase
{
    private T _invoker;
    private ICommand _command;

    public CommandBinding(T invoker, ICommand command)
    {
        _invoker = invoker;
        _command = command;

        _invoker.Enabled = _command.CanExecute(null);
        _invoker.Click += delegate { _command.Execute(null); };
        _command.CanExecuteChanged += delegate { _invoker.Enabled = _command.CanExecute(null); };
    }
}

然后可以使用以下代码设置命令绑定:

CommandBinding<Button> cmdBinding = 
    new CommandBinding<Button>(btnCut, CutCommand);

这只是我实现的基础,为您提供一个开始,所以自然会有一些注意事项:

• 该示例假定使用WPF ICommand接口,因此如果您拥有自己的命令模式实现,则可能必须更改.
• 应检查传入的参数是否为空引用.
• 更具体的实现应该有一些删除事件处理程序的方法,以避免内存泄漏.

通用约束也可以更改为Control暴露Click事件和Enabled属性,这意味着命令几乎可以绑定到任何Control.

Answer 3

我之前已将ICommand对象附加到和对象Tag的属性上。ButtonMenuItem

然后，我只是看看是否可以投射并运行它（如果可以的话），例如：

private void button1_Click(object sender, EventArgs e)
{
    ICommand command = ((Control)(sender)).Tag as ICommand;

    if (command != null)
    {
        command.Execute();
    }
}

为了更轻松的生活，请尝试对控件进行子类化（例如Button, MenuItem）