在打开上下文菜单时提高上下文菜单命令的CanExcute [英] Raise context menu command's CanExcute while open the context menu

问题描述

在执行上下文菜单时可以执行ICommand打开

继续上面的查询，仍然无法实现。

With the continuation of the above query, Still its not able to achieve.

在打开上下文菜单时，是否有任何方法可以调用上下文菜单命令的CanExcute。

Is there any way to raise context menu command's CanExcute while open the context menu. This need to be done in the context menu itself and here am not able to access the viewmodel.

对此有任何想法吗？

    public static BaseCommand SaveCommand
    {
        get
        {
            if (saveCommand == null)
                saveCommand = new BaseCommand(OnSaveCommandClicked, OnSaveCommandCanExcute);

            return saveCommand;
        }
    }

其中BaseCommand派生自ICommand。

where BaseCommand is derived from ICommand.

public class BaseCommand : ICommand
{
    private Predicate<object> _canExecute;
    private Action<object> _method;
    public event EventHandler CanExecuteChanged;

    public BaseCommand(Action<object> method)
        : this(method, null)
    {
    }

    public BaseCommand(Action<object> method, Predicate<object> canExecute)
    {
        _method = method;
        _canExecute = canExecute;
    }

    public bool CanExecute(object parameter)
    {
        if (_canExecute == null)
        {
            return true;
        }

        return _canExecute(parameter);
    }

    public void Execute(object parameter)
    {
        _method.Invoke(parameter);
    }

}

推荐答案

在 BaseCommand 中，将 CanExecuteChanged 替换为以下内容。

Inside BaseCommand, replace the CanExecuteChanged to look like the following. And it will work the way you want it.

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

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