c# - C#/MVVM : Enable/Disable Buttons based on another control's property

Question

说我有一个选项卡控件，它显示各种类型的数据，例如EditorTabViewModel和PreviewTabViewModel都继承自TabViewModel。实现类似于tutorial on MSDN

我想根据 Activity 选项卡启用按钮，无论是EditorTabViewModel还是PreviewTabViewModel。我该如何实现？

更新

public ICommand EditorCommand
{
    get
    {
        if (_editorCommand == null) {
            _editorCommand = new RelayCommand(() =>
            {
                MessageBox.Show("Editor");
            }, () =>
            {
                var enabled = true;
                var viewSource = CollectionViewSource.GetDefaultView(Tabs);
                viewSource.CurrentChanged += (o, e) =>
                {
                    if (viewSource.CurrentItem is EditorTabViewModel)
                    {
                        enabled = false;
                    }
                };
                return enabled;
            });
        }
        return _editorCommand;
    }
}

更新2

public ICommand PreviewCommand
{
    get
    {
        if (_previewCommand == null) {
            _previewCommand = new RelayCommand(() =>
            {
                MessageBox.Show("Preview");
            }, () =>
            {
                var viewSource = CollectionViewSource.GetDefaultView(Tabs);
                var enabled = viewSource.CurrentItem is EditorTabViewModel;
                viewSource.CurrentChanged += (o, e) =>
                {
                    CommandManager.InvalidateRequerySuggested();
                };
                return enabled;
            });
        }
        return _previewCommand;
    }
}

Answer 1

我建议您创建一个ICommand实现，该实现在包含2个选项卡控件的ICollectionView上构造。然后，该命令可以对集合 View 中的CurrentChanged事件使用react，以确定是否应启用它，并引发CanExecuteChanged事件以指示更改。

class MyCommand : ICommand
{
    private bool _isEnabled = true;

    public MyCommand(MyTopLevelViewModel viewModel)
    {
        var viewSource = CollectionViewSource.GetDefaultView(viewModel.Tabs);
        viewSource.CurrentChanged += (o,e) =>
            {
                _isEnabled = (viewSource.CurrentItem is EditorTabViewModel); //or however you want to decide

                if (this.CanExecuteChanged != null) 
                     this.CanExecuteChanged(this, EventArgs.Empty);

            };
    }

    public void Execute(object parameter) { /*...*/ }

    public bool CanExecute(object parameter) { return _isEnabled; }

    public event EventHandler CanExecuteChanged;
}

注意:您将需要在标签控件上设置 IsSyncronizedWithCurrentItem属性:

<TabControl IsSynchronizedWithCurrentItem="True" />