将选中的菜单项绑定到ViewModel命令

Question

我在XAML 3中定义了菜单项(使用WPF-MDI):

<MenuItem Header="_Generic" Name="Generic" ToolTip="Generic Visual Studio designer theme" 
          Command="{Binding Path=SelectGenericTheme}"/>
<MenuItem Header="_Luna" Name="Luna" ToolTip="Blue Windows XP theme"
          Command="{Binding Path=SelectLunaTheme}"/>
<MenuItem Header="_Aero" Name="Aero" ToolTip="Windows Vista/7 theme" 
          Command="{Binding Path=SelectAeroTheme}"/>

以及ViewModel中命令和当前选择的定义:

    public enum ESelectedTheme
    {
        Generic,
        Luna,
        Aero
    }

    ESelectedTheme _selectedTheme;

    ICommand _selectGenericThemeCommand;
    public ICommand SelectGenericThemeCommand
    {
        get { return _selectGenericThemeCommand ?? (_selectGenericThemeCommand = new RelayCommand(param => SelectGenericTheme(), 
            param => true)); }
    }

    void SelectGenericTheme()
    {
        _selectedTheme = ESelectedTheme.Generic;
    }


    ICommand _selectLunaThemeCommand;
    public ICommand SelectLunaThemeCommand
    {
        get
        {
            return _selectLunaThemeCommand ?? (_selectLunaThemeCommand = new RelayCommand(param => SelectLunaTheme(),
                param => true));
        }
    }

    void SelectLunaTheme()
    {
        _selectedTheme = ESelectedTheme.Luna;
    }


    ICommand _selectAeroThemeCommand;
    public ICommand SelectAeroThemeCommand
    {
        get
        {
            return _selectAeroThemeCommand ?? (_selectAeroThemeCommand = new RelayCommand(param => SelectAeroTheme(),
                param => true));
        }
    }

    void SelectAeroTheme()
    {
        _selectedTheme = ESelectedTheme.Aero;
    }

我有2个问题(希望在一个帖子中允许):

1. 我想将XAML中的IsChecked属性绑定到所选的值(_selectedTheme).我想我需要写一个转换器,但我不知道如何.
2. 我制作了3份ICommands(每个主题一个)...如果我有20个主题怎么办...有没有办法让这个代码参数化？

提前致谢.

Answer 1

没有必要参数化命令,因为绑定将执行所有操作,但如上所述,可以使用CommandParameter.这里转换器将获得enum参数.

一个例子:

<MenuItem Header="_Description" IsCheckable="True"
        IsChecked="{Binding Path=DisplayMode_Current,
                            Converter={StaticResource EnumToBooleanConv},
                            ConverterParameter=Description}" />
<MenuItem Header="_Web-Page" IsCheckable="True"
        IsChecked="{Binding Path=DisplayMode_Current,
                            Converter={StaticResource EnumToBooleanConv},
                            ConverterParameter=WebPage}" />

转换器看起来像这样:

public class EnumToBooleanConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        // You could also directly pass an enum value using {x:Static},
        // then there is no need to parse
        string parameterString = parameter as string;
        if (parameterString == null)
            return DependencyProperty.UnsetValue;

        if (Enum.IsDefined(value.GetType(), value) == false)
            return DependencyProperty.UnsetValue;

        object parameterValue = Enum.Parse(value.GetType(), parameterString);

        return parameterValue.Equals(value);
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        string parameterString = parameter as string;
        if (parameterString == null)
            return DependencyProperty.UnsetValue;

        return Enum.Parse(targetType, parameterString);
    }
}

由于XAML仍然冗长(并且多余!),您可以通过ItemsSource将父级绑定MenuItem到枚举值来进一步使用它,然后使用ItemTemplate和ItemContainerStyle.