c# - 如何通过绑定(bind)到 ViewModel 来设置正确的 RadioButton.IsChecked 属性为真？

Question

我有以下场景，其中有这样一个类:

public class PetOwnerViewModel{
public PetOwnerStatus Status{get{return _petOwner.Status;}}

    public ICommand SetStatusCommand {get{...}}
}

DataContext 是一组类似这样的 RadioButtons:

<Parent DataContext="{Binding Path=PetOwner}" >
    <Parent.Resources>
        <myenums:PetOwnerStatus x:Key="CATLOVER">
            CatLover
        </myenums:PetOwnerStatus>
        <myenums:PetOwnerStatus x:Key="DOGLOVER">
            DogLover
        </myenums:PetOwnerStatus>
    </Parent.Resources>     
<StackPanel>
        <RadioButton Name="catLoverRadioButton"
                    Command="{Binding SetStatusCommand}"  
                CommandParameter="{StaticResource DOGLOVER}"
        GroupName="PetOwnerStatusRadioButtonGroup">
            Cat Lover
    </RadioButton>
        <RadioButton Name="dogLoverRadioButton"
                    Command="{Binding SetStatusCommand}"
                    CommandParameter="{StaticResource CATLOVER}"
        GroupName="SubjectStatusRadioButtonGroup" >
            Dog Lover
        </RadioButton>
    </StackPanel>
</Parent>

如何将 View 绑定(bind)到 ViewModel，以便在 PetOwnerViewModel.Status 返回 PetOwnerStatus.CatLover 时，catLoverRadioButton.IsChecked 为真。

Answer 1

您可以使用数据模板使这类事情变得非常动态，例如

(-- 编辑: 使用已经具有 SelectedItem 属性的 ListBox 更有意义，请参阅this revised answer --)

public partial class MainWindow : Window, INotifyPropertyChanged
{
    //For simplicity in put everything in the Window rather than models and view-models
    public enum TestEnum { Ichi, Ni, San }

    private TestEnum _EnumValue;
    public TestEnum EnumValue
    {
        get { return _EnumValue; }
        set
        {
            if (_EnumValue != value)
            {
                _EnumValue = value;
                PropertyChanged.Notify(() => this.EnumValue);
            }
        }
    }

    //...
}

<ItemsControl>
    <ItemsControl.Resources>
        <!-- Gets the enum values -->
        <ObjectDataProvider x:Key="items" MethodName="GetValues" ObjectType="{x:Type sys:Enum}">
            <ObjectDataProvider.MethodParameters>
                <x:Type TypeName="local:MainWindow+TestEnum" />
            </ObjectDataProvider.MethodParameters>
        </ObjectDataProvider>
        <!-- A MultiValueConverter which compares for equality -->
        <vc:EqualityComparisonConverter x:Key="eqc" />
    </ItemsControl.Resources>
    <ItemsControl.ItemsSource>
        <Binding Source="{StaticResource items}" />
    </ItemsControl.ItemsSource>
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <RadioButton Content="{Binding}" GroupName="TestEnumGroup"
                    Command="{x:Static local:Commands.DoStuff}" CommandParameter="{Binding}">
                <RadioButton.IsChecked>
                    <MultiBinding Converter="{StaticResource eqc}" Mode="OneWay">
                        <!-- This should point to the viewmodel enum property -->
                        <Binding ElementName="Window" Path="DataContext.EnumValue" />
                        <!-- This passes the DataContext, the enum value behind the templated item, to the converter -->
                        <Binding />
                    </MultiBinding>
                </RadioButton.IsChecked>
            </RadioButton>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

private void DoStuff_Executed(object sender, ExecutedRoutedEventArgs e)
{
    TestEnum enumval = (TestEnum)e.Parameter;
    EnumValue = enumval;
}

这对原始枚举值进行操作，您可以使用属性通过显示友好的字符串来扩充它们。

因为 IsChecked 绑定(bind)在所有 RadioButton 上，所以 RadioButton.GroupName 变得多余。

(我没有提供我对 EqualityComparisonConverter 的实现，因为它可能很糟糕，不过正确实现它应该不会太难)