Question

我有一个与模型绑定的表单。有一个标准的基本模型和少数儿童模型（附加字段）。

在模型控件上方有一个单选按钮组，在选择其中一个时，会出现前面提到的附加字段（在本例中为句子字段）。

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private void sentencedPersonRadioButton_Checked(object sender, RoutedEventArgs e)
    {
        sentenceTextBox.Visibility = Visibility.Visible;
        DataContext = new SentencedPerson();
    }

    private void personRadioButton_Checked(object sender, RoutedEventArgs e)
    {
        sentenceTextBox.Visibility = Visibility.Hidden;
        DataContext = new Person();
    }
}

让我们说有一个人和SentencedPerson：

public class Person: INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChanged(String propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    private String name;
    public String Name
    {
        get
        {
            return name;
        }

        set
        {
            if (value == name)
            {
                return;
            }

            name = value;
            OnPropertyChanged("Name");
        }
    }
}

public class SentencedPerson : Person
{
    private String sentence;
    public String Sentence
    {
        get
        {
            return sentence;
        }

        set
        {
            if (value == sentence)
            {
                return;
            }

            sentence = value;
            OnPropertyChanged("Sentence");
        }
    }
}

设计此类连接的正确方法是什么？添加新的＆＃39;已检查＆＃39;事件处理程序感觉很麻烦...我听说过MVVM模式，里面会有Person和SentencedPerson道具的某种PersonContext。但它并没有改变“检查”的需要。事件

也知道存在问题，因为公共字段的值是在设置新的DataContext之后。

Answer 1

这是一个相当广泛的问题，但我会给你一些指示。

MVVM是推荐的设计模式，用于构建基于XAML的应用程序。

您可以使用＆＃34; CurrentSelectedContent＆＃34;创建一个视图模型类。类型为object或Person的属性以及将enum绑定到的RadioButton属性。

有关更多信息以及如何使用MVVM将RadioButton绑定到enum源属性的示例，请参阅以下链接：

How to bind RadioButtons to an enum?

完成此操作后，您可以设置＆＃34; CurrentSelectedContent＆＃34;的值。属性基于视图模型中enum源属性的setter中的单选按钮选择：

private MyLovelyEnum _enum;
public MyLovelyEnum VeryLovelyEnum
{
    get
    {
        return _enum;
    }
    set
    {
        _enum = value;
        switch (value)
        {
            case MyLovelyEnum.Person:
                CurrentSelectedContent = new Person();
                break;
            //...
        }
        OnPropertyChanged("VeryLovelyEnum");

    }
}

确保＆＃34; CurrentSelectedContent＆＃34; property引发PropertyChanged事件，视图模型类实现INotifyPropertyChanged接口。

在视图中，您可以使用ContentControl并将其Content属性绑定到＆＃34; CurrentSelectedContent＆＃34;属性：

    <ContentControl Content="{Binding Content}">
        <ContentControl.ContentTemplate>
            <DataTemplate>
                <TextBox Text="{Binding Name}" />
            </DataTemplate>
        </ContentControl.ContentTemplate>
    </ContentControl>

另外，请确保将视图的DataContext设置为视图模型的实例：

public MainWindow()
{
    InitializeComponent();
    DataContext = new ViewModel();
}

这是如何使用MVVM模式执行此操作的粗略思路。您不是在视图的代码隐藏中处理事件而是绑定到源属性，而不是显式设置特定UI元素的DataContext属性，而是将Content的{{1}}属性绑定到您在视图模型类中创建的对象。

希望有所帮助。

Answer 2

你只需要一个型号：

public class Person : INotifyPropertyChanged
{
    string _name;
    public string Name { get { return _name; } set { _name = value; RaisePropertyChanged("Name"); } }

    bool _isSentenced;
    public bool IsSentenced { get { return _isSentenced; } set { _isSentenced = value; RaisePropertyChanged("IsSentenced"); } }

    string _sentence;
    public string Sentence { get { return _sentence; } set { _sentence = value; RaisePropertyChanged("Sentence"); } }

    public event PropertyChangedEventHandler PropertyChanged;
    void RaisePropertyChanged(string propname)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propname));
    } 
}

使用IsSentenced并将RadioButton绑定到它。另外，使用Visibility to Bool转换器检查显示Sentence字符串的TextBox的可见性到RadioButton的IsChecked属性。这是一个简单的例子：

<Window.Resources>
    <local:VisibilityToBoolConverter x:Key="VisibilityToBoolConverter"/>
</Window.Resources>
<ListBox DataContext="{Binding}" ItemsSource="{Binding Persons}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <StackPanel>
                <TextBox Text="{Binding Name}" />
                <RadioButton Content="Is sentenced to death" IsChecked="{Binding IsSentenced}" />
                <DockPanel  Visibility="{Binding IsSentenced , Converter={StaticResource VisibilityToBoolConverter}}">
                    <Label Content="Sentence:  "/>
                    <TextBlock Text="{Binding Sentence}" />
                </DockPanel>
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate> 
</ListBox>

其中

public class VisibilityToBoolConverter : IValueConverter
{ 
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if ((bool)value == true)
            return Visibility.Visible;
        return Visibility.Collapsed;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if ((Visibility)value ==  Visibility.Visible)
            return true;
        return false;
    }
}

并且ViewModel是：

public class PersonViewModel : INotifyPropertyChanged
{
    public PersonViewModel()
    {
        Person m1 = new Person() { Name = "person 1", IsSentenced = false, Sentence = "S S S" };
        Person m2 = new Person() { Name = "person 2", IsSentenced = false, Sentence = "B B B" };
        Person m3 = new Person() { Name = "person 3", IsSentenced = true, Sentence = "F F F" };
        _persons = new ObservableCollection<Person>() { m1, m2, m3 }; 

    } 
    ObservableCollection<Person> _persons;
    public ObservableCollection<Person> Persons { get { return _persons; } set { _persons = value; RaisePropertyChanged("Persons"); } }

    public event PropertyChangedEventHandler PropertyChanged;
    void RaisePropertyChanged(string propname)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propname));
    }
}

你的主窗口应该设置DataContext：

    public MainWindow()
    { 
        PersonViewModel mv = new PersonViewModel();
        this.DataContext = mv;
        InitializeComponent(); 
    }

修改

如果一个人有很多状态，ComboBox是一个更自然的选择。你应该有一个描述状态的枚举：

public enum MyTypes { None, IsA, IsB, IsC }

并且Person应该有一个显示状态的peroperty：

public class Person : INotifyPropertyChanged { MyTypes _thetype; public MyTypes TheType { get { return _thetype; } set { _thetype = value; RaisePropertyChanged("TheType"); } } string _name; public string Name { get { return _name; } set { _name = value; RaisePropertyChanged("Name"); } } public event PropertyChangedEventHandler PropertyChanged; void RaisePropertyChanged(string propname) { PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propname)); } }

由于您需要将ComboBox的ItemsSource绑定到状态列表，因此可以调整ViewModel以获得这样的列表：

public class PersonViewModel : INotifyPropertyChanged { public PersonViewModel() { Person m0 = new Person() { Name = "person 1", TheType = MyTypes.None }; Person m1 = new Person() { Name = "person 1", TheType = MyTypes.IsA }; Person m2 = new Person() { Name = "person 2", TheType = MyTypes.IsB }; Person m3 = new Person() { Name = "person 3", TheType = MyTypes.IsC }; _persons = new ObservableCollection<Person>() { m0, m1, m2, m3 }; _types = Enum.GetNames(typeof(MyTypes)).ToList(); } List<string> _types; public List<string> Types { get { return _types; } } ObservableCollection<Person> _persons; public ObservableCollection<Person> Persons { get { return _persons; } set { _persons = value; RaisePropertyChanged("Persons"); } } public event PropertyChangedEventHandler PropertyChanged; void RaisePropertyChanged(string propname) { PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propname)); } }

最后，观点：

<Window.Resources> <local:EnumToSentenceConverterx:Key="EnumToSentenceConverter"/> <local:NoneToCollapsedConverter x:Key="NoneToCollapsedConverter"/> <local:EnumToStringConverter x:Key="EnumToStringConverter"/> </Window.Resources> <ListBox Name="lb" DataContext="{Binding}" ItemsSource="{Binding Persons}"> <ListBox.ItemTemplate> <DataTemplate> <StackPanel> <TextBox Text="{Binding Name}" /> <ComboBox Name="cb" ItemsSource="{Binding ElementName=lb, Path=DataContext.Types}" SelectedValue="{Binding TheType, Mode=TwoWay, Converter={StaticResource EnumToStringConverter}}" /> <DockPanel Visibility="{Binding ElementName=cb, Path=SelectedValue, Converter={StaticResource NoneToCollapsedConverter}}"> <Label Content="Sentence: " DockPanel.Dock="Left"/> <TextBlock Text="{Binding TheType, Converter={StaticResource EnumToStringConverter}}" DockPanel.Dock="Right" VerticalAlignment="Center" /> </DockPanel> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> </ListBox>

请注意，您需要三个转换器。一个将Sentence部分的Visibility设置为Collapsed，类型为None：

public class NoneToCollapsedConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { if (value.ToString() == "None") return Visibility.Collapsed; return Visibility.Visible; } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { throw new NotImplementedException(); } }

另外两个是自我描述性的：

public class EnumToStringConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { return value.ToString(); } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { return Enum.Parse(typeof(MyTypes), value.ToString()); } }

和

public class EnumToSentenceConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { switch ((MyTypes)value) { case MyTypes.IsA: break; } } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { throw new NotImplementedException(); } }

希望它有所帮助。

如何在将表单控件绑定到类层次结构时避免使用繁琐的代码？

2 个答案: