如何在 wpf 的窗口中设置多个 Datacontext

Question

在应用程序中，我想绑定来自 2 个不同视图模型的数据。我必须将 datacontext 设置为两个不同的视图模型。

当我使用两个不同的视图模型时，只有最后一组数据上下文优先。

因此，我有一个带有其他视图模型类的 CombinedDataContext 类。

我可以更新到视图模型，但它没有显示在视图上。

ViewModel1

public class Data1 : INotifyPropertyChanged
    {
        private string _string1;

        public string String1
        {
            get { return _string1; }
            set { _string1 = value; onPropertyChnaged("String1"); }
        }

        private void onPropertyChnaged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

    }

ViewModel2

public class Data2 : INotifyPropertyChanged
    {
        private string _string2;

        public string String2
        {
            get { return _string2; }
            set { _string2 = value; onPropertyChnaged("String2");}
        }

        private void onPropertyChnaged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

    }

观看次数：

public partial class MainWindow : Window
    {
        Data12 d12 = new Data12 { };
        public MainWindow()
        {
            InitializeComponent();
            DataContext = d12;
        }

        private void button_Click(object sender, RoutedEventArgs e)
        {
            ViewModel_1();
            ViewModel_2();
        }

        private void ViewModel_1()
        {
            var viewmodel = DataContext as Data12;
            viewmodel.Data1.String1 = textBox.Text;
        }
        private void ViewModel_2()
        {
            var viewmodel = DataContext as Data12;
            viewmodel.Data1.String1 = textBox.Text;
        }
}

组合视图模型：

class Data12
    {
        public Data1 Data1 = new Data1();
        public Data2 Data2= new Data2();
    }

Xaml 文件：

<Grid>

        <Label x:Name="label" HorizontalAlignment="Left" Margin="92,61,0,0" VerticalAlignment="Top" Content="{Binding Data1.String1}"  />

        <Label x:Name="label1" Content="{Binding Data2.String2}" HorizontalAlignment="Left" Margin="349,61,0,0" VerticalAlignment="Top" />
        <TextBox x:Name="textBox" HorizontalAlignment="Left" Height="23" Margin="65,153,0,0" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top" Width="120"/>
        <TextBox x:Name="textBox1" HorizontalAlignment="Left" Height="23" Margin="360,153,0,0" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top" Width="120"/>
        <Button x:Name="button" Content="Button" HorizontalAlignment="Left" Margin="205,246,0,0" VerticalAlignment="Top" Width="75" Click="button_Click" />
</Grid>

没有 Nullreference，但绑定不起作用。我什至尝试通过实例化内部属性，但没有奏效。请帮助我。

Answer 1

你不能绑定字段，所以只要把它们变成属性就可以了：

class Data12
{
    public Data12()
    {
        this.Data1 = new Data1();
        this.Data2 = new Data2();
    }
    public Data1 Data1 { get; private set; }
    public Data2 Data2 { get; private set; }
}

正如@Clemens 所说，这可以缩短为

class Data12
{
    public Data1 Data1 { get; } = new Data1();
    public Data2 Data2 { get; } = new Data2();
}