DataGrid中的WPF组合框

这是一个展示我遇到麻烦的行为的例子 . 我有一个datagrid绑定到viewmodel中的可观察记录集合 . 在datagrid中，我有一个DataGridTemplateColumn，它包含一个组合框，该组合框是从viewmodel中的列表中填充的 . 数据网格还包含文本列 . 窗口底部有一些文本框可显示记录内容 .

<Window x:Class="Customer.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:Customer"
    Title="MainWindow" Height="350" Width="525">

    <Window.Resources>
        <local:SelectedRowConverter x:Key="selectedRowConverter"/>
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="8*"/>
            <RowDefinition Height="3*"/>
        </Grid.RowDefinitions>
        <DataGrid x:Name="dgCustomers" AutoGenerateColumns="False"
                  ItemsSource="{Binding customers}" SelectedItem="{Binding SelectedRow,
                    Converter={StaticResource selectedRowConverter}, Mode=TwoWay}"
                  CanUserAddRows="True" Grid.Row="0" >
            <DataGrid.Columns>
                <DataGridTemplateColumn Width="Auto" Header="Country">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <ComboBox x:Name="cmbCountry" ItemsSource="{Binding DataContext.countries,
                                RelativeSource={RelativeSource AncestorType={x:Type Window}}}"
                                      DisplayMemberPath="name" SelectedValuePath="name" Margin="5"
                                      SelectedItem="{Binding DataContext.SelectedCountry,
                                RelativeSource={RelativeSource AncestorType={x:Type Window}}, Mode=TwoWay,
                                UpdateSourceTrigger=PropertyChanged}" SelectionChanged="cmbCountry_SelectionChanged" />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
                <DataGridTextColumn Header="Name" Binding="{Binding name}" Width="1*"/>
                <DataGridTextColumn Header="Phone" Binding="{Binding phone}" Width="1*"/>
            </DataGrid.Columns>
        </DataGrid>

        <Grid x:Name="grdDisplay" DataContext="{Binding ElementName=dgCustomers}" Grid.Row="1">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="1*"/>
                <ColumnDefinition Width="1*"/>
                <ColumnDefinition Width="1*"/>
            </Grid.ColumnDefinitions>
            <Label Grid.Column="2" Content="Country:" VerticalAlignment="Center" HorizontalAlignment="Right"/>
            <Label Grid.Column="4" Content="Code:" VerticalAlignment="Center" HorizontalAlignment="Right"/>
            <BulletDecorator  Grid.Column="0">
                <BulletDecorator.Bullet>
                    <Label Content="Name:" VerticalAlignment="Center" HorizontalAlignment="Right"/>
                </BulletDecorator.Bullet>
                <TextBox x:Name="txtId" Text="{Binding ElementName=dgCustomers, Path=SelectedItem.name}" Margin="5,5,5,5"/>
            </BulletDecorator>
            <BulletDecorator Grid.Column="1">
                <BulletDecorator.Bullet>
                    <Label Content="Code:" VerticalAlignment="Center" HorizontalAlignment="Right"/>
                </BulletDecorator.Bullet>
                <TextBox x:Name="txtCode" Text="{Binding ElementName=dgCustomers, Path=SelectedItem.countryCode}" Margin="5,5,5,5"/>
            </BulletDecorator>
            <BulletDecorator Grid.Column="2">
                <BulletDecorator.Bullet>
                    <Label  Content="Phone:" VerticalAlignment="Center" HorizontalAlignment="Right"/>
                </BulletDecorator.Bullet>
                <TextBox x:Name="txtPhone" Text="{Binding ElementName=dgCustomers, Path=SelectedItem.phone}" Margin="5,5,5,5"/>
            </BulletDecorator>
        </Grid>
    </Grid>
</Window>

最初没有记录，因此datagrid为空，只显示包含组合框的一行 . 如果用户首先将数据输入到文本列中，则将记录添加到集合中，并且可以将组合框值添加到记录中 . 但是，如果用户首先选择组合框值，则在选择另一列时该值将消失 . 如果首先选择组合框数据，如何将其添加到记录中？

代码隐藏：

public partial class MainWindow : Window
{
    public GridModel gridModel { get; set; }

    public MainWindow()
    {
        InitializeComponent();
        gridModel = new GridModel();
        //dgCustomers.DataContext = gridModel;
        this.DataContext = gridModel;
    }

    private void cmbCountry_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        ComboBox c = sender as ComboBox;
        Debug.Print("ComboBox selection changed, index is " + c.SelectedIndex + ", selected item is " + c.SelectedItem);
    }
}

记录类：

public class Record : ViewModelBase
{
    private string _name;
    public string name
    {
        get { return _name; }
        set
        {
            _name = value;
            OnPropertyChanged("name");
        }
    }

    private string _phone;
    public string phone
    {
        get { return _phone; }
        set
        {
            _phone = value;
            OnPropertyChanged("phone");
        }
    }

    private int _countryCode;
    public int countryCode
    {
        get { return _countryCode; }
        set
        {
            _countryCode = value;
            OnPropertyChanged("countryCode");
        }
    }
}

国家级：

public class Country : ViewModelBase
{
    private string _name;
    public string name
    {
        get { return _name; }
        set
        {
            _name = value;
            OnPropertyChanged("name");
        }
    }

    private int _id;
    public int id
    {
        get { return _id; }
        set
        {
            _id = value;
            OnPropertyChanged("id");
        }
    }

    private int _code;
    public int code
    {
        get { return _code; }
        set
        {
            _code = value;
            OnPropertyChanged("code");
        }
    }

    public override string ToString()
    {
        return _name;
    }
}

GridModel：

public class GridModel : ViewModelBase
{
    public ObservableCollection<Record> customers { get; set; }
    public List<Country> countries { get; set; }
    public GridModel()
    {
        customers = new ObservableCollection<Record>();
        countries = new List<Country> { new Country { id = 1, name = "England", code = 44 }, new Country { id = 2, name = "Germany", code = 49 },
        new Country { id = 3, name = "US", code = 1}, new Country { id = 4, name = "Canada", code = 11 }};
    }

    private Country _selectedCountry;
    public Country SelectedCountry
    {
        get
        {
            return _selectedCountry;
        }
        set
        {
            _selectedCountry = value;
            _selectedRow.countryCode = _selectedCountry.code;
            OnPropertyChanged("SelectedRow");
        }
    }

    private Record _selectedRow;
    public Record SelectedRow
    {
        get
        {
            return _selectedRow;
        }
        set
        {
            _selectedRow = value;
            Debug.Print("Datagrid selection changed"); 
            OnPropertyChanged("SelectedRow");
        }
    }
}

转换器：

class Converters
{
}

public class SelectedRowConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value is Record)
            return value;
        return new Customer.Record();
    }
}

ViewModelBase：

public class ViewModelBase : INotifyPropertyChanged
{
    public ViewModelBase()
    {

    }

    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChanged(string name)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(name));
        }
    }
}

谢谢你的帮助！

EDIT 感谢帮助Mark，我'm running the code you provided in your answer below, but I'仍然没有在窗口底部的文本框中获取国家/地区代码 . 我收到这些错误：

System.Windows.Data错误：23：无法将''从'NamedObject'类型转换为'en-US'文化的'CustomersFreezable.RecordViewModel'，默认转换为;考虑使用Binding的Converter属性 . NotSupportedException：'System.NotSupportedException：TypeConverter无法从MS.Internal.NamedObject转换 . 在System.ComponentModel.TypeConverter.GetConvertFromException（Object value）处于System.ComponentModel.TypeConverter.ConvertFrom（ITypeDescriptorContext context，CultureInfo culture，Object value）at MS.Internal.Data.DefaultValueConverter.ConvertHelper（Object o，Type destinationType，DependencyObject targetElement， CultureInfo culture，Boolean isForward）'System.Windows.Data错误：7：ConvertBack无法转换值''（类型'NamedObject'） . BindingExpression：路径= SelectedRow; DataItem ='GridModel'（HashCode = 62992796）; target元素是'DataGrid'（Name ='dgCustomers'）; target属性为'SelectedItem'（类型'Object'）NotSupportedException：'System.NotSupportedException：TypeConverter无法从MS.Internal.NamedObject转换 . 在MS.Internal.Data.DefaultValueConverter.ConvertHelper（Object o，Type destinationType，DependencyObject targetElement，CultureInfo culture，Boolean isForward）at MS.Internal.Data.ObjectTargetConverter.ConvertBack（Object o，Type type，Object parameter，CultureInfo culture）at at 'System.Windows.Data.BindingExpression.ConvertBackHelper（IValueConverter converter，Object value，Type sourceType，Object parameter，CultureInfo culture）'Datagrid选择已更改Datagrid选择已更改System.Windows.Data错误：40：BindingExpression路径错误：'countryCode'属性不找到'object'''RecordViewModel'（HashCode = 47081572）' . BindingExpression：路径= SelectedItem.countryCode; DataItem ='DataGrid'（Name ='dgCustomers'）; target元素是'TextBox'（Name ='txtCode'）;目标属性是'Text'（类型'String'）System.Windows.Data错误：23：无法将''从类型'NamedObject'转换为'CustomersFreezable.RecordViewModel'，为'en-US'文化输入默认转换;考虑使用Binding的Converter属性 . NotSupportedException：'System.NotSupportedException：TypeConverter无法从MS.Internal.NamedObject转换 . 在System.ComponentModel.TypeConverter.GetConvertFromException（Object value）处于System.ComponentModel.TypeConverter.ConvertFrom（ITypeDescriptorContext context，CultureInfo culture，Object value）at MS.Internal.Data.DefaultValueConverter.ConvertHelper（Object o，Type destinationType，DependencyObject targetElement， CultureInfo culture，Boolean isForward）'System.Windows.Data错误：7：ConvertBack无法转换值''（类型'NamedObject'） . BindingExpression：路径= SelectedRow; DataItem ='GridModel'（HashCode = 62992796）; target元素是'DataGrid'（Name ='dgCustomers'）; target属性为'SelectedItem'（类型'Object'）NotSupportedException：'System.NotSupportedException：TypeConverter无法从MS.Internal.NamedObject转换 . at MS.Internal.Data.DefaultValueConverter.ConvertHelper（Object o，Type destinationType，DependencyObject targetElement，CultureInfo culture，Boolean isForward）at MS.Internal.Data.ObjectTargetConverter.ConvertBack（Object o，Type type，Object parameter，CultureInfo）System.Windows.Data.BindingExpression.ConvertBackHelper（IValueConverter转换器，Object值，Type sourceType，Object参数，CultureInfo文化）'Datagrid选择已更改System.Windows.Data错误：40：BindingExpression路径错误：'countryCode'属性不在找到'object'''RecordViewModel'（HashCode = 47081572）' . BindingExpression：路径= SelectedItem.countryCode; DataItem ='DataGrid'（Name ='dgCustomers'）; target元素是'TextBox'（Name ='txtCode'）; target属性是'Text'（类型'String'）

我试图通过更改静态资源来解决BindingExpression路径错误：

<local:BindingProxy x:Key="CountryProxy" Data="{Binding}" />

因此DataGrid的ItemsSource：

ItemsSource="{Binding Source={StaticResource ResourceKey=CountryProxy}, Path=Data.countries}" DisplayMemberPath="name"

和文本框的绑定：

<TextBox x:Name="txtCode" Text="{Binding Path=record.countryCode}" Margin="5,5,5,5"/>

这摆脱了错误40，但我仍然没有看到文本框中的任何内容 . 你能告诉我什么是错的吗？