【发布时间】：2015-12-31 18:42:40
【问题描述】：
这是一个展示我遇到问题的行为的示例。我有一个数据网格，它绑定到视图模型中的可观察记录集合。在数据网格中，我有一个 DataGridTemplateColumn 包含一个组合框，该组合框是从视图模型中的列表中填充的。数据网格还包含文本列。窗口底部有一些文本框用于显示记录内容。
<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" SelectionChanged="dgCustomers_SelectionChanged">
<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，所以数据网格是空的，只显示一行包含组合框。如果用户首先在文本列中输入数据，则将一条记录添加到集合中，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ComboBox值，则选择另一列时，该值会消失。如果先选中，如何获取添加到记录中的组合框数据？
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;
}
}
网格模型：
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));
}
}
}
【问题讨论】：
标签： c# wpf mvvm combobox datagrid