这是一个展示我遇到问题的行为的示例。我有一个数据网格绑定到viewmodel中的可观察的记录集合。在DataGrid中,我有一个DataGridTemplateColumn,它包含一个从viewmodel中的列表填充的组合框。该数据网格还包含文本列。窗口底部有一些文本框来显示记录内容。DataGrid中的WPF组合框
<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,因此数据网格是空的,仅显示一个包含组合框线。如果用户首先将数据输入到文本列中,则将记录添加到该集合,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,那么当另一列被选中时,该值将消失。如果首先选择将组合框数据添加到记录中,如何获取?
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);
}
}
备案类:
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");
}
}
}
国家类:
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));
}
}
}
感谢您的帮助!
编辑感谢您的帮助马克,我跑,你在下面你的答案提供的代码,但我仍然不能在窗口底部得到的文本框中国家代码。我得到这些错误:
System.Windows.Data Error: 23 : Cannot convert '{NewItemPlaceholder}' from type 'NamedObject' to type 'CustomersFreezable.RecordViewModel' for 'en-US' culture with default conversions; consider using Converter property of Binding. NotSupportedException:'System.NotSupportedException: TypeConverter cannot convert from MS.Internal.NamedObject. at System.ComponentModel.TypeConverter.GetConvertFromException(Object value) at 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 Error: 7 : ConvertBack cannot convert value '{NewItemPlaceholder}' (type 'NamedObject'). BindingExpression:Path=SelectedRow; DataItem='GridModel' (HashCode=62992796); target element is 'DataGrid' (Name='dgCustomers'); target property is 'SelectedItem' (type 'Object') NotSupportedException:'System.NotSupportedException: TypeConverter cannot convert from MS.Internal.NamedObject. 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 culture) at System.Windows.Data.BindingExpression.ConvertBackHelper(IValueConverter converter, Object value, Type sourceType, Object parameter, CultureInfo culture)' Datagrid selection changed Datagrid selection changed
System.Windows.Data Error: 40 : BindingExpression path error: 'countryCode' property not found on 'object' ''RecordViewModel' (HashCode=47081572)'. BindingExpression:Path=SelectedItem.countryCode; DataItem='DataGrid' (Name='dgCustomers'); target element is 'TextBox' (Name='txtCode'); target property is 'Text' (type 'String')
System.Windows.Data Error: 23 : Cannot convert '{NewItemPlaceholder}' from type 'NamedObject' to type 'CustomersFreezable.RecordViewModel' for 'en-US' culture with default conversions; consider using Converter property of Binding. NotSupportedException:'System.NotSupportedException: TypeConverter cannot convert from MS.Internal.NamedObject. at System.ComponentModel.TypeConverter.GetConvertFromException(Object value) at 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 Error: 7 : ConvertBack cannot convert value '{NewItemPlaceholder}' (type 'NamedObject'). BindingExpression:Path=SelectedRow; DataItem='GridModel' (HashCode=62992796); target element is 'DataGrid' (Name='dgCustomers'); target property is 'SelectedItem' (type 'Object') NotSupportedException:'System.NotSupportedException: TypeConverter cannot convert from MS.Internal.NamedObject. 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 culture) at System.Windows.Data.BindingExpression.ConvertBackHelper(IValueConverter converter, Object value, Type sourceType, Object parameter, CultureInfo culture)' Datagrid selection changed
System.Windows.Data Error: 40 : BindingExpression path error: 'countryCode' property not found on 'object' ''RecordViewModel' (HashCode=47081572)'. BindingExpression:Path=SelectedItem.countryCode; DataItem='DataGrid' (Name='dgCustomers'); target element is 'TextBox' (Name='txtCode'); target property is 'Text' (type 'String')
我试图通过改变静态资源,解决BindingExpression路径错误:
<local:BindingProxy x:Key="CountryProxy" Data="{Binding}" />
,因此DataGrid的ItemsSource时:
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,但仍然没有看到文本框中的任何东西。你能告诉我什么是错的吗?
任何批评,当它是如此有建设性:)赞赏我运行您发送的代码,但仍然没有看到窗口底部的文本框中的countryCode。输出窗口中有几个错误;我编辑了这个问题来添加它们。 –
对不起,国家代码的绑定不正确,我在上面的XAML中修复了它。我注意到的另一件事是底部的那些字段直接绑定到元素。虽然这通常起作用,但如果绑定到视图模型字段(现在我已更改该代码执行),您会发现在问题的路上遇到的问题更少,特别是如果您开始移动XAML或者如果您需要在代码中添加断点以确保控件正常工作。 –
最后一件事......底部的国家/地区代码编辑字段目前正确显示国家/地区代码,但编辑它不会传播回记录,这基本上是在数据网格中使用组合框的一个副作用,但国家代码如下。如果你确实需要这个功能,那么你需要添加一个countryCode字段到视图模型。这引发了视图模型如何首先获得国家数组......这可以通过让GridModel监视将新的RecordViewModel添加到ObservableCollection并在创建它们时初始化它们来完成。 –