我有一个MVVM WPF应用程序。
我在WPF datagrid中有一个DataGridTextColumn。我想将其width属性绑定到转换器,并将其单元格值传递给它。对于此列,有时此列的所有单元格都为空,因此我还想将列宽设置为固定值,如果所有单元格都为空,则设置为20(与其最小宽度相同),否则设置为50。问题是没有调用转换器。
为了简化和关注有趣的部分,我只在这里发布了相关代码:
<DataGrid Grid.Row="1"
AutoGenerateColumns="False"
ItemsSource="{Binding Path=MyListOfItems}"
VerticalAlignment="Stretch" IsReadOnly="True"
SelectionMode="Single" ColumnWidth="*"
>
<DataGridTextColumn
CellStyle="{StaticResource MyDataGridCellStyle}"
Binding="{Binding Path=EntryDate, StringFormat=\{0:dd/MM/yyyy\}}"
Header="Entry Date"
Width="{Binding Path=EntryDate, Converter={StaticResource ColumnWidthConverter}}"
HeaderStyle="{DynamicResource CenterGridHeaderStyle}">
</DataGridTextColumn>
</DataGrid>
转换器
:
public class ColumnWidthConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
string cellContent= (string)value;
return (string.IsNullOrEmpty(cellContent.Trim()) ? 20 : 50);
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
我的最终目标是在所有单元格都为空时将列宽设置为20,否则将列宽设置为50。我认为使用转换器是个好主意,但从未调用过转换器。为什么?
使现代化
:
最后,我做了@Andy建议的事情:将视图模型中的属性绑定到视图中的datagridtextcolumn width属性。视图模型上的此属性迭代所有列单元格,然后相应地设置宽度。见下文。我的问题是,视图模型上的这个属性“EntryDateColumnWidth”只在应用程序启动时第一次激发,然后在调用OnPropertyChanged(“EntryDateColumnWidth”)时才激发。
查看模型
:
public class MyMainViewModel : ViewModelBase
{
public DataGridLength EntryDateColumnWidth
{
get
{
bool isEmpty = this.MyListOfItems.TrueForAll(i => string.IsNullOrEmpty(i.EntryDate.ToString().Trim()));
return (isEmpty ? 20 : new DataGridLength(0, DataGridLengthUnitType.Auto));
}
}
}
此外,在视图模型中,当我为datagrid设置了项目列表时,我会执行:
OnPropertyChanged("EntryDateColumnWidth");
此属性返回DataGridLength对象,因为当任何列单元格不为空时,我需要将width设置为auto。
笔记
:ViewModelBase是实现INotifyPropertyChanged的抽象类。
看法
:
<DataGrid Grid.Row="1"
AutoGenerateColumns="False"
ItemsSource="{Binding Path=MyListOfItems}"
VerticalAlignment="Stretch" IsReadOnly="True"
SelectionMode="Single" ColumnWidth="*">
<DataGrid.Resources>
<local:BindingProxy x:Key="proxy" Data="{Binding}" />
</DataGrid.Resources>
<DataGridTextColumn
CellStyle="{StaticResource MyDataGridCellStyle}"
Binding="{Binding Path=EntryDate, StringFormat=\{0:dd/MM/yyyy\}}"
Header="Entry Date"
Width="{Binding Data.EntryDateColumnWidth, Source={StaticResource proxy}}"
HeaderStyle="{DynamicResource CenterGridHeaderStyle}">
</DataGridTextColumn>
</DataGrid>
类BindingProxy
:
namespace MyApp.Classes
{
public class BindingProxy : Freezable
{
#region Overrides of Freezable
protected override Freezable CreateInstanceCore()
{
return new BindingProxy();
}
#endregion
public object Data
{
get { return (object)GetValue(DataProperty); }
set { SetValue(DataProperty, value); }
}
// Using a DependencyProperty as the backing store for Data. This enables animation, styling, binding, etc...
public static readonly DependencyProperty DataProperty =
DependencyProperty.Register("Data", typeof(object), typeof(BindingProxy), new UIPropertyMetadata(null));
}
}
更新2
:
依赖关系对象类
:
namespace My.WPF.App.Classes
{
public class BridgeDO: DependencyObject
{
public DataGridLength DataComandaColWidth
{
get { return (DataGridLength)GetValue(DataComandaColWidthProperty); }
set { SetValue(DataComandaColWidthProperty, value); }
}
public static readonly DependencyProperty EntryDateColWidthProperty =
DependencyProperty.Register("EntryDateColWidth",
typeof(DataGridLength),
typeof(BridgeDO),
new PropertyMetadata(new DataGridLength(1, DataGridLengthUnitType.Auto)));
}
}
资源字典中的实例(DictionaryDO.xaml)
:
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:My.WPF.App.Classes">
<local:BridgeDO x:Key="DO"/>
</ResourceDictionary>
将其合并到资源字典(app.xaml)
:
<Application x:Class="My.WPF.Apps.MyApp.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:my="http://schemas.microsoft.com/wpf/2008/toolkit"
xmlns:local="clr-namespace:My.WPF.Apps.MyApp"
StartupUri="Main.xaml">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="Dictionaries/DictionaryDO.xaml"/>
</ResourceDictionary.MergedDictionaries>
<!-- Styles -->
</ResourceDictionary>
</Application.Resources>
</Application>
窗
:
<Window x:Name="MainWindow" x:Class="My.WPF.Apps.MyApp.wMain"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Window.Resources>
<!-- Resources -->
</Window.Resources>
<DataGrid Grid.Row="1"
AutoGenerateColumns="False"
ItemsSource="{Binding Path=MyListOfItems}"
VerticalAlignment="Stretch" IsReadOnly="True"
SelectionMode="Single" ColumnWidth="*">
<DataGrid.Resources>
<local:BindingProxy x:Key="proxy" Data="{Binding}" />
</DataGrid.Resources>
<DataGridTextColumn
CellStyle="{StaticResource MyDataGridCellStyle}"
Binding="{Binding Path=EntryDate, StringFormat=\{0:dd/MM/yyyy\}}"
Header="Entry Date"
Width="{Binding EntryDateColWidth, Source={StaticResource DO}}"
HeaderStyle="{DynamicResource CenterGridHeaderStyle}">
</DataGridTextColumn>
</DataGrid>
</Window>
查看模型
:
public class myMainViewModel : ViewModelBase
{
private BridgeDO _do;
public myMainViewModel(IView view)
{
_view = view;
_do = Application.Current.Resources["DO"] as BridgeDO;
}
private void BackgroundWorker_DoWork()
{
// Do some stuff
SetColumnWidth();
}
private void SetColumnWidth()
{
_view.GetWindow().Dispatcher.Invoke(new Action(delegate
{
bool isEmpty = this.MyListOfItems.TrueForAll(e => !e.EntryDate.HasValue);
_do.SetValue(BridgeDO.EntryDateColWidthProperty, isEmpty ? new DataGridLength(22.0) : new DataGridLength(1, DataGridLengthUnitType.Auto));
}), DispatcherPriority.Render);
}
}
但列宽未更新。。。
