之前写过的一遍文章,在这里直接贴出来。
场景:根据配置文件显示DataGrid中的某些列。
问题:Columns集合只是DataGrid的一个属性,这个集合在逻辑树或视觉树中是看不到的,也不会继承DataContext属性。
通过网上查阅各种资料,方法可以归结以下几种,下面将一一展示。
方法一:对DataGridColumn附加DataContext属性
该方法需要用到一个帮助类(需要创建一个全局实例),具体内容如下:
public class DataGridContextHelper
{
static DataGridContextHelper()
{
DependencyProperty dp = FrameworkElement.DataContextProperty.AddOwner(typeof(DataGridColumn));
FrameworkElement.DataContextProperty.OverrideMetadata(typeof(DataGrid),
new FrameworkPropertyMetadata
(null, FrameworkPropertyMetadataOptions.Inherits,
new PropertyChangedCallback(OnDataContextChanged)));
}
public static void OnDataContextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
DataGrid grid = d as DataGrid;
if (grid != null)
{
foreach (DataGridColumn col in grid.Columns)
{
col.SetValue(FrameworkElement.DataContextProperty, e.NewValue);
}
}
}
}
前台绑定示例
<DataGridTextColumn x:Name="col2" Header="TestColumn" Visibility="{Binding (FrameworkElement.DataContext).Show,RelativeSource={RelativeSource Self},Converter={StaticResource cc}}">
</DataGridTextColumn>
后台绑定示例
var binding = new Binding();
binding.Mode = BindingMode.OneWay;
binding.RelativeSource=new RelativeSource(RelativeSourceMode.Self);
binding.Converter = new BooleanToVisibilityConverter();
binding.Path=new PropertyPath("(FrameworkElement.DataContext).Show");
BindingOperations.SetBinding(obj, DataGridColumn.VisibilityProperty, binding);
方法二:通过Source直接与Vm绑定
示例代码:
var binding = new Binding();
binding.Mode = BindingMode.OneWay;
binding.Source = vm;
binding.Converter = new BooleanToVisibilityConverter();
binding.Path = new PropertyPath("Show");
BindingOperations.SetBinding(obj, DataGridColumn.VisibilityProperty, binding);
方法三:通过Source与VM的一个代理类进行绑定
代理类
Freezable可以继承DataContext即使它们不在视觉树或逻辑树中
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); }
}
public static readonly DependencyProperty DataProperty =
DependencyProperty.Register("Data", typeof(object),
typeof(BindingProxy));
}
前台绑定代码
<DataGrid x:Name="dg" HorizontalAlignment="Left" VerticalAlignment="Top" Height="253" Width="436" ItemsSource="{Binding Persons}"
AutoGenerateColumns="False">
<DataGrid.Resources>
<dgTest:BindingProxy x:Key="proxy" Data="{Binding}"/>
</DataGrid.Resources>
<DataGrid.Columns>
<DataGridTextColumn x:Name="col1" Header="TestColumn" Binding="{Binding Name}"></DataGridTextColumn>
<DataGridTextColumn x:Name="col2" Header="TestColumn"
Visibility="{Binding (FrameworkElement.DataContext).Show,RelativeSource={RelativeSource Self},Converter={StaticResource cc}}"></DataGridTextColumn>
<DataGridTextColumn x:Name="col3" Header="TestColumn"
Visibility="{Binding Data.Show,Source={StaticResource proxy},Converter={StaticResource cc}}"></DataGridTextColumn>
</DataGrid.Columns>
</DataGrid>
方法四:通过一个代理控件来实现
代理控件与代理对象的解决方式类似,都是因为其可以继承DataContext属性,只是一个在逻辑树中看的到,一个看不到。示例如下:
<FrameworkElement x:Name="dummyElement" Visibility="Collapsed"/>
<DataGrid>
<DataGrid.Columns>
<DataGridTextColumn Header="Test"
Binding="{Binding Name}"
Visibility="{Binding DataContext.IsEnable,
Source={x:Reference dummyElement}}"/>
</DataGrid.Columns>
</DataGrid>