これはそれほど難しいことではありません。質問があった2009年はどれほど難しかったかはわかりませんが、当時はそうでした。
このソリューションを使用するときにグリッドの子に直接マージンを明示的に設定した場合、そのマージンはデザイナーには表示されますが、実行時には表示されないことに注意してください。
このプロパティは、Grid、StackPanel、WrapPanel、UniformGrid、またはPanelの他の子孫に適用できます。それは直接の子供に影響を与えます。子どもたちは自分のコンテンツのレイアウトを管理したいと思うでしょう。
PanelExt.cs
public static class PanelExt
{
public static Thickness? GetChildMargin(Panel obj)
{
return (Thickness?)obj.GetValue(ChildMarginProperty);
}
public static void SetChildMargin(Panel obj, Thickness? value)
{
obj.SetValue(ChildMarginProperty, value);
}
/// <summary>
/// Apply a fixed margin to all direct children of the Panel, overriding all other margins.
/// Panel descendants include Grid, StackPanel, WrapPanel, and UniformGrid
/// </summary>
public static readonly DependencyProperty ChildMarginProperty =
DependencyProperty.RegisterAttached("ChildMargin", typeof(Thickness?), typeof(PanelExt),
new PropertyMetadata(null, ChildMargin_PropertyChanged));
private static void ChildMargin_PropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var target = d as Panel;
target.Loaded += (s, e2) => ApplyChildMargin(target, (Thickness?)e.NewValue);
ApplyChildMargin(target, (Thickness?)e.NewValue);
}
public static void ApplyChildMargin(Panel panel, Thickness? margin)
{
int count = VisualTreeHelper.GetChildrenCount(panel);
object value = margin.HasValue ? margin.Value : DependencyProperty.UnsetValue;
for (var i = 0; i < count; ++i)
{
var child = VisualTreeHelper.GetChild(panel, i) as FrameworkElement;
if (child != null)
{
child.SetValue(FrameworkElement.MarginProperty, value);
}
}
}
}
デモ：
MainWindow.xaml
<Grid
local:PanelExt.ChildMargin="2"
x:Name="MainGrid"
>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Rectangle Width="100" Height="40" Fill="Red" Grid.Row="0" Grid.Column="0" />
<Rectangle Width="100" Height="40" Fill="Green" Grid.Row="1" Grid.Column="0" />
<Rectangle Width="100" Height="40" Fill="Blue" Grid.Row="1" Grid.Column="1" />
<Button Grid.Row="2" Grid.Column="0" Click="NoMarginClick">No Margin</Button>
<Button Grid.Row="2" Grid.Column="1" Click="BigMarginClick">Big Margin</Button>
<ComboBox Grid.Row="3" Grid.Column="0" Grid.ColumnSpan="2" />
</Grid>
MainWindow.xaml.cs
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void NoMarginClick(object sender, RoutedEventArgs e)
{
// In real life, if we wanted to change PanelExt.ChildMargin at runtime, we
// would prefer to bind it to something, probably a dependency property of
// the view. But this will do for a demonstration.
PanelExt.SetChildMargin(MainGrid, null);
}
private void BigMarginClick(object sender, RoutedEventArgs e)
{
PanelExt.SetChildMargin(MainGrid, new Thickness(20));
}
}
