What is the easy way to set spacing between items in StackPanel?

Is there an easy way to set default space between items inside StackPanel开发者_开发知识库 so I'll don't have to set Margin property on each item?

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I use a transparent separator, which works well:

<Separator Opacity="0" Height="20"/>

You can of course use margins but then if you want to change the margins you have to update all of the elements.

The separator can even be styled in a static resource.

An attached property could do it too but I think it's overkill.

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if all the controls are the same then do as IanR suggested and implement a Style that catches that control. if it's not then you can't create a default style to a base class because it just won't work.

the best way for situations like these is to use a very neat trick - attached properties (aka Behaviors in WPF4)

you can create a class that has an attached property, like so:

public class MarginSetter
{
    public static Thickness GetMargin(DependencyObject obj)
    {
        return (Thickness)obj.GetValue(MarginProperty);
    }

    public static void SetMargin(DependencyObject obj, Thickness value)
    {
        obj.SetValue(MarginProperty, value);
    }

    // Using a DependencyProperty as the backing store for Margin.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty MarginProperty =
        DependencyProperty.RegisterAttached("Margin", typeof(Thickness), typeof(MarginSetter), new UIPropertyMetadata(new Thickness(), CreateThicknesForChildren));

    public static void CreateThicknesForChildren(object sender, DependencyPropertyChangedEventArgs e)
    {
        var panel = sender as Panel;

        if (panel == null) return;

        foreach (var child in panel.Children)
        {
            var fe = child as FrameworkElement;

            if (fe == null) continue;

            fe.Margin = MarginSetter.GetMargin(panel);
        }
    }


}

now, to use it, all you need to do is to attach this attached property to any panel you want, like so:

<StackPanel local:MarginSetter.Margin="10">
    <Button Content="hello " />
    <Button Content="hello " />
    <Button Content="hello " />
    <Button Content="hello " />
</StackPanel>

Completely reusable of course.

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<Rectangle Width="3"/>

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I find that creating a grid inside the stack panel, then adding the desired number of columns (or rows) as follows:

    <StackPanel Grid.Row="1" Grid.Column="0" Height="34" Width="698" Margin="10,5,10,10" Orientation="Horizontal"  HorizontalAlignment="Center" VerticalAlignment="Center" >
        <Grid Width="698" Margin="0,0,0,0">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>
            <Button x:Name="StartButton" Content="Start" Grid.Row="0" Grid.Column="0" Style="{StaticResource 3DButton}" HorizontalAlignment="Center" VerticalAlignment="Center" Width="70" Click="StartButton_Click" />
            <Button x:Name="HelpButton"  Content="Help"  Grid.Row="0" Grid.Column="1" Style="{StaticResource 3DButton}" HorizontalAlignment="Center" VerticalAlignment="Center" Width="70" Click="HelpButton_Click"  />
            <Button x:Name="ExitButton"  Content="Exit"  Grid.Row="0" Grid.Column="2" Style="{StaticResource 3DButton}" HorizontalAlignment="Center" VerticalAlignment="Center" Width="70" Click="ExitButton_Click" Foreground="Red" />
        </Grid>
    </StackPanel>

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The accepted answer doesn't work anymore. But I used that answer and the blog the author of that answer (Elad Katz) to make a working code (tested in .Net Core) that I reproduce here:

    public static class EstablecedorMargen { 


    public static Thickness GetMargen(DependencyObject objeto) => objeto != null ? (Thickness)objeto.GetValue(PropiedadMargen) : new Thickness();

    public static void SetMargen(DependencyObject objeto, Thickness value) => objeto?.SetValue(PropiedadMargen, value);

    public static readonly DependencyProperty PropiedadMargen 
        = DependencyProperty.RegisterAttached("Margen", typeof(Thickness), typeof(EstablecedorMargen), new UIPropertyMetadata(new Thickness(), Cambió));


    public static void Cambió(object sender, DependencyPropertyChangedEventArgs e) {
        if (!(sender is Panel panel)) return;
        panel.Loaded += new RoutedEventHandler(EstablecerMargenControlesHijos);
    } 


    public static void EstablecerMargenControlesHijos(object sender, RoutedEventArgs e) {

        if (!(sender is Panel panel)) return;
        foreach (var hijo in panel.Children) {
            if (!(hijo is FrameworkElement feHijo)) continue;
            feHijo.Margin = GetMargen(panel);
        }

    } 


} 

Then you use:

   <StackPanel local:EstablecedorMargen.Margen="10" >          
            <Button Content="1" />
            <Button Content="2" />
            <Button Content="3" />
    </StackPanel>