Hello!
I read some similar posts,but i didn't found the "easy" solution.
My problem is ,i want more space between groups in gridview.
My XML code :
<Page
x:Class="App1.BlankPage2"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:App1"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d" Background="Black">
<Page.Resources>
<CollectionViewSource x:Name="cvs1" IsSourceGrouped="true" />
</Page.Resources>
<Grid VerticalAlignment="Stretch" HorizontalAlignment="Stretch" Background="Gray" >
<GridView x:Name="ItemsByCategory" VerticalAlignment="Center"
ItemsSource="{Binding Source={StaticResource cvs1}}"
BorderBrush="{StaticResource ApplicationForegroundThemeBrush}"
Padding="116,137,40,46"
>
<GridView.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" Margin="100"/>
</ItemsPanelTemplate>
</GridView.ItemsPanel>
<GridView.ItemTemplate>
<DataTemplate>
<Grid HorizontalAlignment="Stretch" Background="Green" >
<StackPanel Orientation="Horizontal" Margin="1,10,0,0">
<Image Source="{Binding Image}" Height="60" Width="60" VerticalAlignment="Center" Margin="0,0,10,0"/>
<StackPanel Margin="0,0,0,0" Orientation="Vertical" Width="100" Height="150">
<TextBlock TextWrapping="Wrap" Width="100" VerticalAlignment="Bottom" Text="{Binding Title}" HorizontalAlignment="Center" FontFamily="Segoe UI" />
</StackPanel>
</StackPanel>
</Grid>
</DataTemplate>
</GridView.ItemTemplate>
<!--- header -->
<GridView.GroupStyle>
<GroupStyle>
<GroupStyle.HeaderTemplate>
<DataTemplate>
<Grid >
<Button
AutomationProperties.Name="Group Title"
Style="{StaticResource TextPrimaryButtonStyle}">
<StackPanel Orientation="Horizontal">
<TextBlock Text='{Binding Key}' FontSize="30" Margin="5" Style="{StaticResource GroupHeaderTextStyle}"/>
</StackPanel>
</Button>
</Grid>
</DataTemplate>
</GroupStyle.HeaderTemplate>
<GroupStyle.Panel>
<ItemsPanelTemplate>
<VariableSizedWrapGrid Orientation="Vertical" Height="800" />
</ItemsPanelTemplate>
</GroupStyle.Panel>
</GroupStyle>
</GridView.GroupStyle>
</GridView>
<TextBlock HorizontalAlignment="Left" Margin="118,60,0,0" TextWrapping="Wrap" Text="Test" VerticalAlignment="Top" FontSize="60" Foreground="White"/>
</Grid>
</Page>

Thx,for any help !