wpf scrollviewer mousewheel not working with stackpanel

Question

I have a stackpanel wrapped with a scrollviewer. inside the stackpanel I've some grids and inside the grids there're stackpanels again and some tiles control by MahApps Metro.

the scrollviewer is working fine if I drag the scrollbar. but mousewheel not working. may be some control is stealing the mousewheel action but I can't feagure out which one. I've tried to scroll mouse wheel while focusing on the scrollbar. but it's still not working.

<ScrollViewer x:Name="TS" Grid.Row="1" HorizontalAlignment="Stretch" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Disabled" CanContentScroll="True" PanningMode="HorizontalOnly" SnapsToDevicePixels="True" Background="Transparent">
    <StackPanel x:Name="TilesPanel" VerticalAlignment="Top" HorizontalAlignment="Stretch" Orientation="Horizontal">
        <StackPanel.Resources>
            <Style TargetType="{x:Type Grid}">
                <Setter Property="Margin" Value="0,50,0,0"/>
            </Style>
        </StackPanel.Resources>
        <Separator Background="{x:Null}" Width="110"></Separator>
        <Grid>
            <StackPanel>
                <StackPanel Orientation="Horizontal">
                    <StackPanel.Resources>
                        <Style TargetType="{x:Type Grid}">
                            <Setter Property="Margin" Value="10,0,0,0"/>
                        </Style>
                    </StackPanel.Resources>
                    <Grid Height="260">
                        <StackPanel>
                            <StackPanel.Resources>
                                <Style TargetType="{x:Type StackPanel}">
                                    <Setter Property="Margin" Value="0,0,0,10"/>
                                </Style>
                            </StackPanel.Resources>
                        <StackPanel Width="247" Height="119">
                            <Custom:Tile x:Name="Mail" Margin="0" Width="auto" d:LayoutOverrides="Height">
                                <Image Stretch="Fill" Source="Res/AppTiles/Mail.png"/>
                            </Custom:Tile>
                        </StackPanel>

                        //and it goes on like this//

                        </grid>
                      </stackpanel>
                <Separator Background="{x:Null}" Width="50"/>
            </Grid>
    </StackPanel>
    </ScrollViewer>

Is the grid that's coming in the way? Or is there any other way to use mousewheel in Horizontal Scrollviewer? I just can't figure out. please help.

Answer 1

Yes I figured that out. and solved it in the minimal way like this.

<ScrollViewer x:Name="TS" Grid.Row="1" HorizontalAlignment="Stretch" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Disabled" CanContentScroll="True" PanningMode="HorizontalOnly" SnapsToDevicePixels="True" Background="Transparent" PreviewMouseWheel="TS_PreviewMouseWheel">

added PreviewMouseWheel="TS_PreviewMouseWheel"

and in the code behind,

private void TS_PreviewMouseWheel(object sender, MouseWheelEventArgs e)
    {
        TS.HorizontalScrollBarVisibility = ScrollBarVisibility.Visible;
        ScrollViewer scrollviewer = sender as ScrollViewer;
        if (e.Delta > 0)
        {
            scrollviewer.LineLeft();
        }
        else
        {
            scrollviewer.LineRight();
        }
        e.Handled = true;
 }

thanks anyway.

Answer 2

usually a mouse have only one scroll wheel which is assigned for vertical scroll. I assume same for your case.

based on your code it seems like you want to perform a horizontal scroll by the mouse wheel.

I propose a solution using Attached properties

sample xaml

<ScrollViewer x:Name="TS"
              Grid.Row="1"
              HorizontalAlignment="Stretch"
              HorizontalScrollBarVisibility="Auto"
              VerticalScrollBarVisibility="Disabled"
              CanContentScroll="False"
              PanningMode="HorizontalOnly"
              SnapsToDevicePixels="True"
              Background="Transparent"
              l:ScrollViewerExtensions.IsHorizontalScrollOnWheelEnabled="true">

I have attached ScrollViewerExtensions.IsHorizontalScrollOnWheelEnabled to the scroll viewer which will enable horizontal scrolling via mouse wheel. also remember to set CanContentScroll="False", it is needed in your case.

ScrollViewerExtensions class

namespace CSharpWPF
{
    class ScrollViewerExtensions : DependencyObject
    {
        public static bool GetIsHorizontalScrollOnWheelEnabled(DependencyObject obj)
        {
            return (bool)obj.GetValue(IsHorizontalScrollOnWheelEnabledProperty);
        }

        public static void SetIsHorizontalScrollOnWheelEnabled(DependencyObject obj, bool value)
        {
            obj.SetValue(IsHorizontalScrollOnWheelEnabledProperty, value);
        }

        // Using a DependencyProperty as the backing store for IsHorizontalScrollOnWheelEnabled.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty IsHorizontalScrollOnWheelEnabledProperty =
            DependencyProperty.RegisterAttached("IsHorizontalScrollOnWheelEnabled", typeof(bool), typeof(ScrollViewerExtensions), new PropertyMetadata(false, OnIsHorizontalScrollOnWheelEnabledChanged));

        private static void OnIsHorizontalScrollOnWheelEnabledChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            ScrollViewer sv = d as ScrollViewer;
            if ((bool)e.NewValue)
                sv.PreviewMouseWheel += sv_PreviewMouseWheel;
            else
                sv.PreviewMouseWheel -= sv_PreviewMouseWheel;
        }

        static void sv_PreviewMouseWheel(object sender, MouseWheelEventArgs e)
        {
            ScrollViewer scrollviewer = sender as ScrollViewer;
            if (e.Delta > 0)
                scrollviewer.LineLeft();
            else
                scrollviewer.LineRight();
            e.Handled = true;
        }
    }
}

whole idea is to listen to the mouse wheel and scroll left or right based on the wheel delta (rotation)