How to make the listbox items orientation to horizontal in the default styling of a listbox. What i mean by default is the style which we get using blend.
Use the ItemsPanel property to replace the panel with a horizontal StackPanel:
<ListBox>
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
If you want to do this in a Style, just add a Setter that sets the ItemsPanel property:
<Style TargetType="ListBox">
<!-- Rest of the style -->
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</Setter.Value>
</Setter>
</Style>