How to reducec space between parent and node in treeview

Question

How to reduce the vertical spacing between parent and child nodes.

I tried this but doesn't work.

<asp:TreeView ID="TreeViewArtMaterial" runat="server" EnableViewState="true"

width="250px" SkinID="NoImage"

onDataBound="TreeViewArtMaterial_DataBound"

ParentNodeStyle-ChildNodesPadding="0" ParentNodeStyle-VerticalPadding="0" ParentNodeStyle-NodeSpacing="0"

DataSourceID="SiteMapDataSource1" ExpandDepth=1>

<SelectedNodeStyle Font-Bold="true" ForeColor="#249c98" VerticalPadding="0" NodeSpacing="0" />

</asp:TreeView>