xmlns:wu="clr-namespace:WpfUtility;assembly=WpfUtility"

<ResourceDictionary Source="/WpfUtility;component/PaneledTab.xaml" />

<wu:PaneledTab x:Name="paneledTab">
  <wu:PaneledTab.FormerPanel>
    <WrapPanel>
      <Button x:Name="button_Top" Content=" T " />
    </WrapPanel>
  </wu:PaneledTab.FormerPanel>
  <wu:PaneledTab.LatterPanel>
    <WrapPanel>
      <Button x:Name="button_Left" Content=" L " />
      <Button x:Name="button_Right" Content=" R " />
      <Button x:Name="button_Bottom" Content=" B " />
    </WrapPanel>
  </wu:PaneledTab.LatterPanel>
  <TabItem Header="Item1">
    <TextBlock Text="Item1" />
  </TabItem>
  <TabItem Header="Item2">
    <TextBlock Text="Item2" />
  </TabItem>
  <TabItem Header="Item3">
    <TextBlock Text="Item3" />
  </TabItem>
</wu:PaneledTab>