WPF

<Style TargetType="{x:Type TabItem}">
    <Setter Property="ContextMenu">
        <Setter.Value>
            <ContextMenu>
                <MenuItem Header="Close"
                            Command="{Binding CloseTabCommand}" 
                            CommandParameter="{Binding Path=PlacementTarget, RelativeSource={RelativeSource AncestorType=ContextMenu}}"/>
            </ContextMenu>
        </Setter.Value>
    </Setter>

private ICommand _CloseTabCommand;
public ICommand CloseTabCommand
{
    get
    {
        if (_CloseTabCommand == null)
            _CloseTabCommand = new RelayCommand<object>(p => closeTabExecuted(p), p => closeTabCanExecute(p));

        return _CloseTabCommand;
    }
}

private bool closeTabCanExecute(object obj)
{
    return true;
}
private void closeTabExecuted(object obj)
{
    TabManager.CloseActiveTab();
}