ResourceListTreeViewItem.xaml

<TreeViewItem x:Class="UndertaleModTool.ResourceListTreeViewItem"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:UndertaleModTool"
             xmlns:undertalelib="clr-namespace:UndertaleModLib;assembly=UndertaleModLib"
             mc:Ignorable="d">

    <TreeViewItem.Resources>
        <local:ImplementsInterfaceConverter x:Key="ImplementsInterfaceConverter"/>

        <DataTemplate x:Key="NullResourceItemTemplate">
            <TextBlock Text="(null)"/>
        </DataTemplate>

        <local:ContextMenuDark x:Key="UndertaleResourceMenu" Opened="MenuItem_ContextMenuOpened">
            <MenuItem Header="Open in new tab" Click="MenuItem_OpenInNewTab_Click"/>
            <MenuItem Header="Find all references" Click="MenuItem_FindAllReferences_Click"/>
            <MenuItem Header="Copy name to clipboard" Click="MenuItem_CopyName_Click"/>
            <MenuItem Header="Delete" Click="MenuItem_Delete_Click"/>
        </local:ContextMenuDark>

        <!-- TODO: Would need some way to know the ID, IndexOf won't be reliable
        <local:ContextMenuDark x:Key="NullResourceItemReplaceMenu" Opened="MenuItem_ContextMenuOpened_NullItem">
            <MenuItem IsEnabled="False" Header="ID: " Name="ObjectIdLabel" />
            <Separator />
            <MenuItem Header="_Add in place" />
        </local:ContextMenuDark>
        -->

        <Style x:Key="ResourceListTreeViewItem.ItemContainerStyle" TargetType="{x:Type TreeViewItem}">
            <Style.Triggers>
                <DataTrigger Binding="{Binding ., Converter={StaticResource ImplementsInterfaceConverter}, ConverterParameter={x:Type undertalelib:UndertaleResource}}" Value="True">
                    <Setter Property="ContextMenu" Value="{StaticResource UndertaleResourceMenu}"/>
                </DataTrigger>
                <DataTrigger Binding="{Binding .}" Value="{x:Null}">
                    <Setter Property="Foreground" Value="Gray"/>
                    <!--<Setter Property="ContextMenu" Value="{StaticResource NullResourceItemReplaceMenu}"/>-->
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </TreeViewItem.Resources>

    <TreeViewItem.ItemContainerStyle>
        <StaticResource ResourceKey="ResourceListTreeViewItem.ItemContainerStyle"/>
    </TreeViewItem.ItemContainerStyle>

</TreeViewItem>