wpf-notifyicon/Source/Windowless Sample/App.xaml

<Application x:Class="Windowless_Sample.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             ShutdownMode="OnExplicitShutdown">
    <Application.Resources>

        <!--
            Note that this application does not have a StartupUri declared, so no Window is automatically loaded.
            Also, the ShutdownMode was set to explicit, so we have to close the application programmatically
        -->
        
        
        <!-- merge NotifyIcon and related stuff into the application -->
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="NotifyIconResources.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>

    </Application.Resources>
</Application>