Virtual Desktop Number Indicator

A lightweight Windows tray app that shows which virtual desktop you're on as a number in the system tray. The number updates instantly when you switch desktops (e.g. Win+Ctrl+← / →).

The number is drawn as large white digits with a black outline (subtitle style), so it stays readable on any taskbar color — light or dark.

Features

• Live desktop number in the tray, updated the moment you switch.
• Tooltip shows position and desktop name, e.g. Desktop 7/8 — Work.
• Start with Windows toggle (right-click the tray icon).
• Single instance — launching again does nothing.

Requirements

• Windows 10 or 11.
• .NET 10 SDK to build (a published single-file exe only needs the .NET 10 Desktop Runtime, or nothing if built self-contained).

Build

Quick build:

dotnet build -c Release

The executable lands in bin\Release\net10.0-windows\VirtualDesktopNumberIndicator.exe.

Publish a single portable .exe

Framework-dependent (small; needs the .NET 10 Desktop Runtime installed):

dotnet publish -c Release -r win-x64 --self-contained false -p:PublishSingleFile=true

Self-contained (larger; runs on any Windows 10/11 with no runtime installed):

dotnet publish -c Release -r win-x64 --self-contained true -p:PublishSingleFile=true

Output: bin\Release\net10.0-windows\win-x64\publish\VirtualDesktopNumberIndicator.exe.

Run

Just run the .exe. It shows an icon in the tray with the current desktop number.

Make it always visible: Windows hides new tray icons in the overflow (^) by default and apps can't force them out. On first run a notification reminds you — drag the number from the overflow onto the taskbar once, or go to Settings ▸ Personalization ▸ Taskbar ▸ Other system tray icons and turn it on. Windows remembers the choice.

To start it automatically at login, right-click the tray icon and enable Start with Windows.

To quit, right-click the tray icon and choose Exit.

How it works

The app reads the current virtual desktop from the registry rather than using undocumented COM APIs, so it stays stable across Windows updates:

• Current desktop GUID: HKCU\...\Explorer\VirtualDesktops → CurrentVirtualDesktop (falls back to the per-session SessionInfo\<id>\VirtualDesktops key on older builds).
• Ordered desktop list: HKCU\...\Explorer\VirtualDesktops → VirtualDesktopIDs (the current GUID's index in this list + 1 is the number shown).
• Names: HKCU\...\Explorer\VirtualDesktops\Desktops\{GUID} → Name.

Updates are pushed via RegNotifyChangeKeyValue (instant), with a 1-second polling fallback as a safety net.

Project layout

File	Purpose
Program.cs	Entry point, single-instance mutex.
TrayAppContext.cs	Tray icon, context menu, wiring.
DesktopWatcher.cs	Registry reads + change notifications.
IconRenderer.cs	Renders the number into a tray icon.
StartupManager.cs	"Start with Windows" registry entry.
app.manifest	Windows 10/11 + per-monitor DPI awareness.