Single instance

By default, Tharga.Wpf allows multiple instances of an application to run side-by-side. Set AllowMultipleApplications = false to enforce a single instance:

protected override void Options(ThargaWpfOptions options)
{
    options.AllowMultipleApplications = false;
}

What happens on second launch

1. A second instance starts.
2. It detects the running instance via a named-mutex lock.
3. It signals the running instance to show itself — even if hidden in the system tray, the main window is restored and brought to the foreground.
4. The second instance exits without showing UI.

The user perceives a "click the shortcut to bring my app back" experience instead of a second window opening.

Interaction with Velopack updates

The single-instance lock is automatically released before a Velopack restart. This avoids a deadlock where the updated process tries to start while the old process still holds the lock. The release happens in ApplicationUpdateStateServiceBase.BeforeRestartAsync() — you don't need to do anything special when you opt into single-instance mode plus Velopack updates.

Choosing the lock name

The lock is keyed off ApplicationShortName. Two applications with the same short name (e.g. two builds of the same product) will see each other; two applications with different short names will not. Set this in Options:

protected override void Options(ThargaWpfOptions options)
{
    options.ApplicationShortName = "MyApp";
    options.AllowMultipleApplications = false;
}