where to dispose of TextEditingController in a stateless widget?

I am using provider for flutter state management, and I have this code that allows editing a property by using a dialog with a text field.

TextButton(
  onPressed: () async {
    final _textController = TextEditingController();
    final result = await showDialog(
      context: context,
      builder: (context) {
        return AlertDialog(
          title: const Text('....'),
          content: TextField(
            controller: _textController,
            actions: [
              TextButton(
                child: const Text('Cancel'),
                  onPressed: () {
                    Navigator.pop(context);
                  },
              ),
              TextButton(
                child: const Text('Add'),
                onPressed: () {
                  Navigator.pop(context, _textController.text);
                },
              ),
            ],
        );
      },
    );
    if (result != null) {
      context.read<PatientProvider>().updatePatientName(result as String);
    }
  },
  child: Text(
    context.watch<PatientProvider>().patient.name
  ),
)

Where do I dispose of _textController?

Dispose the _textController after alert dialoge. After await showDialog, the dialog is closed, and we dispose of the controller right away.

_textController.dispose();

Full solution:

TextButton(
  onPressed: () async {
    final _textController = TextEditingController();
    final result = await showDialog(
      context: context,
      builder: (context) {
        return AlertDialog(
          title: const Text('....'),
          content: TextField(
            controller: _textController,
            actions: [
              TextButton(
                child: const Text('Cancel'),
                  onPressed: () {
                    Navigator.pop(context);
                  },
              ),
              TextButton(
                child: const Text('Add'),
                onPressed: () {
                  Navigator.pop(context, _textController.text);
                },
              ),
            ],
        );
      },
    );
 
    // Dispose the controller after alert dialog is closed.
    _textController.dispose();

    if (result != null) {
      context.read<PatientProvider>().updatePatientName(result as String);
    }
  },
  child: Text(
    context.watch<PatientProvider>().patient.name
  ),
)