WorkIndicator/UsbService.cs

using System;
using System.Windows.Forms;

namespace WorkIndicator;

internal class UsbService : NativeWindow, IDisposable
{
    public event Action DevicesChanged;

    private const int WmDeviceChange = 0x0219;
    private const int DbtDeviceArrival = 0x8000;
    private const int DbtDeviceRemoveComplete = 0x8004;
    private const int DbtDevNodesChanged = 0x0007;

    private bool _isDisposed;

    internal UsbService()
    {
        base.CreateHandle(new CreateParams());
    }

    protected override void WndProc(ref Message msg)
    {
        base.WndProc(ref msg);

        if (msg.Msg != WmDeviceChange)
            return;

        switch (msg.WParam.ToInt32())
        {
            case DbtDevNodesChanged:
            case DbtDeviceArrival:
            case DbtDeviceRemoveComplete:
                DevicesChanged?.Invoke();
                break;
        }
    }

    public void Dispose()
    {
        if (_isDisposed)
            return;

        base.DestroyHandle();

        _isDisposed = true;

        GC.SuppressFinalize(this);
    }
}