C# Windows form application that records time spent on all application

I have code for firefox that shows how much time I spent in it when it is active window

[DllImport("user32.dll")]
private static extern IntPtr GetForegroundWindow();

    [DllImport("user32.dll", SetLastError = true)]
    static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);

    private TimeSpan fireFoxElapsedTime = new TimeSpan();

    private void timer1_Tick(object sender, EventArgs e)
    {
        var wnd = GetForegroundWindow();
        uint procId;
        GetWindowThreadProcessId(wnd, out procId);

        var process = Process.GetProcessById((int)procId);
        if (process.ProcessName.Equals("firefox", StringComparison.CurrentCultureIgnoreCase))
            {
            fireFoxElapsedTime += new TimeSpan(0, 0, 0, 0, timer1.Interval);
             }
        label2.Text = fireFoxElapsedTime.ToString();
    }

I need for all the applications whichever is active and data should be stored in sqlite