Question

I want to write to a log every 3 hours using System.IO

There is no matter how the files called. Really, just how can I do that every 3 hours something happens?

Answer 1

Use a Timer, set its Interval to 3*60*60*1000 and, in Tick event, do what you need.
Remember to stop timer and remove the handler before form or app closing…

public partial class Form1 : Form
{
    Timer timer = null;

    public Form1()
    {
        InitializeComponent();

        timer = new Timer();
        timer.Interval = 3 * 60 * 60 * 1000;
        timer.Tick += new EventHandler(timer_Tick);
        timer.Enabled = true;
    }

    void timer_Tick(object sender, EventArgs e)
    {
        // Do what you need
        File.AppendAllText(log_file, your_message);

    }

    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
        timer.Stop();
        timer.Tick -= timer_Tick;
    }
}