source: Common/RecentFiles.cs

using System;
using System.Collections.Generic;
using System.Windows.Forms;
using Microsoft.Win32;

namespace Common
{
    class RecentFiles
    {
        public List<string> Items = new List<string>();
        public int MaxCount = 10;
        public event EventHandler Change;
        public EventArgs e = null;

        public void AddItem(string fileName)
        {
            int index = Items.IndexOf(fileName);
            if (index != -1) Items.RemoveAt(index);
            Items.Insert(0, fileName);
            LimitMaxCount();
            DoChange();
        }

        public void LimitMaxCount()
        {
            while (Items.Count > MaxCount)
                Items.RemoveAt(Items.Count - 1);
        }

        public string GetFirstFileName()
        {
            if (Items.Count > 0) return Items[0];
            else return "";
        }

        private void DoChange()
        {
            Change?.Invoke(this, new EventArgs());
        }    

        public void LoadFromRegistry(string regSubKey)
        {
            RegistryKey regKey = Application.UserAppDataRegistry.OpenSubKey(regSubKey);
            if (regKey == null) regKey = Application.UserAppDataRegistry.CreateSubKey(regSubKey);

            int count = (int)regKey.GetValue("Count", 0);
            Items.Clear();
            for (int i = 0; i < count; i++)
            {
                Items.Add((string)regKey.GetValue("FileName" + i, ""));
            }
            DoChange();
        }

        public void SaveToRegistry(string regSubKey)
        {
            RegistryKey regKey = Application.UserAppDataRegistry.OpenSubKey(regSubKey, true);
            if (regKey == null) regKey = Application.UserAppDataRegistry.CreateSubKey(regSubKey);

            regKey.SetValue("Count", Items.Count);
            for (int i = 0; i < Items.Count; i++)
            {
                regKey.SetValue("FileName" + i, Items[i]);
            }
        }

        public void LoadToMenu(ToolStripMenuItem menuItem, EventHandler handler)
        {
            while (menuItem.DropDownItems.Count < Items.Count)
            {
                ToolStripMenuItem newItem = new ToolStripMenuItem();
                newItem.Click += handler;
                Theme.ApplyTheme(newItem);
                menuItem.DropDownItems.Add(newItem);
            }

            while (menuItem.DropDownItems.Count > Items.Count) menuItem.DropDownItems.RemoveAt(menuItem.DropDownItems.Count - 1);
            for (int i = 0; i < Items.Count; i++)
            {
                menuItem.DropDownItems[i].Text = Items[i];
            }
        }
    }
}