using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApp
{
    public class TransparentTabControl : TabControl
    {
        private List<Panel> pages = new List<Panel>();

        public void MakeTransparent()
        {
            if (TabCount == 0) throw new InvalidOperationException();
            var height = GetTabRect(0).Bottom;
            // Move controls to panels
            for (int tab = 0; tab < TabCount; ++tab)
            {
                var page = new Panel
                {
                    Left = this.Left,
                    Top = this.Top + height,
                    Width = this.Width,
                    Height = this.Height - height,
                    BackColor = Color.Transparent,
                    Visible = tab == this.SelectedIndex
                };
                for (int ix = TabPages[tab].Controls.Count - 1; ix >= 0; --ix)
                {
                    TabPages[tab].Controls[ix].Parent = page;
                }
                pages.Add(page);
                this.Parent.Controls.Add(page);
            }
            this.Height = height /* + 1 */;
        }

        protected override void OnSelectedIndexChanged(EventArgs e)
        {
            base.OnSelectedIndexChanged(e);
            for (int tab = 0; tab < pages.Count; ++tab)
            {
                pages[tab].Visible = tab == SelectedIndex;
            }
        }

        protected override void Dispose(bool disposing)
        {
            if (disposing) foreach (var page in pages) page.Dispose();
            base.Dispose(disposing);
        }
        protected override CreateParams CreateParams
        {
            get
            {
                var parms = base.CreateParams;
                parms.Style &= ~0x02000000;  // Turn off WS_CLIPCHILDREN
                return parms;
            }
        }
    }
}