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

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            CollapsiblePanel cp = new CollapsiblePanel();
            this.Controls.Add(cp);
        }
    }
    //
    public class CollapsiblePanel : SplitContainer
    {
        public Button OpenCloseButton;
        public TextBox TextBox;
        public CollapsiblePanel()
        {
            this.Orientation = Orientation.Horizontal;
            this.IsSplitterFixed = false;
            this.OpenCloseButton = new Button();
            this.OpenCloseButton.Dock = DockStyle.Fill;
            this.OpenCloseButton.Click += new EventHandler(_OpenCloseButton_Click);
            this.Panel1.Controls.Add(OpenCloseButton);
            this.TextBox = new TextBox();
            this.TextBox.Multiline = true;
            this.TextBox.Dock = DockStyle.Fill;
            this.Panel2.Controls.Add(TextBox);

        }

        void CollapsiblePanel_SizeChanged(object sender, EventArgs e)
        {
        }

        void _OpenCloseButton_Click(object sender, EventArgs e)
        {
            this.Panel2Collapsed = !this.Panel2Collapsed;
        }
    }
}