Extract information from inside a private event handler

 in a class: 

Form1 form1 = new Form1();
form1.Display(z);
 
in Form1 class:
 
public void Display(double number)
{
richTextBox1.AppendText(Convert.ToString(number));
}
 
 

 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
    {
        byte keynum = null;
        public Form1()
        {
            InitializeComponent();
        }


        private void Key_Click(object sender, EventArgs e)
        {
            Button currentkey = (Button)sender;
            //remove the word 'Key' from the name like from 'Key05'
            string currentKey = currentkey.Name.Remove(0, 3);
            this.keynum = Convert.ToByte(currentKey);
            textBox1.Text = Convert.ToString(keynum);

        }
    }
}