C# .net code error message in calculator code : 
**I am coding for calculator in c#.net. I am having an error message on txtDisplay in txtDisplay.Text. the error says "The name 'txtDisplay' does not exists in the current context".My code so far is:** 


using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

namespace Calc

{
  
  public partial class Form1 : Form
    {

       
 public Form1()
        {

            InitializeComponent();
       
 }

        private void btnOne_Click(object sender, EventArgs e)
        {
            txtDisplay.Text = txtDisplay.Text + btnOne.Text;

        }