Execute program with hit on enter after write text and remove written

Question

I'm new, I found examples here, but nothing works proper for me.

I'm just trying execute my program second way, but not sure how to figure out.

I want write some phrase in textBox1, then hit on enter, remove written phrase from textBox1, make some calculations and only then show this text in textBox2

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

namespace XX_TEXTBOX_TEST
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }    
        private void textBox1_TextChanged(object sender, EventArgs e)
        {    
            textBox2.AppendText("OK!");   
        }
    }
}

if I go this way:

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

namespace XX_TEXTBOX_TEST
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }   
        private void textBox1_KeyDown(object sender, KeyEventArgs e)
        {    
            if (e.KeyCode == Keys.Enter)
            {
                textBox2.AppendText("OK!");
            }                   
        }
    }
}

I got error:

`Severity Code Description Project File Line Suppression State Error CS1061 'Form1' does not contain a definition for 'textBox1_TextChanged' and no extension method 'textBox1_TextChanged' accepting a first argument of type 'Form1' could be found (are you missing a using directive or an assembly reference?) XX_TEXTBOX_TEST C:\FOLDER\Form1.Designer.cs 42 Active

And:

Severity Code Description Project File Line Suppression State Message The designer cannot process unknown name 'textBox1_TextChanged' at line 42. The code within the method 'InitializeComponent' is generated by the designer and should not be manually modified. Please remove any changes and try opening the designer again. C:\FOLDER\Form1.Designer.cs 43

Answer 1

private void  textBox1_KeyDown(object sender, KeyEventArgs e)
    {
        if (e.KeyCode == Keys.Enter)
        {
            //your function 
        }
    }

you must use KeyDown event of textbox