Encryption & Decryption MD5 C#

Decrypt.cs

private void btnDecrypt_Click(object sender, EventArgs e)
        {
            byte[] data = Convert.FromBase64String(textBox4.Text); // decrypt the incrypted text
            using (MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider())
            {
                byte[] keys = md5.ComputeHash(UTF8Encoding.UTF8.GetBytes(hash));
                using (TripleDESCryptoServiceProvider tripDes = new TripleDESCryptoServiceProvider() { Key = keys, Mode = CipherMode.ECB, Padding = PaddingMode.PKCS7 })
                {
                    ICryptoTransform transform = tripDes.CreateDecryptor();
                    byte[] results = transform.TransformFinalBlock(data, 0, data.Length);
                    textBox4.Text = UTF8Encoding.UTF8.GetString(results);
                }
            }
        }

Encrypt.cs

private void btnEncrypt_Click(object sender, EventArgs e)
        {
            byte[] data = UTF8Encoding.UTF8.GetBytes(textBox3.Text);
            using (MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider())
            {
                byte[] keys = md5.ComputeHash(UTF8Encoding.UTF8.GetBytes(hash));
                using (TripleDESCryptoServiceProvider tripDes = new TripleDESCryptoServiceProvider() { Key = keys, Mode = CipherMode.ECB, Padding = PaddingMode.PKCS7 })
                {
                    ICryptoTransform transform = tripDes.CreateEncryptor();
                    byte[] results = transform.TransformFinalBlock(data, 0, data.Length);
                    textBox4.Text = Convert.ToBase64String(results, 0, results.Length);
                }
            }
        }

byte[] keys = md5.ComputeHash(UTF8Encoding.UTF8.GetBytes(hash));

whats the value of hash

byte[] keys = md5.ComputeHash(UTF8Encoding.UTF8.GetBytes(hash));

whats the value of hash

static string hash { get; set; } = "A!9HHhi%XjjYY4YP2@Nob009X";

in file Encrypt.cs
line 2: use textBox4.Text instead of textBox3.Text

public static string Encrypt(string value)
{
var md5 = new MD5CryptoServiceProvider();
var hash = md5.ComputeHash(Encoding.UTF8.GetBytes(value));

        //converting the contents of the hash variable from byte[] to string
        var result = string.Empty;
        foreach (var item in hash)
        {
            result += item.ToString("X2"); //X2 -> HEXADECIMAL
        }
        return result.ToUpper();
    }