Login Button using MySQL w/ Parameters

        #region Program Security
        public class Security
        {
            public static string HashCode(string str)
            {
                string rethash = "";
                try
                {
                    System.Security.Cryptography.SHA1 hash = System.Security.Cryptography.SHA1.Create();
                    System.Text.ASCIIEncoding encoder = new System.Text.ASCIIEncoding();
                    byte[] combined = encoder.GetBytes(str);
                    hash.ComputeHash(combined);
                    rethash = BitConverter.ToString(hash.Hash).Replace("-", "");
                }
                catch (Exception ex)
                {
                    string strerr = "Error in HashCode : " + ex.Message;
                }
                return rethash;
            }
        }
        #endregion

        private void btnLogin_Click(object sender, EventArgs e)
        {
            try
            {
                using (MySqlConnection myConn = new MySqlConnection(strConnect))
                using (MySqlCommand selectCommand = new MySqlCommand())
                {
                    string hashedvalue = Security.HashCode(txtPassword.Text);
                    selectCommand.CommandText = "SELECT * FROM database WHERE column1=@User AND column2=@Password";
                    selectCommand.Connection = myConn;
                    selectCommand.Parameters.Add("@User", MySqlDbType.VarChar).Value = txtUsername.Text;
                    selectCommand.Parameters.Add("@Password", MySqlDbType.VarChar).Value = hashedvalue;
                    myConn.Open();
                    MySqlDataReader myReader;
                    object result = selectCommand.ExecuteScalar();
                    if (result != null)
                    {
                        myReader = selectCommand.ExecuteReader();
                        int count = Convert.ToInt32(result);
                        bool IsAdminUser = false;
                        while (myReader.Read())
                        {
                            count = count + 1;
                            IsAdminUser = myReader["rank"].ToString().Equals("admin");
                        }
                        if (count > 0 && IsAdminUser == true)
                        {
                            this.Hide();
                            admin.Show();
                        }
                        else if (count > 0)
                        {
                            this.Hide();
                            management.Show();
                        }
                        else
                            MessageBox.Show("Incorrect Username or Password");
                    }
                    else
                    {
                        MessageBox.Show("Incorrect Username or Password");
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }