private void doneButton_Click(object sender, EventArgs e) {
    string userName = userNameTextBox.Text,
        password = passwordTextBox.Text,
        question = questionMenu.Text,
        answer = answerTextBox.Text;
        int key = EncryptionClass.generateKey();

    SqlConnection connection = SQLHelper.GetConnection();
    String sqlQuery = "INSERT INTO dbo.Account(UserName, UserPassword, UserKey) " +
       "VALUES ('" + userName + "', '" + EncryptionClass.encrypt(password, key) + "', " + key + ");";

    Console.WriteLine("string " + sqlQuery);
    //INSERT INTO dbo.Account(UserName, UserPassword, UserKey) VALUES ('somename', 'Lysjehqcqhe01', 16);
    SQLHelper.ExecuteNonQuery(sqlQuery, connection);
}

namespace Assign6 {
    class SQLHelper {
        public static SqlConnection GetConnection() {
            SqlConnection connection = new SqlConnection(@"Data Source=(LocalDB)MSSQLLocalDB;AttachDbFilename=|DataDirectory|MyData.mdf;Integrated Security=True");

            connection.Open();
            return connection;
        }

        public static void ExecuteNonQuery(string sqlQuery, SqlConnection connection) {
            using (SqlCommand command = new SqlCommand(sqlQuery, connection)) {
                try {
                    command.ExecuteNonQuery();
                }
                finally {
                    connection.Close();
                }
            }
        }
   }
}

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
    </configSections>
    <connectionStrings>
        <add name="Assign6.Properties.Settings.MyDataConnectionString"
            connectionString="Data Source=(LocalDB)MSSQLLocalDB;AttachDbFilename=|DataDirectory|MyData.mdf;Integrated Security=True"
            providerName="System.Data.SqlClient" />
    </connectionStrings>
    <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" />
    </startup>
</configuration>