Why Am I Getting Error Using TransactionScope?

Hi, Everybody!

I am having trouble with TransactionScope. I want my web method to be transactional. If any exception occurs, I want all database changes rolled back. Otherwise, commit. Please see error message below.

System.ApplicationException: Error in someClass :: Method public returnType methodName(parameterType parameter) :
System.ApplicationException: Error in someClass :: Method private string someMethod() :
System.Data.Odbc.OdbcException (0x80131937):
ERROR [08003] [Sybase][ODBC Driver]Connection not open
at System.Data.Odbc.OdbcConnection.Open_EnlistTransaction(Transaction transaction)
at System.Data.Odbc.OdbcConnectionOpen.EnlistTransaction(Transaction transaction)
at System.Data.Odbc.OdbcConnection.EnlistTransaction(Transaction transaction)
at System.Data.Odbc.OdbcConnection.Open()
at someNameSpace.someMethod() in c:\somePath\someClass.cs:line 35

The following is an excerpt of my code. What am I doing wrong?

        [WebMethod]
        public returnType methodName(parameterType parameter)
        {
            using (var transactionScope = new TransactionScope(TransactionScopeOption.RequiresNew))
            {
                try
                {
                    var someValue = someMethod();
                        :
                        :
                        :

                    transactionScope.Complete();

                    return response;
                }
                catch (Exception ex)
                {
                    return ErrorMessages(ex);
                }
            }
        }

        private string someMethod()
        {
            var commandText = "...some valid SQL expression...";
            var commandType = CommandType.Text;

            try
            {
                using (var odbcConnection = new OdbcConnection(DefaultDbConnection.ToString()))
                {
                    using (var odbcCommand = new OdbcCommand(commandText, odbcConnection))
                    {
                        odbcConnection.Open();  // Exception is thrown here!
                        odbcCommand.CommandType = commandType;

                        using (var reader = odbcCommand.ExecuteReader())
                        {
                            reader.Read();
                            return reader.GetString(0);
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                throw new ApplicationException("Error in someMethod.", ex);
            }
        }

Thank-you in advance for your help!