Execute stored procedure and get return value, using NHibernate session

NHibernateSqlProcedureHelper.cs

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using NHibernate;

namespace NHibernate.Helpers
{
    public static class SqlProcedureHelper
    {
        public static int ExecuteWithReturn(this ISession session, ProcedureQuery query)
        {
            using (var ts = session.BeginTransaction())
            {
                var command = new SqlCommand {Connection = (SqlConnection) session.Connection};
                ts.Enlist(command);

                command.CommandType = CommandType.StoredProcedure;
                command.CommandText = query.Procedure;

                command.Parameters.AddRange(query.Parameters.ToArray());

                var returnParameter = new SqlParameter("@RETURN_VALUE", SqlDbType.Int)
                {
                    Direction = ParameterDirection.ReturnValue
                };
                command.Parameters.Add(returnParameter);

                command.ExecuteNonQuery();
                ts.Commit();
                return Convert.ToInt32(returnParameter.Value);
            }
        }
    }

    public class ProcedureQuery
    {
        public ProcedureQuery(string procedure)
        {
            Procedure = procedure;
            Parameters = new List<SqlParameter>();
        }

        public string Procedure { get; private set; }
        public List<SqlParameter> Parameters { get; private set; }

        public void AddInt32(string name, int value)
        {
            AddParameter(name, SqlDbType.Int, value);
        }

        public void AddDecimal(string name, decimal value)
        {
            AddParameter(name, SqlDbType.Decimal, value);
        }

        private void AddParameter(string name, SqlDbType type, object value)
        {
            var parameter = new SqlParameter("@" + name, type)
            {
                Direction = ParameterDirection.Input,
                Value = value
            };
            Parameters.Add(parameter);
        }

    }
}