<class name="AST.PartnerSite20.Core.Domain.User, AST.PartnerSite20.Core.Dao">
        <id name="UserId" type="System.Int32" column="UserId" unsaved-value="0">
            <generator class="assigned"/>
        </id>
        <property name="ClientId" type="System.Int32" not-null="true" />
    ......
                 <sql-insert check="none">
            exec up_User_i @ClientId=?, @Login=?, @FirstName=?, @LastName=?, @Email=?, @Password=?, @UserId=?
        </sql-insert>

<sql-insert check="none">
[sql]

            exec up_User_i @ClientId=?, @Login=?, @FirstName=?, @LastName=?, @Email=?, @Password=?, @UserId=? output
[/sql]
</sql-insert>

CREATE PROCEDURE xsp_Ins_Person(
--<ParamDefBlock>
 @ID                              bigint                = null out
,@firstName                       varchar(254)          = null
,@lastName                        varchar(254)          = null
,@Debug                           bit                   = 0
--</ParamDefBlock>
)
AS
BEGIN
    SET NOCOUNT ON
    --<DeclareBlock>
    --<DeclareSysVarBlock>
    declare     
             @RET_CODE                int
            ,@ERROR_CODE            int
            ,@TRAN_CHECK            int
    --</DeclareSysVarBlock>
    --<DeclareVarBlock>
    --</DeclareVarBlock>
    --</DeclareBlock>
    --<PrepareTranBlock>
    set @TRAN_CHECK    = case when @@TRANCOUNT > 0 or @@OPTIONS & 2 > 0 then 1 else 0 end
    select    
             @RET_CODE        = 0
            ,@ERROR_CODE    = 0
    if @TRAN_CHECK = 0 BEGIN TRAN
    --</PrepareTranBlock>
    
    --<InsertBlock>
    INSERT INTO Person(firstName, lastName)
                VALUES(@firstName, @lastName)
    --</InsertBlock>
    
    set @ERROR_CODE = @@ERROR
    if (@ERROR_CODE <> 0) or (@RET_CODE <> 0) GOTO UNDO
    --<SuccBlock>
    SUCC:
        if (@TRAN_CHECK = 0) and (@@TRANCOUNT > 0) COMMIT TRAN
        set @ID = SCOPE_IDENTITY()
        SELECT @ID
        RETURN(0)
    --</SuccBlock>

    --<UndoBlock>
    UNDO:
        if (@@TRANCOUNT > 0)
            if @TRAN_CHECK = 0 ROLLBACK TRAN 
        RETURN(1)
    --</UndoBlock>
END

<?xml version="1.0" encoding="utf-8"?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="Enterprise.Employee, NHibernateStartLib" table="vEmployee">
<id name="ID" column="ID" type="Int32">
<generator class="identity" />
</id>
<version name="LastChangeLabel" column="LastChangeLabel" type="Byte[]" generated="always">
</version>
<property name="FirstName" />
<property name="LastName" />
<property name="Position" />
<property name="ID" />
<sql-insert>
          exec xsp_Ins_Employee
           @firstName                      = ?
          ,@lastName                       = ?
          ,@position                       = ?
          ,@Debug                          = 0
          ,@ID                             = ? out
</sql-insert>
</class>
</hibernate-mapping>

1. натягиваем ORM на существующую и работающую схему БД сильно завязанную на ХП.
   
2. ХП кроме вставки делает что-то в других таблицах не замапленых NH.
   
3. ХП вставляет не то, что мы передали, делая какие-то хитрые БЛ преобразования.

С><?xml version="1.0" encoding="utf-8"?>
С><hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
С><class name="Enterprise.Employee, NHibernateStartLib" table="vEmployee">
С><id name="ID" column="ID" type="Int32">
С><generator class="identity" />
С></id>
С><version name="LastChangeLabel" column="LastChangeLabel" type="Byte[]" generated="always">
С></version>
С><property name="FirstName" />
С><property name="LastName" />
С><property name="Position" />
С><property name="ID" />
С><sql-insert>
С>          exec xsp_Ins_Employee
С>           @firstName                      = ?
С>          ,@lastName                       = ?
С>          ,@position                       = ?
С>          ,@Debug                          = 0
С>          ,@ID                             = ? out
С></sql-insert>
С></class>
С></hibernate-mapping>
С>

public virtual IDbCommand GenerateCommand(CommandType type, SqlString sqlString, SqlType[] parameterTypes);

public class MySqlClientDriver : global::NHibernate.Driver.SqlClientDriver
    {
        private readonly string parameterPairPattern = @"@[^,]*";

        public override IDbCommand GenerateCommand(CommandType type, SqlString sqlString, SqlType[] parameterTypes)
        {
            IDbCommand command = base.GenerateCommand(type, sqlString, parameterTypes);
            string cmdSql = command.CommandText.ToLowerInvariant().Trim();

            ///Works only for stored procs
            if (cmdSql.StartsWith("exec", StringComparison.InvariantCulture))
            {
                cmdSql = cmdSql.Remove(0, 4).Trim();
                Regex regex = new Regex(parameterPairPattern);
                MatchCollection coll = regex.Matches(cmdSql);

                for (int i = 0; i < coll.Count; ++i)
                {
                    Match match = coll[i];
                    if (match.Value.EndsWith("out") || match.Value.EndsWith("output"))
                    {
                        ((IDbDataParameter) command.Parameters[i]).Direction = ParameterDirection.Output;
                    }
                }
            }
            return command;
        }

         /// <summary>
        /// Checks whether identifier is generated by output parameter or not
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public virtual bool IsIdentifierGeneratedByOutParameter(SqlCommandInfo sql)
        {
            string cmdSql = sql.Text.ToString().ToLowerInvariant().Trim();
            ///Works only for stored procs
            if (cmdSql.StartsWith("exec", StringComparison.InvariantCulture))
            {
                cmdSql = cmdSql.Remove(0, 4).Trim();
                Regex regex = new Regex(parameterPairPattern);
                MatchCollection coll = regex.Matches(cmdSql);
                if (coll.Count == 0)
                    return false;
                Match match = coll[coll.Count - 1]; ///Identifier match
                return match.Value.EndsWith("out") || match.Value.EndsWith("output");
            }
            return false;
        }
}

/// <summary>
        /// Persist an object, using a natively generated identifier
        /// </summary>
        protected object Insert(object[] fields, bool[] notNull, SqlCommandInfo sql, object obj,
                                ISessionImplementor session);

/// <summary>
        /// Persist an object, using a natively generated identifier
        /// </summary>
        protected object Insert(object[] fields, bool[] notNull, SqlCommandInfo sql, object obj,
                                ISessionImplementor session)
        {
            if (log.IsDebugEnabled)
            {
                log.Debug("Inserting entity: " + ClassName + " (native id)");
                if (IsVersioned)
                {
                    log.Debug("Version: " + Versioning.GetVersion(fields, this));
                }
            }

            try
            {
                bool useOutputParameterForId = false;
                SqlString insertSelectSQL = null;

                if (sql.CommandType == CommandType.Text)
                {
                    MySqlClientDriver driver = session.SessionFactory.ConnectionProvider.Driver as MySqlClientDriver;
                    if (driver != null && driver.IsIdentifierGeneratedByOutParameter(sql))
                    {
                        useOutputParameterForId = true;
                    }
                    else
                    {
                        insertSelectSQL =
                            Dialect.AddIdentitySelectToInsert(sql.Text, GetKeyColumns(0)[0], GetTableName(0));
                    }
                  
                }

                if (insertSelectSQL != null)
                {
                    // Use one statement to insert the row and get the generated id
                    IDbCommand insertSelect =
                        session.Batcher.PrepareCommand(CommandType.Text, insertSelectSQL, sql.ParameterTypes);

                    IDataReader rs = null;
                    try
                    {
                        // Well, it's always the first table to dehydrate, so pass 0 as the position
                        Dehydrate(null, fields, notNull, propertyColumnInsertable, 0, insertSelect, session, 0);
                        rs = session.Batcher.ExecuteReader(insertSelect);
                        return GetGeneratedIdentity(obj, session, rs);
                    }
                    finally
                    {
                        session.Batcher.CloseCommand(insertSelect, rs);
                    }
                }
                else
                {
                    // Do the insert
                    IDbCommand statement = session.Batcher.PrepareCommand(sql.CommandType, sql.Text, sql.ParameterTypes);
                    try
                    {
                        // Well, it's always the first table to dehydrate, so pass 0 as the position
                        Dehydrate(null, fields, notNull, propertyColumnInsertable, 0, statement, session, 0);
                        session.Batcher.ExecuteNonQuery(statement);
                        ProcessOutputParameters(null, fields, notNull, PropertyColumnInsertable, 0, statement, session,
                                                0,obj); // выставляет значениея пропертям класса, которые смаплены на хранимку и помечены как output
                                                        // но не выставляет идентификатор
                        

                        // Fetch the generated id in a separate query. This is done inside the first try/finally block
                        // to keep the insert command open, so that the batcher does not close the connection.
                        //
                        // It's possible that some ADO.NET provider will not allow two open IDbCommands for the same connection,
                        // in that case we'll have to rewrite the code to use some sort of lock on IBatcher.
                        if (!useOutputParameterForId)
                        {
                            SqlString idselectSql =
                                new SqlString(SqlIdentitySelect(IdentifierColumnNames[0], GetTableName(0)));
                            IDbCommand idselect =
                                session.Batcher.PrepareCommand(CommandType.Text, idselectSql, SqlTypeFactory.NoTypes);
                            IDataReader rs = null;

                            try
                            {
                                rs = session.Batcher.ExecuteReader(idselect);
                                return GetGeneratedIdentity(obj, session, rs);
                            }
                            finally
                            {
                                session.Batcher.CloseCommand(idselect, rs);
                            }
                        }
                        else // Получаем идентификатор
                        {
                            int paramCount = statement.Parameters.Count;
                            if (((IDbDataParameter) statement.Parameters[paramCount - 1]).Direction ==
                                ParameterDirection.Output)
                            {
                                object val = ((IDbDataParameter) statement.Parameters[paramCount - 1]).Value;
                                if (System.Convert.IsDBNull(val))
                                    return null;
                                return val;
                            }
                            else
                            {
                                return null;
                            }
                        }
                    }
                    finally
                    {
                        session.Batcher.CloseCommand(statement, null);
                    }
                }
            }
            catch (HibernateException)
            {
                // Do not call Convert on HibernateExceptions
                throw;
            }
            catch (Exception sqle)
            {
                throw Convert(sqle, "could not insert: " + MessageHelper.InfoString(this), sql.Text);
            }
        }

    public object Insert(object[] fields, object obj, ISessionImplementor session)
        {
            int span = TableSpan;
            object id;

            if (entityMetamodel.IsDynamicInsert)
            {
                // For the case of dynamic-insert="true", we need to generate the INSERT SQL
                bool[] notNull = GetPropertiesToInsert(fields);
                id = Insert(fields, notNull, GenerateInsertString(true, notNull), obj, session);
                for (int j = 1; j < span; j++)
                {
                    Insert(id, fields, notNull, j, GenerateInsertString(notNull, j), obj, session);
                }
            }
            else
            {
                // For the case of dynamic-insert="false", use the static SQL
                if (IsIdentifierAssignedByInsert)
                    id = Insert(fields, PropertyInsertability, SqlIdentityInsertString, obj, session); //вызов вышеприведенной ф-ции
                else ///if assigned by stored proc through out parameter
                {
                    //SqlCommandInfo stubCmd = new SqlCommandInfo("select null");
                    id = Insert(fields, PropertyInsertability, SqlInsertStrings[0], obj, session); //вызов вышеприведенной ф-ции
                }
                for (int j = 1; j < span; j++)
                {
                    Insert(id, fields, PropertyInsertability, j, SqlInsertStrings[j], obj, session);
                }
            }

            return id;
        }

public class IdentityGenerator : IIdentifierGenerator{...}