顺序OleDbCommand命名参数，你了解不？

    接触到一个老的项目，里面大量使用OleDbConnection进行数据库操作，在执行SQL块语句时，对它的顺序参数、命名参数很不了解。据说不能使用命名参数，但我这里试验了一下，好像是可以的，只是对参数的顺序还是有要求。看看你能知道下面的输出结果吗？

    测试环境：OleDbConnection+Oracle10G   

using System;
using System.Data;
using System.Data.OleDb;
using System.Data.OracleClient;
using System.Text.RegularExpressions;
using System.Text;
using System.Collections;

using System.Diagnostics;
namespace ConsoleApplication1
{
    /// <summary>
    /// Class1 的摘要说明。
    /// </summary>
    class Program
    {


        private void Test1()
        {
            using(OleDbConnection conn = new OleDbConnection("Provider=OraOLEDB.Oracle;User ID=oauser;Data Source=oa163;Password=1234;Persist Security Info=True;"))
            {
                string sql = "begin  delete from B; insert into B(A,B) values(:a,:b); end;";        //很正常的

                OleDbCommand cmd = new OleDbCommand(sql,conn);

                cmd.Parameters.Add("a",OleDbType.VarChar,100);
                cmd.Parameters["a"].Value = "a";

                cmd.Parameters.Add("b",OleDbType.VarChar,100);
                cmd.Parameters["b"].Value = "b";

                cmd.CommandType = CommandType.Text;
                conn.Open();
                cmd.ExecuteNonQuery();

                cmd.CommandText = "select a,b from B";
                using(OleDbDataReader dr = cmd.ExecuteReader(CommandBehavior.SingleRow))
                {
                    Debug.Assert(dr.Read());

                    Debug.Assert(dr.GetString(dr.GetOrdinal("a")) == "a");        //正常结果
                    Debug.Assert(dr.GetString(dr.GetOrdinal("b")) == "b");
                }
                

            }
        }

        private void Test2()
        {
            using(OleDbConnection conn = new OleDbConnection("Provider=OraOLEDB.Oracle;User ID=oauser;Data Source=oa163;Password=1234;Persist Security Info=True;"))
            {
                string sql = "begin delete from B; insert into B(B,A) values(:b,:a); end;";  //这里换一下顺序 

                OleDbCommand cmd = new OleDbCommand(sql,conn);

                cmd.Parameters.Add("a",OleDbType.VarChar,100);
                cmd.Parameters["a"].Value = "a";

                cmd.Parameters.Add("b",OleDbType.VarChar,100);
                cmd.Parameters["b"].Value = "b";

                cmd.CommandType = CommandType.Text;
                conn.Open();
                cmd.ExecuteNonQuery();

                cmd.CommandText = "select a,b from B";
                using(OleDbDataReader dr = cmd.ExecuteReader(CommandBehavior.SingleRow))
                {
                    Debug.Assert(dr.Read());

                    Debug.Assert(dr.GetString(dr.GetOrdinal("a")) == "b");                //结果不一样了吧
                    Debug.Assert(dr.GetString(dr.GetOrdinal("b")) == "a");
                }
                

            }
        }

        private void Test3()
        {
            using(OleDbConnection conn = new OleDbConnection("Provider=OraOLEDB.Oracle;User ID=oauser;Data Source=oa163;Password=1234;Persist Security Info=True;"))
            {
                string sql = "declare v_exists int := 1;" +
                    "begin " +
                    "   delete from B;" +
                    "    select count(*) into v_exists from B where a=:a and b=:b and rownum < 2; " + //很正常的
                    "    if (v_exists = 0) then " +
                    "        insert into B(A,B) values(:a,:b); " +
                    "    end if; " +
                    "end;"; 

                OleDbCommand cmd = new OleDbCommand(sql,conn);

                cmd.Parameters.Add("a",OleDbType.VarChar,100);
                cmd.Parameters["a"].Value = "a";

                cmd.Parameters.Add("b",OleDbType.VarChar,100);
                cmd.Parameters["b"].Value = "b";

                cmd.CommandType = CommandType.Text;
                conn.Open();
                cmd.ExecuteNonQuery();
                
                cmd.CommandText = "select a,b from B";
                using(OleDbDataReader dr = cmd.ExecuteReader(CommandBehavior.SingleRow))
                {
                    Debug.Assert(dr.Read());

                    Debug.Assert(dr.GetString(dr.GetOrdinal("a")) == "a");                //正常结果
                    Debug.Assert(dr.GetString(dr.GetOrdinal("b")) == "b");
                }

            }

        }
        private void Test4()
        {
            using(OleDbConnection conn = new OleDbConnection("Provider=OraOLEDB.Oracle;User ID=oauser;Data Source=oa163;Password=1234;Persist Security Info=True;"))
            {
                string sql = "declare v_exists int := 1;" +
                    "begin " +
                    "   delete from B;" +
                    "    select count(*) into v_exists from B where b=:b and a=:a and rownum < 2; " +  //  b=:b and a=:a 换一下顺序
                    "    if (v_exists = 0) then " +
                    "        insert into B(A,B) values(:a,:b); " +
                    "    end if; " +
                    "end;"; 

                OleDbCommand cmd = new OleDbCommand(sql,conn);

                cmd.Parameters.Add("a",OleDbType.VarChar,100);
                cmd.Parameters["a"].Value = "a";

                cmd.Parameters.Add("b",OleDbType.VarChar,100);
                cmd.Parameters["b"].Value = "b";

                cmd.CommandType = CommandType.Text;
                conn.Open();
                cmd.ExecuteNonQuery();
                
                cmd.CommandText = "select a,b from B";
                using(OleDbDataReader dr = cmd.ExecuteReader(CommandBehavior.SingleRow))
                {
                    Debug.Assert(dr.Read());

                    Debug.Assert(dr.GetString(dr.GetOrdinal("a")) == "b");                //结果不一样了吧
                    Debug.Assert(dr.GetString(dr.GetOrdinal("b")) == "a");
                }

            }

        }

        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            //
            // TODO: 在此处添加代码以启动应用程序
            //

            try
            {
                Program prog = new Program();

                prog.Test1();
                prog.Test2();
                prog.Test3();
                prog.Test4();

            }
            catch(Exception exp)
            {
                Console.WriteLine(exp.ToString());
            }
            finally
            {
                Console.ReadLine();
            
            } 
        }
    }
}

    看起来，在OleClient中使用块语句，还是有可能的。但愿9G下不会出问题。