对Access文件sql查询，小小程序的设计

step by step！

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.OleDb;

namespace AccessQuery
{
    class Program
    {
        static void Main(string[] args)
        {
            string database;
            Console.Write("输入Access文件的位置:");
            database = Console.ReadLine();
            OleDbDataReader reader;
            ADDO datasource = new ADDO(database);

            string sql = " ";
            while (true)
            {
                Console.WriteLine("请输入查询语句,输入q退出");
                Console.Write(">");
                sql = Console.ReadLine();

                string type = sql.Substring(0, sql.IndexOf(" ",StringComparison.CurrentCultureIgnoreCase));
                Console.WriteLine("------------------" + type + "--------------------");
                switch (type)
                {
                    case "select":
                        
                        reader = datasource.ExcuteSql(sql);
                        if (reader == null)
                            break;
                        while (reader.Read())
                        {
                            int i = 0;
                            while (i < reader.FieldCount)
                            {
                                Console.Write(reader[i].ToString());
                                i++;
                            }
                            Console.Write("\n");
                        }
                        reader.Close();
                        break;
                    case "insert":
                    case "delete":
                    case "update":
                        int count = datasource.ExcuteNoSql(sql);
                        Console.WriteLine("影响到" + count + "行");
                        break;
                    case "dbdesc":
                        string[] strtable = datasource.GetTableName();
                        if(strtable == null)
                        {
                            break;
                        }
                        foreach (string item in strtable)
                        {
                            Console.WriteLine(item);
                        }
                        break;
                    case "tabledesc":
                        Console.WriteLine("功能完善中......");
                        break;
                    case "help":
                        Console.WriteLine("dbdesc\ntabledesc\n");
                        break;
                    case "q":
                        datasource.Close();
                        Environment.Exit(0);
                        break;
                    default:
                        Console.WriteLine("你输入的语句我们的程序现在还不支持，正在完善！");
                        break;
                    
                }
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.OleDb;
using System.IO;

namespace AccessQuery
{
    class ADDO
    {
        private string connectString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=";
        private string databasePath = "";

        private OleDbConnection conn = new OleDbConnection();
        private OleDbCommand command;

        public ADDO(string database)
        {
            while (!File.Exists(database))
            {
                Console.WriteLine("文件不存在，重新输入:");
                database = Console.ReadLine();
            }

            databasePath = database;
            
            connectString += databasePath;

            conn.ConnectionString = connectString;
            try
            {
                conn.Open();
                command = new OleDbCommand("", conn);
                command.CommandTimeout = 60;
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
        }

        public void Close()
        {
            conn.Close();
        }

        public OleDbDataReader ExcuteSql(string sql)
        {
            OleDbDataReader reader;

            command.CommandText = sql;
            try
            {
                reader = command.ExecuteReader();
                return reader;
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            return null;
        }

        public int ExcuteNoSql(string sql)
        {
            command.CommandText = sql;
            try
            {
                int count = command.ExecuteNonQuery();
                return count;
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            return 0;
        }

        public string[] GetTableName()
        {
            try
            {
                DataTable shemaTable = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, new object[] { null, null, null, "TABLE" });
                int n = shemaTable.Rows.Count;
                string[] strTable = new string[n];
                int m = shemaTable.Columns.IndexOf("TABLE_NAME");

                for (int i = 0; i < n; i++)
                {
                    DataRow m_DataRow = shemaTable.Rows[i];
                    strTable[i] = m_DataRow.ItemArray.GetValue(m).ToString();
                }
                return strTable;
            }
            catch (OleDbException e)
            {
                Console.WriteLine(e.Message);
                return null;
            }
        }

        //TODO: 得到表的具体信息。
        /* 
         * 
        public DataColumn[] GetColumnInfo(string tableName)
        {
            try
            {
                if (GetTableName().Contains(tableName))
                {
                    DataTable thisTable = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables_Info, new object[] { null, null, null, "TABLE_INFO" });

                }
                else
                {
                    Console.WriteLine("输入的信息有误，请再次输入“dbdesc”，查询相关表的信息");
                    return null;
                }
            }
            catch (OleDbException e)
            {
                Console.WriteLine(e.Message);   
            }
            return null;
        }
         * */

    }
}