accesshelper.cs

酒店管理 主要实现了基础设施管理（客房管理、客房类型管理）、业务管理（入住、退房、数据库切换） 本系统简单明了,适合初学者学习,采用三层加抽象工厂实现

using System;
using System.Collections.Generic;
using System.Text;

using System.Data;
using System.Data.OleDb;
using System.Configuration;

namespace DBUtility
{
    public class AccessHelper
    {
        //Database Connection strings
        public static readonly string AccessConnString = ConfigurationManager.ConnectionStrings["AccessConnectionString"].ConnectionString;
        /// <summary>
        /// Execute a OleDbCommand(that returns no resultset) against the database specified in the connection string
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.:
        /// int result = ExecuteNonQuery(connString,CommandType,StoreProcedure,"select * from RoomType",new OleDbParameter("@prodid",25))
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a OleDbConnection</param>
        /// <param name="cmdText">the CommandType(stored procedure,text,etc.)</param>
        /// <param name="type">the store procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of OleDbParameters used to execute the command</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(string connectionString, string cmdText, CommandType type, params OleDbParameter[] commandParameters)
        {
            OleDbCommand cmd = new OleDbCommand();
            using (OleDbConnection con = new OleDbConnection(connectionString))
            {
                PrepareCommand(cmd, con, null, type, cmdText, commandParameters);
                int evl = cmd.ExecuteNonQuery();
                cmd.Parameters.Clear();
                return evl;
            }
            //cmd.ExecuteReader(CommandBehavior.CloseConnection);
        }

        /// <summary>
        /// Execute a OleDbCommand that returns a resultset against the database specified in the connection string
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.:
        /// OleDbDataReader r = ExecuteReader(connString,CommandType,StoredProcedure,"select * from Room",new OleDbParameter("@Room_Number",25));
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a OleDbConnection</param>
        /// <param name="cmdType">the CommandType(stored procedure,text,etc.)</param>
        /// <param name="cmdText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of OleDbParameters used to execute the command</param>
        /// <returns>A OleDbDataReader containing the results</returns>
        public static OleDbDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText, params OleDbParameter[] commandParameters)
        {
            OleDbCommand cmd = new OleDbCommand();
            OleDbConnection conn = new OleDbConnection(connectionString);

            //we use a try/catch here because if the method throws exception we want to 
            //close the connection throw code, because no datareader will exist, hence the
            //commandBehaviour.CloseConnection will not work
            try
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                OleDbDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                cmd.Parameters.Clear();
                return rdr;
            }
            catch
            {
                conn.Close();
                throw;
            }
        }


        public static string ExecuteScalar(string connString, CommandType cmdType, string cmdText, params OleDbParameter[] cmdParameters)
        {
            string str = string.Empty;
            using (OleDbConnection conn = new OleDbConnection(connString))
            {
                OleDbCommand cmd = new OleDbCommand();
                PrepareCommand(cmd, conn, null, cmdType, cmdText, cmdParameters);
                object temp = cmd.ExecuteScalar();
                cmd.Parameters.Clear();
                str = temp as string;
            }
            return str;
        }

        /// <summary>
        /// Prepare a command for execution
        /// </summary>
        /// <param name="cmd">OleDbCommand object</param>
        /// <param name="conn">OleDbConnection object</param>
        /// <param name="trans">OleDbTransaction object</param>
        /// <param name="cmdType">CommandType e.g. stored procedure or text</param>
        /// <param name="cmdText">Command text, e.g. Select * from Products</param>
        /// <param name="cmdParms">OleDbParameters to use in the command</param>
        private static void PrepareCommand(OleDbCommand cmd, OleDbConnection conn, OleDbTransaction trans, CommandType cmdType, string cmdText, OleDbParameter[] cmdParms)
        {
            if (conn.State != ConnectionState.Open)
                conn.Open();
            cmd.Connection = conn;
            cmd.CommandText = cmdText;
            if (trans != null)
                cmd.Transaction = trans;
            cmd.CommandType = cmdType;
            if (cmdParms != null)
                foreach (OleDbParameter parm in cmdParms)
                    cmd.Parameters.Add(parm);
        }
    }
}