sqlhelper.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.SqlClient;
using System.Data;
using System.Configuration;
//５1ａspｘ

namespace DBUtility
{
    public abstract class SQLHelper
    {
        //Database Connection strings
        public static readonly string SQLConnString = ConfigurationManager.ConnectionStrings["SQLServerConnectionString"].ConnectionString;
        /// <summary>
        /// Execute a SqlCommand(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 SqlParameter("@prodid",25))
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</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 SqlParameters 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 SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                PrepareCommand(cmd, con, null, type, cmdText, commandParameters);
                int evl = cmd.ExecuteNonQuery();
                cmd.Parameters.Clear();
                return evl;
            }
            //cmd.ExecuteReader(CommandBehavior.CloseConnection);
        }

        /// <summary>
        /// Execute a SqlCommand that returns a resultset against the database specified in the connection string
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.:
        /// SqlDataReader r = ExecuteReader(connString,CommandType,StoredProcedure,"select * from Room",new SqlParameter("@Room_Number",25));
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</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 SqlParameters used to execute the command</param>
        /// <returns>A SqlDataReader containing the results</returns>
        public static SqlDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            SqlConnection conn = new SqlConnection(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);
                SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                cmd.Parameters.Clear();
                return rdr;
            }
            catch
            {
                conn.Close();
                throw;
            }
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="connString"></param>
        /// <param name="cmdType"></param>
        /// <param name="cmdText"></param>
        /// <param name="cmdParameters"></param>
        /// <returns></returns>
        public static string ExecuteScalar(string connString, CommandType cmdType, string cmdText, params SqlParameter[] cmdParameters)
        {
            string str = string.Empty;
            using (SqlConnection conn = new SqlConnection(connString))
            {
                SqlCommand cmd = new SqlCommand();
                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">SqlCommand object</param>
        /// <param name="conn">SqlConnection object</param>
        /// <param name="trans">SqlTransaction 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">SqlParameters to use in the command</param>
        private static void PrepareCommand(SqlCommand cmd,SqlConnection conn, SqlTransaction trans, CommandType cmdType, string cmdText, SqlParameter[] 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 (SqlParameter parm in cmdParms)
                    cmd.Parameters.Add(parm);
        }
    }
}