最實用的DBHelper類

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
using System.Data;
using System.Configuration;

namespace GetRoomPrice
{
    public class DBHelper
    {
        /// <summary>
        /// 連接字符串
        /// </summary>
        public static readonly string ConString = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;

        /// <summary>
        /// 執行SQL語句的增刪改方法
        /// </summary>
        /// <param name="sqlText">SQL語句</param>
        /// <returns></returns>
        public static int ExecuteNonQuery(string sqlText, SqlParameter[] param)
        {
            int result = 0;
            using (SqlConnection con = new SqlConnection(ConString))
            {
                SqlCommand cmd = new SqlCommand(sqlText, con);
                if (param != null)
                    cmd.Parameters.AddRange(param);
                con.Open();
                result = cmd.ExecuteNonQuery();
            }
            return result;
        }

        public static DataTable ExecuteReader(string sqlText, SqlParameter[] param)
        {
            DataTable table = new DataTable();
            using (SqlConnection con = new SqlConnection(ConString))
            {
                SqlCommand cmd = new SqlCommand(sqlText, con);
                if (param != null)
                    cmd.Parameters.AddRange(param);

                SqlDataAdapter da = new SqlDataAdapter(cmd);
                da.Fill(table);
            }
            return table;
        }

        public static int GetIdentity(string sql, SqlParameter[] param)
        {
            object obj = null;
            using (SqlConnection con = new SqlConnection(ConString))
            {
                SqlCommand cmd = new SqlCommand(sql, con);
                if (param != null)
                    cmd.Parameters.AddRange(param);
                con.Open();
                obj = cmd.ExecuteScalar();
            }
            return obj == null ? -1 : Convert.ToInt32(obj);
        }

        public static SqlCommand CreateCommand(string commandText, SqlConnection con)
        {
            if (con.State != ConnectionState.Open)
                con.Open();
            return new SqlCommand(commandText, con);
        }
        /// <summary>
        /// 查詢返回單個值
        /// </summary>
        /// <param name="commandText"></param>
        /// <returns></returns>
        public static object ExecuteScalar(string commandText)
        {
            using (SqlConnection con = new SqlConnection(ConString))
            {
                SqlCommand cmd = CreateCommand(commandText, con);
                return cmd.ExecuteScalar();
            }

        }
    }
}