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

namespace DAL
{
    public class SqlHelper
    {
        //获得数据库连接字符串
        public static readonly string conString = ConfigurationManager.ConnectionStrings["sqlCon"].ConnectionString;

        /// <summary>
        /// 创建数据库连接对象
        /// </summary>
        /// <returns>返回数据库连接对象</returns>
        public static SqlConnection createCon()
        {
            return new SqlConnection(conString);
        }

        /// <summary>
        /// 创建执行对象
        /// </summary>
        /// <param name="cmdText">文本内容</param>
        /// <param name="cmdType">文本类型</param>
        /// <param name="param">可变参数数组</param>
        /// <returns>返回执行对象</returns>
        public static SqlCommand createCmd(string cmdText, CommandType cmdType, params SqlParameter[] param)
        {
            //实例化执行对象
            SqlCommand cmd = new SqlCommand();
            //执行连接对象
            cmd.Connection = createCon(); 
            //执行文本内容
            cmd.CommandText = cmdText;
            //选择文本类型
            cmd.CommandType = cmdType;

            //判断可变参数数组里是否为null 如果不为null 则添加进可变参数数组中
            if (param != null)
                foreach (SqlParameter p in param)
                    cmd.Parameters.Add(p);

            //cmd.Parameters.Clear();//执行完后清理SqlParameter中的值
            //返回执行对象
            return cmd;
        }

        /// <summary>
        /// 创建ExcuteReader()方法
        /// </summary>
        /// <param name="cmdText">文本内容</param>
        /// <param name="cmdType">文本类型</param>
        /// <param name="param">可变参数数组</param>
        /// <returns>返回读取对象</returns>
        public static SqlDataReader ExcuteReader(string cmdText, CommandType cmdType, params SqlParameter[] param)
        {
            //创建执行对象
            SqlCommand cmd = createCmd(cmdText, cmdType, param);
            try
            {
                //打开连接
                cmd.Connection.Open();
                //执行读取方法
                SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                //返回读取对象
                return dr;
            }
            catch(Exception ex)
            {
                //关闭连接
                cmd.Connection.Close();
                //返回空
                return null;
            }
        }

        /// <summary>
        /// 创建ExecuteScalar()方法
        /// </summary>
        /// <param name="cmdText">文本内容</param>
        /// <param name="cmdType">文本类型</param>
        /// <param name="param">可变参数数组</param>
        /// <returns>返回第1行第1列的值</returns>
        public static Object ExecuteScalar(string cmdText, CommandType cmdType, params SqlParameter[] param)
        {
            //创建执行对象
            SqlCommand cmd = createCmd(cmdText, cmdType, param);
            try
            {
                //打开连接
                cmd.Connection.Open();
                //执行查询方法
                Object obj = cmd.ExecuteScalar();
                //返回第1行第1列的值
                return obj;
            }
            catch(Exception EX)
            {
                //关闭连接
                cmd.Connection.Close();
                //返回空
                return null;
            }
        }

        /// <summary> 
        /// 创建ExecuteNonQuery()方法
        /// </summary>
        /// <param name="cmdText">文本内容</param>
        /// <param name="cmdType">文本类型</param>
        /// <param name="param">可变参数数组</param>
        /// <returns>返回受影响行数</returns>
        public static int ExecuteNonQuery(string cmdText, CommandType cmdType, params SqlParameter[] param)
        {
            //创建执行对象
            SqlCommand cmd = createCmd(cmdText, cmdType, param);
            try
            {
                //打开连接
                cmd.Connection.Open();
                //执行ExecuteNonQuery()方法
                int count = cmd.ExecuteNonQuery();

                //关闭连接
                cmd.Connection.Close();

                //返回受影响行数
                return count;

                
            }
            catch(Exception e)
            {
                string error = e.Message.ToString();
                //关闭连接
                cmd.Connection.Close();
                //返回 0
                return 0;
            }
        }

        /// <summary>
        /// 调用存储过程
        /// </summary>
        /// <param name="cmdText"></param>
        /// <param name="cmdType"></param>
        /// <param name="param"></param>
        /// <returns>返回DataTable类型的数据</returns>
        public static DataTable TransferProcedure(string cmdText, CommandType cmdType, params SqlParameter[] param)
        {
            //创建执行对象
            SqlCommand cmd = createCmd(cmdText, cmdType, param);
            try
            {
                //打开连接
                cmd.Connection.Open();

                SqlDataAdapter sda = new SqlDataAdapter(cmd);
                DataTable dt = new DataTable();
                sda.Fill(dt);

                //关闭连接
                cmd.Connection.Close();

                if (dt != null)
                    return dt;
                else
                    return null;

            }
            catch
            {
                //关闭连接
                cmd.Connection.Close();
                //返回 0
                return null;
            }
        }
    }
}