C#封装SqlHelper

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

namespace Ytulab.DAL
{
    /// <summary>
    /// 功能：SQL数据库访问类
    /// </summary>
    public class SqlHelper
    {
        //连接字符串
        private static readonly string str = ConfigurationManager.ConnectionStrings["ytulab"].ConnectionString;
        /// <summary>
        /// 增删改
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="param">sql参数</param>
        /// <returns>受影响的函数</returns>
        public static int ExecuteNonQuery(string sql, params SqlParameter[] param)
        {
            using (SqlConnection con = new SqlConnection(str))
            {
                using (SqlCommand cmd = new SqlCommand(sql, con))
                {
                    con.Open();
                    if (param != null)
                    {
                        cmd.Parameters.AddRange(param);
                    }
                    return cmd.ExecuteNonQuery();
                }
            }
        }

        /// <summary>
        /// 查询
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="param">sql参数</param>
        /// <returns>首行首列</returns>
        public static object ExecuteScalar(string sql, params SqlParameter[] param)
        {
            using (SqlConnection con = new SqlConnection(str))
            {
                using (SqlCommand cmd = new SqlCommand(sql, con))
                {
                    con.Open();
                    if (param != null)
                    {
                        cmd.Parameters.AddRange(param);
                    }
                    return cmd.ExecuteScalar();
                }
            }
        }

        /// <summary>
        /// 多行查询
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="param">sql参数</param>
        /// <returns>SqlDataReader</returns>
        public static SqlDataReader ExecuteReader(string sql, params SqlParameter[] param)
        {
            SqlConnection con = new SqlConnection();
            using (SqlCommand cmd = new SqlCommand(sql, con))
            {
                if (param != null)
                {
                    cmd.Parameters.AddRange(param);

                }
                try
                {
                    con.Open();
                    return cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
                }
                catch (Exception ex)
                {
                    con.Close();
                    con.Dispose();
                    throw ex;
                }
            }
        }

        /// <summary>
        /// 查询多行数据
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="param">sql参数</param>
        /// <returns>一个表</returns>
        public static DataTable ExecuteTable(string sql, params SqlParameter[] param)
        {
            DataTable dt = new DataTable();
            using (SqlDataAdapter sda = new SqlDataAdapter(sql, str))
            {

                if (param != null)
                {
                    sda.SelectCommand.Parameters.AddRange(param);
                }
                sda.Fill(dt);
            }
            return dt;
        }
    
    }
}