C#如何写DBHelper 类（数据库连接和操作）

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Data.SqlClient;

using System.Data;

using System.Configuration;

namespace UseAdo

{

    public class DBHelper

    {

    //连接字符串

      public static readonly string ConnectionString = ConfigurationManager.ConnectionStrings["SQLConn"].ToString();

//非查询操作

        public static int ExecuteNonQuery(string commandText, CommandType commandType, params SqlParameter[] param)

        {

            int count = 0;

            using (SqlConnection con = new SqlConnection(ConnectionString))

            {

                SqlCommand cmd = new SqlCommand();

                cmd.Connection = con;

                cmd.CommandText = commandText;

                cmd.CommandType = commandType;

                if (param != null)

                {

                    cmd.Parameters.AddRange(param);

                }

                con.Open();

                count = cmd.ExecuteNonQuery();

            }

            return count;

        }

//返回一个值得ExecuteScalar方法

        public static object ExecuteScalar(string commandText, CommandType commandType, params SqlParameter[] param)

        {

            object obj = null;

            using (SqlConnection con = new SqlConnection(ConnectionString))

            {

                SqlCommand cmd = new SqlCommand();

                cmd.Connection = con;

                cmd.CommandText = commandText;

                cmd.CommandType = commandType;

                if (param != null)

                {

                    cmd.Parameters.AddRange(param);

                }

                con.Open();

                obj = cmd.ExecuteScalar();

            }

            return obj;

        }

 //询方法ExecuteReader()

        public static SqlDataReader ExecuteReader(string commandText, CommandType commandType, params SqlParameter[] param)

        {

            SqlDataReader reader = null;

            SqlConnection con = new SqlConnection(ConnectionString);

            SqlCommand cmd = new SqlCommand();

            cmd.Connection = con;

            cmd.CommandText = commandText;

            cmd.CommandType = commandType;

            if (param != null)

            {

                cmd.Parameters.AddRange(param);

            }

            try

            {

                con.Open();

                //关闭reader时同时关闭connection

                reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);

            }

            catch

            {

                con.Close();

            }

            return reader;

        }

//Adapter方法

        public static DataSet ExecuteDataSet(string commandText, CommandType commandType, params SqlParameter[] param)

        {

            DataSet ds = new DataSet();

            using (SqlConnection con = new SqlConnection(ConnectionString))

            {

                SqlCommand cmd = new SqlCommand();

                cmd.Connection = con;

                cmd.CommandText = commandText;

                cmd.CommandType = commandType;

                if (param != null)

                {

                    cmd.Parameters.AddRange(param);

                }

                SqlDataAdapter adapter = new SqlDataAdapter(cmd);

                adapter.Fill(ds);

            }

            return ds;

        }

    }

}