C#中三层架构的Sqlhelper代码

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

namespace 三层架构.DAL
{
      class SqlHelper
    {
        private static readonly string connStr = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString;
        public static int ExecuteNonQuery(string cmdText, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = cmdText;
                    cmd.Parameters.AddRange(parameters);
                    return cmd.ExecuteNonQuery();
                }
            }
        }
        public static object ExecuteScalar(string cmdText, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = cmdText;
                    cmd.Parameters.AddRange(parameters);
                    return cmd.ExecuteScalar();
                }
            }
        }

        public static DataTable ExecuteDataTable(string cmdText, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = cmdText;
                    cmd.Parameters.AddRange(parameters);
                    DataTable dt = new DataTable();
                    SqlDataAdapter adapter = new SqlDataAdapter(cmd);
                    adapter.Fill(dt);
                    return dt;
                }
            }
        }
    }
}