asp.net(C#)一個簡單的資料訪問類

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.Configuration;
using System.Data;
using System.Data.SqlClient;

public static class DBTool
{

    /// <summary>
    /// 建立串連
    /// </summary>
    /// <returns>SqlConnection</returns>
    public static SqlConnection GetConnection()
    {
        string connstr = ConfigurationManager.ConnectionStrings["conn"].ConnectionString;      //從設定檔中擷取連接字串

        SqlConnection conn = new SqlConnection(connstr);
        return conn;
    }

    /// <summary>
    /// 用於Select語句
    /// </summary>
    /// <param name="sql">sql語句</param>
    /// <param name="parameters">查詢參數</param>
    /// <returns>DataTable</returns>
    public static DataTable GetDataTable(string sql, params  SqlParameter[] parameters)
    {
        DataTable dt = new DataTable();
        SqlConnection conn = GetConnection();

        SqlCommand cmd = new SqlCommand(sql, conn);

        cmd.Parameters.AddRange(parameters);
        SqlDataAdapter da = new SqlDataAdapter(cmd);

        da.Fill(dt);       //為dt填充資料

        return dt;
    }

    //一個可以用於非Select語句的方法，主要用於insert,delete,update語句
    /// <summary>
    /// 用於Update，Insert，Delete語句
    /// </summary>
    /// <param name="sql">sql語句</param>
    /// <param name="parameters">查詢參數</param>
    /// <returns>Int32</returns>
    public static int ExecuteNonQuery(string sql, params SqlParameter[] parameters)
    {
        int i = 0;
        using (SqlConnection conn = GetConnection())
        {
            SqlCommand cmd = new SqlCommand(sql, conn);
            cmd.Parameters.AddRange(parameters);

            conn.Open();

            i = cmd.ExecuteNonQuery();

        }
        return i;
    }

    /// <summary>
    /// 讀取資料流中的資訊
    /// </summary>
    /// <param name="sql">sql語句</param>
    /// <param name="parameters">查詢參數</param>
    /// <returns>SqlDataReader</returns>
    public static SqlDataReader ExecuteReader( string sql, params SqlParameter[] parameters)
    {
        SqlConnection conn = GetConnection();

        SqlCommand cmd = conn.CreateCommand();
        cmd.CommandText = sql;

        foreach (SqlParameter p in parameters)
        {
            cmd.Parameters.Add(p);
        }

        conn.Open();

        SqlDataReader sdr = cmd.ExecuteReader();       //select,  返回結果集

        return sdr;
    }
}