ADO .NET 连接数据库的通用方法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.SqlClient;
namespace QQDB
{
    public class DBHelper
    {
        private string str = "Data Source=.;DataBase=QQDB;uid=sa;pwd=gaoxin";
        private SqlConnection con;
        private SqlCommand cmd;
        private SqlDataReader sdr;

        #region      //创造Connection对象
        private SqlConnection creatConnection()
        {
            con = new SqlConnection(str);
            try
            {
                if (con.State == ConnectionState.Closed)
                {
                    con.Open();
                }
                else if (con.State == ConnectionState.Broken)
                {
                    con.Close();
                    con.Open();
                }