一个用VS2010对数据库文件修改的问题
如题：通过ADO.NET技术对数据库中的数据进行更新的操作 ：

C# code

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Data.SqlClient;namespace QQManger{    class AdminTools    {         private SqlDataReader GetUserInfo()  //获取用户数据        {            try            {                StringBuilder sb = new StringBuilder();                sb.AppendLine("select UI.[UserId],UI.[UserName],L.[LevelName],UI.[Email],UI.[OnLineDay]");                sb.AppendLine("from [UserInfo] AS UI,[Level] AS L");                sb.AppendLine("where UI.[LevelId] = L.[LevelId]");                SqlCommand command = new SqlCommand(sb.ToString(), DBHelper.conn);                DBHelper.conn.Open();                return command.ExecuteReader();            }            catch (Exception ex)            {                Console.WriteLine(ex.Message);                return null;            }                    }        public string CheckLevel(int OnLineDay) //等级计算的方法        {   int level=0;            string sql = string.Format("update UserInfo set LevelId ='{0}'",level);            if (OnLineDay >= 150)            {                level = 4;            }            else if (OnLineDay >= 100 && OnLineDay < 150)            {                level = 3;            }            else if (OnLineDay >= 50 && OnLineDay < 100)            {                level = 2;            }            else            {                level = 1;            }            return sql;        }           public void UpdateUserLevel() //更新等级        {            int count = 0;            SqlDataReader reader = GetUserInfo();                            try                {                                        while (reader.Read())                    {                    int OnLineDay = Convert.ToInt32(reader["OnLineDay"]);                    string sql = CheckLevel(OnLineDay);                    SqlCommand command = new SqlCommand(sql, DBHelper.conn);                    int index = command.ExecuteNonQuery();                    if (index == 1)                    {                        count++;                    }                                    }                }                catch (Exception ex)                {                    Console.WriteLine(ex.Message);                }                finally                {                    DBHelper.conn.Close();                }           Console.WriteLine("本次一共更新"+count+"条记录");        ｝    }}

运行时提示已有打开的与此command 相关联的DataReader,必须先将其关闭。
没有发现那里打开啊。
新手求教如何修改程序

[解决办法]
public void UpdateUserLevel() //更新等级
{
int count = 0;
using(SqlDataReader reader = GetUserInfo())
{
try
{

while (reader.Read())
{
int OnLineDay = Convert.ToInt32(reader["OnLineDay"]);
string sql = CheckLevel(OnLineDay);
SqlCommand command = new SqlCommand(sql, DBHelper.conn);
int index = command.ExecuteNonQuery();
if (index == 1)
{
count++;
}

}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
DBHelper.conn.Close();
}
Console.WriteLine("本次一共更新"+count+"条记录");

}
｝
使用using吧，他会自动释放using(...)括号中创建的变量