关闭没有的DataReader
这是出错代码的类

C# code

 public  static class DBHelper    {        private static SqlConnection connection;   //private static SqlDataAdapter da;        public static SqlConnection Connection        {            get            {                string connectionString = ConfigurationManager.ConnectionStrings["XCgo"].ConnectionString;                if (connection == null)                {                    connection = new SqlConnection(connectionString);                    connection.Open();                }                else if (connection.State == System.Data.ConnectionState.Closed)                {                    connection.Open();                }                else if (connection.State == System.Data.ConnectionState.Broken)                {                    connection.Close();                    connection.Open();                }                return connection;            }        }      public static DataTable GetDataTable(string safeSql)        {            DataSet ds = new DataSet();            SqlCommand cmd = new SqlCommand(safeSql, Connection);            SqlDataAdapter da = new SqlDataAdapter(cmd);            cmd.Dispose();                da.Fill(ds);//异常出在这里，提示There is already an open DataReader associated with this Command which must be closed first.                   da.Dispose();                      connection.Close();            return ds.Tables[0];        }}

我在前台频繁点一个连接调用这个GetDataTable方法就会报一个datareader未关闭的错误,但是这个方法里没用到datareader

[解决办法]
获取datatable的底层还是使用datareader来读取的，所以会报那个错
那个错的来源是因为你把SqlConnection 定义为了static，数据层连接绝对不能这样做的
这样做意味着你的数据库一直处于一个单连接，并发的时候报错无疑