打开和关闭每个查询的数据库连接

Question

我写了以下代码.我已经为一个查询打开了一次数据库连接,我想执行另一个查询.我写了下面的代码.但我认为有一个错误任何人都可以帮助我吗？

public void check()
{
    try
    {
        OdbcConnection myOdbcConnection = new OdbcConnection(con1);
        OdbcCommand myOdbcCommand = myOdbcConnection.CreateCommand();
        String sSQL = "SELECT * FROM(select tdate from tbl_IThelpdesk order by call_no desc)where ROWNUM = 1"; //last record of the call_no column
        myOdbcCommand.CommandText = sSQL;
        myOdbcConnection.Open();
        OdbcDataReader myOdbcDataReader = myOdbcCommand.ExecuteReader();
        if (!myOdbcDataReader.Read())
        {
            txtDate.Text = DateTime.Now.ToShortDateString();
            string strcallno = DateTime.Now.Year.ToString("d2") + DateTime.Now.Month.ToString("d2") + DateTime.Now.Day.ToString("d2");
            txtcall.Text = "ITHD" + strcallno + "001";
            myOdbcConnection.Close();
            myOdbcDataReader.Close();
        }
        else
        {
            DateTime today = DateTime.Parse(DateTime.Now.ToShortDateString());
            if (myOdbcDataReader[0].ToString() == today.ToString())
            {
                myOdbcConnection.Close();
                myOdbcDataReader.Close();
                myOdbcConnection.Open();
                OdbcCommand myOdbcCommand1 = myOdbcConnection.CreateCommand();
                String SQLmax = "SELECT max(call_no) FROM TBL_IThelpdesk";
                myOdbcCommand1.CommandText = SQLmax;

                OdbcDataReader myOdbcDataReader1 = myOdbcCommand1.ExecuteReader();
                while (myOdbcDataReader1.Read() != false)
                {
                    txtcall.Text = myOdbcDataReader1[0].ToString().Trim();
                }
                myOdbcDataReader1.Close();
                myOdbcDataReader.Close();
                myOdbcConnection.Close(); 
            }
        }
    }
    catch (Exception e)
    {
        lblEmpty.Text = e.Message;
        lblEmpty.Visible = true;
    }
}

Answer 1

由于数据库连接使用池,因此您不必为多个查询维护相同的连接; 相反,在需要时打开连接,并尽快关闭它以释放资源.

请参阅:http://msdn.microsoft.com/en-us/library/8xx3tyca(v = vs.80).aspx
参见:C#SQLConnection pooling

请注意,您没有使用过using() { }模式.鉴于它OdbcConnection和类似的类型实现IDisposable,你应该将它们嵌入到一个using中,以便在不等垃圾收集器的情况下处理它们.

请参阅:http://msdn.microsoft.com/en-us/library/yh598w02.aspx