帮忙看看我的函数有没有合理关闭数据库连接

Question

没有
从里到外释放关闭finally
        {
            reader.Close();
            cmd.Dispose();
            myconn.Dispose();
            myconn.Close();
        }

Answer 1

public static ArrayList getReferee1()
        {
            MySqlConnection myconn = new MySqlConnection(strcon);
            myconn.Open();
            MySqlCommand cmd = new MySqlCommand("select email from referee1", myconn);
            MySqlDataReader reader = cmd.ExecuteReader();
            ArrayList al = new ArrayList();
            try
            {
                if (reader.HasRows)
                {
                    while (reader.Read())
                    {
                        al.Add(reader["email"].ToString());
                    }
                }                return al;
            }
            catch (Exception)
            {
                return null;
            }
            finally
            {
// add 
reader.Close();
                myconn.Close();
            }
        }

Answer 2

            myconn.Open();
            MySqlDataReader reader = cmd.ExecuteReader();这两句也可能产生异常，所以最好把他们try进去，而且reader最后也要关闭

Answer 3

最后都会执行finally里的语句 所以是关闭数据库了

Answer 4

dispose和close用哪个好，还是都要用？

Answer 5

MySqlDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection)只要关闭reader 就可以自动关闭连接。

Answer 6

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Answer 7

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Answer 8

我建议在创建对象时，用using(实例化对象){},他可以自动释放资源，不用手动关闭，能优化程序
代码如下：
        public static ArrayList getReferee1()
        {
            MySqlConnection myconn = new MySqlConnection(strcon);
            myconn.Open();
            MySqlCommand cmd = new MySqlCommand("select email from referee1", myconn);
            MySqlDataReader reader = cmd.ExecuteReader();
            ArrayList al = new ArrayList();
            try
            {
                if (reader.HasRows)
                {
                    while (reader.Read())
                    {
                        al.Add(reader["email"].ToString());
                    }
                }
                return al;
            }
            catch (Exception)
            {
                return null;
            }
            finally
            {
                myconn.Close();
            }
        }
public static ArrayList getReferee1()
        {
            using(MySqlConnection myconn = new MySqlConnection(strcon))
            {
                   myconn.Open();
                   MySqlCommand cmd = new MySqlCommand("select email from referee1", myconn);
                   MySqlDataReader reader = cmd.ExecuteReader();
                  ArrayList al = new ArrayList();
                  try
                 {
                         if (reader.HasRows)
                          {
                             while (reader.Read())
                            {
                                  al.Add(reader["email"].ToString());
                            }
                          }
                               return al;
                }
               catch (Exception)
              {
                return null;
              }
              finally
              {
                myconn.Close();
              }
          }
        }

Answer 9

finally
{
    if(myconn != null)//请加这个判断
    {
        myconn.Close();
    }
}