WinForm程序中使用 .net MySql 连接器，主窗体未关闭时， MySql 连接没有释放。

using (MySqlConnection conn = new MySqlConnection(connectionString))
            {
                conn.Open();
                MySqlCommand cmd = new MySqlCommand();
                cmd.Connection = conn;               
                try
                {
                                     
                }
                catch (Exception ex)
                {
                    return 0;
                }
                finally
                {
                    if (conn.State == ConnectionState.Open)
                    {
                        conn.Close();
                        MySqlConnection.ClearPool(conn);//加入此行可释放连接
                        conn.Dispose();                       
                    }
                    GC.Collect();
                }
            }

上述代码在执行close后，通过SHOW STATUS LIKE 'Threads%'查看，当前连接数未发生变化，退出整个程序后，连接才释放。

所以，在close后，还要执行MySqlConnection.ClearPool(conn)，才可以释放连接。