C# 连接操作MYSQL 数据库_02

 using MySql.Data.MySqlclient;        // 引进MYSQL 库

 // C# 连接 MYSQL 数据库更好的方法

 void func_02()
 {
     string str_conn_info = "";
     str_conn_info += " Host       = " + db_ip + ";";
     str_conn_info += " Database   = " + db_ip + ";";
     str_conn_info += " User       = " + db_ip + ";";
     str_conn_info += " password   = " + db_ip + ";";
     str_conn_info += " port       = " + db_ip + ";";
     str_conn_info += " Charset = utf8";

     MySqlCommand sql_cmd = new MySqlCommand();
     sql_cmd.Connection = new MySqlConnection();

     sql_cmd.Connection.ConnectionString = str_conn_info;

     if (!connect_to_mysql(sql_cmd.Connection))
     {
         // 连接失败
         return;
     }

     try
     {
         // 添加SQL 语句，并运行
         sql_cmd.CommandText = "SELECT mail_id, mail_src_id, first_read_time, get_items_time, del_mail_time"
             + " FROM log_mail WHERE player_id = 1";

         // 运行的结果集放到MySqlDataReader 中
         MySqlDataReader data_reader = sql_cmd.ExecuteReader();

         // 从结果集中取数据
         try
         {
             while (data_reader.Read())
             {
                 PlayerMailRecordForm.struMailRecord mail_record = new PlayerMailRecordForm.struMailRecord();
                 mail_record.mail_id = data_reader.GetUInt32("mail_id");
                 mail_record.mail_src_id = data_reader.GetUInt32("mail_src_id");
                 mail_record.str_first_read = data_reader.GetString("first_read_time");
                 if (data_reader["get_items_time"] != DBNull.Value)    // 如果该字段 IS NOT NULL
                     mail_record.str_get_items = data_reader.GetString("get_items_time");
                 if (data_reader["del_mail_time"] != DBNull.Value)
                     mail_record.str_del_mail = data_reader.GetString("del_mail_time");
             }

             // 关闭结果集，如果不关闭，下次运行SQL 语句时会出问题。
             data_reader.Close();
         }
         catch (Exception ex)
         {
             MessageBox.Show(ex.Message);

             // 关闭结果集，如果不关闭，下次运行SQL 语句时会出问题。
             data_reader.Close();
             return;
         }
     }
     catch (System.Exception ex)
     {
         MessageBox.Show(ex.Message);
         disconnect_from_mysql(sql_cmd.Connection);
         return;
     }

     // 关闭连接
     disconnect_from_mysql(sql_cmd.Connection);

     // 这里没有找到对于MySqlCommand 释放的方法，感觉应该是没有，不过也没关系了，这里整个对象都回收了，应该是OK的。
 }

 public bool connect_to_mysql(MySqlConnection conn_clt)
 {
     switch (conn_clt.State)
     {
         case ConnectionState.Open:
         case ConnectionState.Connecting:
         case ConnectionState.Executing:
         case ConnectionState.Fetching:
         case ConnectionState.Broken:
             break;
         case ConnectionState.Closed:
         default:
             try
             {
                 conn_clt.Open();
             }
             catch(Exception ex)
             {
                 MessageBox.Show(ex.Message);
                 return false;
             }
             break;
     }

     return true;
 }

 public void disconnect_from_mysql(MySqlConnection conn_clt)
 {
     switch (conn_clt.State)
     {
         case ConnectionState.Open:
         case ConnectionState.Connecting:
         case ConnectionState.Executing:
         case ConnectionState.Fetching:
         case ConnectionState.Broken:
             conn_clt.Close();
             break;
         case ConnectionState.Closed:
         default:
             break;
     }
 }