/// <summary>
 /// 以指定连接字符串和数据库名初始化连接对象
 /// </summary>
 /// <param name="mongodbConnectionString"></param>
 /// <param name="mongodbName"></param>
 public MongoConnection(string mongodbConnectionString, string mongodbName)
 {
     if (MongoService == null)
     {
         MongoService = MongoServer.Create(mongodbConnectionString);
     }
     //MongoService.Connect();
     if (MongoDatabase == null)
     {
         if (!MongoService.DatabaseExists(mongodbName))
         {
             MongoService.CreateDatabaseSettings(mongodbName);
         }
         MongoDatabase = MongoService.GetDatabase(mongodbName);
     }
 }