代码大概这样
server

	[MessageHandler(AppType.Map)]
	public class C2M_GetAnnouncementList_Handler : AMRpcHandler<C2M_GetAnnouncementList, M2C_GetAnnouncementList>
	{
		protected override async ETTask Run(Session session, C2M_GetAnnouncementList request, M2C_GetAnnouncementList response, Action reply)
		{
			var dbProxy = Game.Scene.GetComponent<DBProxyComponent>();
			var infos = await dbProxy.Query<AnnouncementInfo>(_announcement => _announcement.CountNum > 0);
			response.Message = JsonHelper.ToJson(infos);
			reply();
		}
	}

客户端

            M2C_GetAnnouncementList result = (M2C_GetAnnouncementList)await SessionComponent.Instance.Session.Call(new C2M_GetAnnouncementList());

            List<AnnouncementInfo> announcementNameList = MongoHelper.FromJson<List<AnnouncementInfo>>(result.Message);

实体类
这个类型继承 ETModel.Entity

using MongoDB.Bson.Serialization.Attributes;

namespace ETModel
{
	/// <summary>
	/// 账号信息
	/// </summary>
	[BsonIgnoreExtraElements]
	public class AnnouncementInfo : Entity
	{
		//用户名
		public int CountNum { get; set; }

		//密码
		public string Filename { get; set; }
	}
}

数据传递是成功了，result.Message 没问题
但是解析的时候报错了。