C# Mongo - Linq 按枚举过滤 -> 转换异常

Question

我尝试像这样过滤我的 mongo 集合:

    public IMongoCollection<T> GetCollection<T>()
        where T : class
    {
        return _database.GetCollection<T>(typeof(T).Name);
    }


    public IMongoQueryable<TModel> Get<TModel>() where TModel : class
    {
        return GetCollection<TModel>().AsQueryable();
    }


    public async Task<TModel> FindOneAsync<TModel>(Expression<Func<TModel, bool>> predicate) where TModel : class
    {
        var foundEntity = await Get<TModel>().FirstOrDefaultAsync(predicate);
        if (foundEntity == null)
        {
            throw new NotFoundException();
        }

        return foundEntity;
    }

然后像这样调用它:

return await Db.FindOneAsync<Node>(node => node.Type == NodeType.Start);

但 mongo 驱动程序内的枚举转换器似乎有错误。我收到以下错误:

Application startup exception: System.AggregateException: One or more errors occurred. (Convert({document}.Type, Int32) is not supported.) ---> System.InvalidOperationException: Convert({document}.Type, Int32) is not supported.

不知道我做错了什么。如果我首先将可查询的内容转换为列表，那么一切都工作正常!但随后过滤操作正在 ram 上运行。

Answer 1

似乎无法重现该错误。以下是使用最新驱动程序的情况。您的驱动程序和服务器版本是什么？

using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Driver.Linq;
using System;
using System.Linq.Expressions;
using System.Threading.Tasks;

namespace StackOverflow
{
    public class Program
    {
        public enum NodeType
        {
            Start = 1,
            End = 2
        }

        public class Node
        {
            public ObjectId Id { get; set; }
            public NodeType Type { get; set; }
        }

        private async static Task Main(string[] args)
        {
            var _database = new MongoClient("mongodb://localhost").GetDatabase("test");

            await GetCollection<Node>().InsertOneAsync(new Node { Type = NodeType.Start });

            IMongoCollection<T> GetCollection<T>() where T : class
            {
                return _database.GetCollection<T>(typeof(T).Name);
            }

            IMongoQueryable<TModel> Get<TModel>() where TModel : class
            {
                return GetCollection<TModel>().AsQueryable();
            }

            async Task<TModel> FindOneAsync<TModel>(Expression<Func<TModel, bool>> predicate) where TModel : class
            {
                var foundEntity = await Get<TModel>().FirstOrDefaultAsync(predicate);
                if (foundEntity == null)
                {
                    throw new Exception("not found");
                }
                return foundEntity;
            }

            var res = await FindOneAsync<Node>(node => node.Type == NodeType.Start);
        }
    }
}