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c# - mongo 加入嵌套集合

问题描述

我必须使用 linq 加入集合 Location 和 LocationInfo 并获得以下异常

System.NotSupportedException: '$project 或 $group 不支持 {document}。'

并尝试了以下 C# 代码

        IMongoClient client = new MongoClient();
        MongoUrl url = new MongoUrl("mongodb://localhost:27017/Database");
        MongoClientSettings settings = MongoClientSettings.FromUrl(url);
        client = new MongoClient(settings);
        IMongoDatabase database = client.GetDatabase(url.DatabaseName);

        var location = database.GetCollection<Location>("Location").AsQueryable();

        var locationInfo = database.GetCollection<LocationInfo>("LocationInfo").AsQueryable();

        var res = (from loc in locationInfo
                   from li in loc.ServiceLocation
                   join locs in location
                   on li.LocationId equals locs._id
                   select new LocationInfo
                   {
                       LocationName = loc.LocationName,
                       ServiceLocation = loc.ServiceLocation
                   });;

        var ret = res.ToList();

地点

{
"_id" : "c1828bf1-1ea0-4c48-932f-9d8ba4a19003",
"LocationNumber" : 12345
}

位置信息

{
"_id" : "35cfd485-b1eb-4724-a07d-9b0885b6fb6c",
"LocationName" : "AA Country",
"IsActive" : true,
"ServiceLocation" : [ 
    {
        "LocationId" : "c1828bf1-1ea0-4c48-932f-9d8ba4a19003",
        "Addresses" : [ 
            {
                "AddressId" : "9235bb19-cdbf-46a8-af96-cd519d081380",
                "Line1" : "xx",
                "Line2" : null,
                "City" : "xx",
                "State" : "OH",
                "IsActive" : true
            }
        ]
    }
]}

告诉我如何使用 c# Linq 来实现这个操作。

标签： c#mongodbjoin

解决方案

您可以在嵌套属性中进行查找/连接，如下所示。collection.AsQueryable()以下代码使用 MongoDB.Entities 为简洁起见，但查询与官方驱动程序的接口完全相同。

using MongoDB.Entities;
using MongoDB.Driver.Linq;
using System.Linq;

namespace StackOverflow
{
    public class Location : Entity
    {
        public string LocationNumber { get; set; }
    }

    public class LocationInfo : Entity
    {
        public string LocationName { get; set; }
        public ServiceLocation[] ServiceLocation { get; set; }
    }

    public class ServiceLocation
    {
        public string LocationId { get; set; }
        public Address[] Addresses { get; set; }
    }

    public class Address
    {
        public string AddressId { get; set; }
    }

    public class Program
    {
        private static void Main(string[] args)
        {
            new DB("Location");

            var res = 

            DB.Queryable<LocationInfo>()

              .SelectMany(li => li.ServiceLocation, //unwind the service locations
                               (li, sl) => new { locName = li.LocationName, serLoc = sl }) //project needed data in to anonymous type

              .Join(DB.Queryable<Location>(), //foregin collection
                    x => x.serLoc.LocationId, //local field in anonymous type from unwind above
                    l => l.ID,                //foreign field
                    (x, l) => new { LocationName = x.locName, ServiceLocation = x.serLoc }) //project in to final anonymous type

              .ToList();
        }
    }
}

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