C# Mongo Driver error: Cannot deserialize a 'Int32' from BsonType 'Document'

Question

以下 MongoDB 查询 运行 在 Robo3T 1.2 上很好并且 return 正确 'count'。

db.runCommand( {
aggregate: "User",
pipeline: [
{$unwind: '$UserSubscriptions'},
{$group: {
    _id: '$_id',
    codes: {$addToSet: '$UserSubscriptions.Subscription.Publication'}
}},
{$unwind: '$codes'},
{$group: {
    _id: '$codes',
    count: {$sum: 1}
}}
]
} )

我正在尝试将上述查询转换为 C# MongoDriver 查询，如下所示

 var unwind = new BsonDocument { { "$unwind", "$UserSubscriptions" } };
        var group1 = new BsonDocument
            {
                { "$group",
                    new BsonDocument
                        {
                            { "_id", new BsonDocument
                                         {
                                             {
                                                 "Id","$_id"
                                             }
                                         }
                            },
                            {
                                "codes", new BsonDocument
                                             {
                                                 {
                                                     "$addToSet","$UserSubscriptions.Subscription.Publication.Code"
                                                 }
                                             }
                            }
                        }
              }
            };
        var unwindCode = new BsonDocument { { "$unwind", "$codes" } };
        var group2 = new BsonDocument
            {
                { "$group",
                    new BsonDocument
                        {
                            { "_id", new BsonDocument
                                         {
                                             {
                                                 "Id","$codes"
                                             }
                                         }
                            },
                            {
                                "codes", new BsonDocument
                                             {
                                                 {
                                                     "$sum",1
                                                 }
                                             }
                            }
                        }
              }
            };
        var pipeline = new[] { unwind, group1 , unwindCode , group2 };
    var result = coll.Aggregate<T>(pipeline);

但是出现错误 无法从 BsonType 'Document'.

反序列化一个 'Int32'

Id 是集合中的主键

public int Id { get;放; }

请告知如何实现。

(机器人 3T 1.2.1) (MongoDB.Driver 2.4.4)

Answer 1

您正在尝试通过为“_id”创建 BsonDocument 将 BsonDocument 反序列化为 'Int32'。你只需要这样做：

var group1 = new BsonDocument
{
    { 
        "$group", new BsonDocument
        {
            { 
                "_id", "$_id"
            },
            {
                "codes", new BsonDocument
                {
                     {
                        "$addToSet", "$UserSubscriptions.Subscription.Publication.Code"
                     }
                }
            }
        }
    }
};

var group2 = new BsonDocument
{
    { 
        "$group", new BsonDocument
        {
            { 
                "_id", "$codes"
            },
            {
                "count", new BsonDocument
                {
                     {
                        "$sum", 1
                     }
                }
            }
        }
    }
};