c# - 如何在 C# 中为以下 MongoDB 查询场景编写搜索查询

Question

考虑以下 5 个参数:

1. 共同的 friend
2. 家乡
3. 当前城市
4. 学校
5. 公司

我需要编写一个搜索查询，搜索应该从匹配所有参数开始，这样才能获得准确的结果。

• 考虑至少 4 个参数
• 如果不是，则考虑至少 3 个参数
• 如果不是，则考虑至少 2 个参数
• 如果不是，则考虑至少 1 个参数
• 如果没有则显示全部。

如何在 C# 中为上述场景编写搜索查询？

我使用了下面的代码

public class UserDetails
    {
        [BsonId]
        [BsonRepresentation(BsonType.ObjectId)]
        public string _id { get; set; }
        public string UserId { get; set; }
        public Registration RegistrationDetails { get; set; }
     }
public class Registration
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }
var collection = database.GetCollection<UserDetails>("UserInfo");
                var agg = collection.Aggregate().Project(p => new
                {
                    p.Id,
                    matchValue =
                    (p.RegistrationDetails.FirstName == search ? 1 : 0) +
                    (p.RegistrationDetails.LastName == search ? 1 : 0)
                })
                .Group(new BsonDocument(new Dictionary<string, BsonValue>
                {
                    {"_id", BsonValue.Create("$matchValue")},
                    {"ids", new BsonDocument("$push", new 
                     BsonDocument("item","$Id"))}
                }))
                .Sort(new BsonDocument("_id", BsonValue.Create(-1)))
                .Limit(1)
                .Unwind("ids")
                .Project(new BsonDocument("_id", "$ids.item"));

Answer 1

使用聚合实现它的方法是:

var sr = new MongoClient("mongodb://127.0.0.1");
var db = sr.GetDatabase("Test");
var col = db.GetCollection<User>("MyUser");

var agg = col.Aggregate()
    .Project(p => new
    {
        p.Id,
        matchValue =
            (p.HomeTown == "Town 1" ? 1 : 0) +       // HomeTown condition
            (p.CurrentCity == "City 1" ? 1 : 0) +    // CurrentCity condition
            (p.School == "School 1" ? 1 : 0) +       // School condition
            (p.Company == "Company 1" ? 1 : 0)       // Company condition
        // matchValue will contains count of equal fields
    })
    .Group(new BsonDocument(new Dictionary<string, BsonValue>
    {
        {"_id", BsonValue.Create("$matchValue")},
        {"ids", new BsonDocument("$push", new BsonDocument("item","$Id")) }
        // Now I aggregate ids based on `matchValue`
    }))
    .Sort(new BsonDocument("_id", BsonValue.Create(-1)))
    .Limit(1)
    // Now I have maximum `matchValue` 
    .Unwind("ids")
    .Project(new BsonDocument("_id", "$ids.item"));
    // Now ids are available

// To gathering results I used below code:
var result = agg.ToList().Select(c=> c["_id"].AsObjectId).ToList();