如何使用最新的 MongoDB C# 驱动程序根据多个条件删除复杂数组对象的嵌套数组中的元素？

Question

总体目标是能够根据用户标识和进餐标识来查找餐点。 如果找到该项目，我希望能够仅删除与 userid 和 mealid 匹配的整个元素。

Currently, After sending the request object via postman in a post request, I have tried to write a variation of queries using the C# to create a builder object, and then filter to find the specific array object, and finally delete the array object if there是userid 和 mealid的匹配项。 最初，我遇到的问题是整个元素没有被删除，但只有嵌套在元素内部的内部数组元素被（没有删除，但设置回 null 值）。 但是，现在的问题是整个数组元素根本没有被删除，我收到以下错误。 Visual Studio 中的 BsonArraySerializer 错误

有人可以帮我解决这个问题吗？

这是我通过 postman 发送的示例 object，我试图删除它：示例 Postman POST 请求与正文数据

这是我要删除的数据示例图像： Json Array Elemet 的示例图像我要删除

You will need MongoDb Compass or Atlas, .NET Core 3.1, MongoDB C# Driver 2.0, Postman, and .NET Core 3.1 WebApi Project/Solution in order to help solve this issue.

下面是复制问题所需的代码：

启动.cs

将这行代码添加到该文件的Configuration方法中

services.AddScoped<IMealsRepository, MealsRepository>();

将此行添加到 ConfigureServices 方法

services.AddSingleton(sp =>
            sp.GetRequiredService<IOptions<DatabaseSettings>>().Value);

appSettings.json

将这些代码行添加到此文件中

 "DatabaseSettings": {

    "ConnectionString": "your connection string to MongoDb"

}

数据库设置.cs

    public class DatabaseSettings
    {
        public string ConnectionString { get; set; } 
    }

MealPlanModel.cs:

using MongoDB.Bson;

using MongoDB.Bson.Serialization.Attributes;

public class MealPlanModel
{

    #region MealPlanModel fields
    [BsonElement("userid")]
    public int? UserId { get; set; }

    [BsonElement("mealid")]
    public int? MealId { get; set; }

    [BsonElement("mealname")]
    public string MealName { get; set; }

    [BsonElement("mealimage")]
    public string MealImage { get; set; }

    [BsonElement("foods")]
    public FoodModel[] Foods { get; set; }

    [BsonElement("totalcalories")]
    public double TotalCalories { get; set; }

    [BsonElement("totalprotein")]
    public double TotalProtein { get; set; }

    [BsonElement("totalcarbs")]
    public double TotalCarbs { get; set; }


    [BsonElement("totalfat")]
    public double TotalFat { get; set; }

    [BsonElement("totalsugar")]
    public double TotalSugar { get; set; }

    [BsonElement("totalfiber")]
    public double TotalFiber { get;  set; }
    #endregion

    #region MealPlanModel ctor
    public MealPlanModel()
    {

    }

    public MealPlanModel(int userid, int mealid)
    {
        UserId = userid;
        MealId = mealid;
    }
}

MealPlanDto.cs

using MongoDB.Bson;

using MongoDB.Bson.Serialization.Attributes;

using System.Collections.Generic;

public class MealPlanDto

{

    [BsonId]
    public ObjectId Id { get; set; }

    [BsonElement("meals")]
    public List<MealPlanModel> MealPlans { get; set; }
}

**MealsController.cs:**


using System;

using System.Collections.Generic;

using System.IO;

using System.Linq;

using System.Security.Claims;

using System.Threading.Tasks;

using AutoMapper;

using Microsoft.AspNetCore.Authorization;

using Microsoft.AspNetCore.Http;

using Microsoft.AspNetCore.Mvc;

using Newtonsoft.Json;

[Route("api/[controller]")]

[ApiController]

public class MealsController : ControllerBase

{


    private readonly IMealsRepository _repo;

    private readonly IMapper _mapper;

    public MealsController(IMealsRepository repo, IMapper mapper)
    {
        _repo = repo;

        _mapper = mapper;

    } 


    [HttpGet, Route("CheckConnection")]

    public async Task<IActionResult> CheckConnection()

    {

        var result = await _repo.CheckConnection();

        if (result == null || result.Count <= 0)

            return BadRequest("Failed to connect to database.");

        return Ok("Database connection was successful");

    }

    [HttpPost("deletecustommeal")]

    public async Task<IActionResult> DeleteCustomMealPlan(int id)

    {

      var requestBody = await new StreamReader(HttpContext.Request.Body).ReadToEndAsync();
      var mealPlanToDelete = JsonConvert.DeserializeObject<MealPlanModel>(requestBody);
      MealPlanDto deleteMealPlan = new MealPlanDto();
      deleteMealPlan.MealPlans = new List<MealPlanModel>();
      deleteMealPlan.MealPlans.Add(mealPlanToDelete);
      var result = await _repo.DeleteCustomMealPlanById(deleteMealPlan);
      if (!result)
         return BadRequest("Failed to delete meal");
      return Ok("Successfully deleted meal plan");
    }

}

MealsRepository.cs

using Microsoft.Extensions.Configuration;

using MongoDB.Bson;

using MongoDB.Driver;

using System;

using System.Collections.Generic;

using System.Threading.Tasks;

public class MealsRepository : IMealsRepository

{

    private readonly MongoClient _client;

    private readonly IMongoDatabase _database;

    private readonly IMongoCollection<MealPlanDto> _userMealsCollection;

    public MealsRepository(IConfiguration configuration)
    {
        _client = new 
          MongoClient(configuration.GetSection("DatabaseSettings").GetSection("ConnectionString").Value);
        _database = _client.GetDatabase("MealsDb");
        _userMealsCollection = _database.GetCollection<MealPlanDto>("meal");
    }

    public async Task<List<BsonDocument>> CheckConnection()
    {
        List<BsonDocument> list = await _database.ListCollections().ToListAsync();
        var populatedList = (list != null && list.Count > 0) ? list : null;
        return populatedList;
    }

    public async Task<bool> DeleteCustomMealPlanById(MealPlanDto mealPlanToDelete)

    {
        var builder = Builders<MealPlanDto>.Filter;
        var filter = builder.Eq(x => x.MealPlans[0].UserId, mealPlanToDelete.MealPlans[0].UserId);

        var update = Builders<MealPlanDto>.Update.PullFilter(
            p => (IEnumerable<MealPlanModel>)p.MealPlans[0],
            f => f.MealId.Value == mealPlanToDelete.MealPlans[0].MealId);

        try
        {
            await _userMealsCollection.UpdateOneAsync(filter, update);
            return true;
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Failed to delete meal plan. {ex} occured.");
            return false;
        }
    }

}

Answer 1

感谢所有试图找到上述问题的答案的人，但我实际上发现了一个简单的解决方案

我只是用以下内容替换了 Repository.cs 文件中的上述方法，它就像一个魅力

public bool DeleteCustomMealPlanForUserById(MealPlanModel mealPlanToDelete)
    {
        var result = _customUserMealsCollection.DeleteOne(p => p.MealPlans[0].UserId == mealPlanToDelete.UserId
            && p.MealPlans[0].MealId == mealPlanToDelete.MealId);

        return result.DeletedCount != 0;
    }