Question

我有以下对象（我在本文中使用JSON来显示我的数据）。

我需要使用LINQ C＃选择VehicleClassID = 1的年份。

** [ { “ VehicleClassID”：1 “ VehicleClassName”：“经济”， “ dbo.Vehicles”：[ { “ MakeID”：2 “ ModelID”：8 “年份”：2019 }， { “ MakeID”：6 “ ModelID”：68， “年份”：2019 }， { “ MakeID”：53 “ ModelID”：773， “年份”：2020 } ] }， { “ VehicleClassID”：2 “ VehicleClassName”：“豪华”， “ dbo.Vehicles”：[ { “ MakeID”：2 “ ModelID”：8 “年份”：2020 }， { “ MakeID”：86， “ ModelID”：1157， “年份”：2020 } ] } ] **

Answer 1

您可以使用以下查询获取车辆的所有年份

var years = data.Where(x => x.VehicleClassID == 1) //filter
                .SelectMany(x => x.Vehicles)       //select all vehicles
                .Select(x => x.Year)               //select year from each vehicle
                .ToList()                          //return list of years

Answer 2

使用Quicktype，您可以创建用于解析JSON的类：

namespace QuickType
{
    using System;
    using System.Collections.Generic;

    using System.Globalization;
    using Newtonsoft.Json;
    using Newtonsoft.Json.Converters;

    public partial class Vehicles
    {
        [JsonProperty("VehicleClassID")]
        public long VehicleClassId { get; set; }

        [JsonProperty("VehicleClassName")]
        public string VehicleClassName { get; set; }

        [JsonProperty("dbo.Vehicles")]
        public DboVehicle[] DboVehicles { get; set; }
    }

    public partial class DboVehicle
    {
        [JsonProperty("MakeID")]
        public long MakeId { get; set; }

        [JsonProperty("ModelID")]
        public long ModelId { get; set; }

        [JsonProperty("Year")]
        public long Year { get; set; }
    }

    public partial class Vehicles
    {
        public static Vehicles[] FromJson(string json) => JsonConvert.DeserializeObject<Vehicles[]>(json, QuickType.Converter.Settings);
    }

    public static class Serialize
    {
        public static string ToJson(this Vehicles[] self) => JsonConvert.SerializeObject(self, QuickType.Converter.Settings);
    }

    internal static class Converter
    {
        public static readonly JsonSerializerSettings Settings = new JsonSerializerSettings
        {
            MetadataPropertyHandling = MetadataPropertyHandling.Ignore,
            DateParseHandling = DateParseHandling.None,
            Converters =
            {
                new IsoDateTimeConverter { DateTimeStyles = DateTimeStyles.AssumeUniversal }
            },
        };
    }
}

那么您可以轻松地做到：

var vehicles = Vehicles.FromJson(jsonString);
var v = vehicles.FirstOrDefault(ve => ve.VehicleClassId == 1);
if (v != null) {
    // Your array has multiple years, so I get the first
    var year = v.DboVehicles.FirstOrDefault()?.Year ?? 0;
}

从列表中选择一个元素

2 个答案: