Question

我在返回想要的字段时遇到问题。我有一个模型，我想从模型中返回特定数据。

这是我的模特。

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace api.Models
{
    [Table("ScheduleSectionRows")]
    public partial class ScheduleSectionRows
    {
        [Key]
        [Column("ScheduleRowID")]
        public int ScheduleRowId { get; set; }
        [Column("RowID")]
        public int? RowId { get; set; }
        [Column("StadiumID")]
        public int? StadiumId { get; set; }
        [Column("SectionID")]
        public int? SectionId { get; set; }
        [Column("ScheduleID")]
        public int? ScheduleId { get; set; }
        [Column(TypeName = "decimal(20, 4)")]
        public decimal? Amount { get; set; }
        public int? AvailableSeats { get; set; }
        [StringLength(50)]
        public string RowNumber { get; set; }
    }
}

基本上，我只想返回一个Json对象，该对象返回ScheduleID的标头和该ScheduleID的sectionID的列表。

这是从数据库返回样本数据

[
    {
        "ScheduleRowId": 20491,
        "RowId": 4559,
        "StadiumId": 3,
        "SectionId": 81,
        "ScheduleId": 43,
        "Amount": 100,
        "AvailableSeats": 8,
        "RowNumber": "7"
    },
    {
        "ScheduleRowId": 20492,
        "RowId": 4560,
        "StadiumId": 3,
        "SectionId": 81,
        "ScheduleId": 43,
        "Amount": 100,
        "AvailableSeats": 10,
        "RowNumber": "8"
    },
    {
        "ScheduleRowId": 20493,
        "RowId": 4561,
        "StadiumId": 3,
        "SectionId": 81,
        "ScheduleId": 43,
        "Amount": 100,
        "AvailableSeats": 10,
        "RowNumber": "9"
    },
    {
        "ScheduleRowId": 20494,
        "RowId": 4562,
        "StadiumId": 3,
        "SectionId": 81,
        "ScheduleId": 43,
        "Amount": 100,
        "AvailableSeats": 10,
        "RowNumber": "10"
    },
    {
        "ScheduleRowId": 20495,
        "RowId": 4563,
        "StadiumId": 3,
        "SectionId": 81,
        "ScheduleId": 43,
        "Amount": 100,
        "AvailableSeats": 10,
        "RowNumber": "11"
    },
    {
        "ScheduleRowId": 20496,
        "RowId": 4564,
        "StadiumId": 3,
        "SectionId": 81,
        "ScheduleId": 43,
        "Amount": 100,
        "AvailableSeats": 10,
        "RowNumber": "12"
    },
    {
        "ScheduleRowId": 20497,
        "RowId": 4565,
        "StadiumId": 3,
        "SectionId": 81,
        "ScheduleId": 43,
        "Amount": 100,
        "AvailableSeats": 5,
        "RowNumber": "13"
    },
    {
        "ScheduleRowId": 20498,
        "RowId": 4566,
        "StadiumId": 3,
        "SectionId": 81,
        "ScheduleId": 43,
        "Amount": 100,
        "AvailableSeats": 10,
        "RowNumber": "14"
    },
    {
        "ScheduleRowId": 20499,
        "RowId": 4567,
        "StadiumId": 3,
        "SectionId": 81,
        "ScheduleId": 43,
        "Amount": 100,
        "AvailableSeats": 10,
        "RowNumber": "15"
    }
]

基本上这是我想要获得的示例输出。

{
    "Status" : "Success",
    "ScheduleID" : 43,
    "SectionID": [
        {
            "SectionID" : 81,
        },
        {
            "SectionID" : 82,
        },
        {
            "SectionID" : 83,
        },
        {
            "SectionID" : 84,
        }
    ]
}

这是我的代码。

public async Task<SectionDTO<ScheduleSectionRows>> GetSection(int scheduleId)
{
    var data = _context.MlfbScheduleSectionRows
        .Where(s => s.ScheduleId == scheduleId)
        .GroupBy(
            s => s.SectionId,
            ( Section) => new { Section = Section})
        .ToListAsync();
    return new SectionDTO<MlfbScheduleSectionRows>("Success",scheduleId,data);
 }

这里是DTO。

public class SectionDTO<T> where T : class
{
    public SectionDTO(string _status,int _scheduleID, IList<T> _data)
    {
        Status = _status;
        ScheduleID = _scheduleID;
        Data = _data;
    }
    public string Status { get; set; }
    public int ScheduleID { get; set; }
    public IList<T> Data { get; set; }
}

Answer 1

首先，结果看起来需要返回唯一的SectionID。可以改写为：

var query = _context.MlfbScheduleSectionRows
    .Where(s => s.ScheduleId == scheduleId)        
    .Select(s => s.SectionId)
    .Distinct();
var data = await query.ToListAsync();

ToListAsync()本身不返回数据，而是返回一个Task，该任务将在完成后返回数据。需要await来等待该任务并获取数据。

SQL查询如下所示：

SELECT DISTINCT SectionID
FROM ScheduleSectionRows
WHERE ScheduleId = @p0

结果是一个List<int?>，它将被序列化为JSON：

[ 11, 23, 43 ]

要获得所需的结果，我们必须转换返回仅包含单个SectionID属性的类型。 LINQ的.Select()可以轻松返回匿名类型，例如data.Select(id=>new {SectionId = id})，但是我们需要一个实际的“命名”类型来传递给SectionDTO。

public class Section
{
    public int? SectionID {get;set;}
}

....

public async Task<SectionDTO<Section>> GetSection(int scheduleId)
{
    var query = _context.MlfbScheduleSectionRows
                        .Where(s => s.ScheduleId == scheduleId)        
                        .Select(s => s.SectionId)
                        .Distinct();
    var data = await query.ToListAsync();
    var sections=data.Select(id=>new Section{SectionID=id})
                     .ToList();

    return new SectionDTO<Section>("Success",scheduleId,sections);
 }

Answer 2

您必须根据您的json响应创建c＃模型，

public class SectionID
{
    public int SectionID { get; set; }
}

public class RootObject
{
    public string Status { get; set; }
    public int ScheduleID { get; set; }
    public List<SectionID> SectionID { get; set; }
}

然后您可以使用Linq .select填充此模型。

Answer 3

在将groupby与引用类型一起使用时，请确保您覆盖equals和gethashcode方法。这些用于生成分组实体的“密钥”。

在下面的代码中，我删除了where T : class上的约束SectionDTO，并使用了将键设置为int（非引用类型）的方法。它正在将值分组。

                //using Newtonsfot.Json library

                //using it to get the list data below, not required for the solution
                JArray j = JArray.Parse(GetJSONString());

                //Select the schedule id/section id as a list
                var list = j.Select(x => new { ScheduleId= Convert.ToInt32(x["ScheduleId"]) ,SectionID = Convert.ToInt32(x["SectionId"]) });

                //group by into a SectionDTO object 
                var result = list.GroupBy(x => x.ScheduleId, (key, value) => new SectionDTO<int> { Status = "Success", ScheduleID = key,  Data = value.Select(x=>x.SectionID).ToList() });

                //if you want to convert it to a json string then use the convert method
                string JSonString = JsonConvert.SerializeObject(result);

Linq .net核心中的返回特定字段

3 个答案: