Question

我想问一下如何将多个模型对象映射到单个DTO。

我有以下EF模型如下：

Bracket.cs

namespace MyApp.Models
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Data.Entity.Spatial;

    [Table("Bracket")]
    public partial class Bracket
    {
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
        public Bracket()
        {
            Teams = new HashSet<Team>();
        }

        public int BracketId { get; set; }

        [Required]
        [StringLength(50)]
        public string BracketName { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<Team> Teams { get; set; }
    }
}

Team.cs

namespace MyApp.Models
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Data.Entity.Spatial;

    [Table("Team")]
    public partial class Team
    {
        public int TeamId { get; set; }

        [Required]
        [StringLength(50)]
        public string TeamName { get; set; }

        public int BracketId { get; set; }

        public virtual Bracket Bracket { get; set; }
    }
}

我创建了DTO对象来代表它们。

namespace MyApp.Models
{
    public class BracketDto
    {
        public int BracketId { get; set; }

        public string BracketName { get; set; }

        public List<TeamDto> Teams { get; set; }
    }

    public class TeamDto
    {
        public int TeamId { get; set; }

        public string TeamName { get; set; }

        public int BracketId { get; set; }
    }
}

在我的一个班级中，我用来查询数据库并投影结果数据，这就是我在做的事情：

public List<BracketDto> GetBrackets()
        {
            var brackets = (from a in this.Context.Brackets
                            join b in this.Context.Teams on a.BracketId equals b.BracketId
                            select new BracketDto()
                            {
                                BracketId = a.BracketId,
                                BracketName = a.BracketName
                            }).ToList<BracketDto>();

            var teams = (from a in this.Context.Teams
                         select new TeamDto()
                         {
                             TeamId = a.TeamId,
                             TeamName = a.TeamName,
                             BracketId = a.BracketId
                         }).ToList<TeamDto>();

            foreach(BracketDto bracket in brackets)
            {
                var tl = teams.Where(a => a.BracketId == bracket.BracketId).ToList();
                bracket.Teams = tl;
            }

            var xtra = (from a in this.Context.Brackets
                        join b in this.Context.Teams on a.BracketId equals b.BracketId
                        select new BracketDto()
                        {
                            BracketId = a.BracketId,
                            BracketName = a.BracketName
                        }).ToList<BracketDto>();

            return brackets;
        }

我得到的结果：

[
    {
        "BracketId": 1,
        "BracketName": "Eastern Conference",
        "Teams": [
            {
                "TeamId": 1,
                "TeamName": "Indiana Pacers",
                "BracketId": 1
            },
            {
                "TeamId": 3,
                "TeamName": "Cleveland Cavaliers",
                "BracketId": 1
            }
        ]
    },
    {
        "BracketId": 2,
        "BracketName": "Western Conference",
        "Teams": [
            {
                "TeamId": 2,
                "TeamName": "Los Angeles Lakers",
                "BracketId": 2
            },
            {
                "TeamId": 4,
                "TeamName": "Los Angeles Clippers",
                "BracketId": 2
            }
        ]
    }
]

我知道可以采用更有效的方式来做到这一点。但我不确定如何在我的LINQ查询上做到这一点。

寻找建议和意见。谢谢！

Answer 1

您拥有所有关系，您只需要利用它们。

public List<BracketDto> GetBrackets()
{
    var brackets = this.Context.Brackets.Select(a => {
        return new BracketDto(){
            BracketId = a.BracketId,
            BracketName = a.BracketName,
            Teams = a.Teams.Select(b => {
                  return new TeamDto() {
                    TeamId = b.TeamId,
                    TeamName = b.TeamName,
                    BracketId = b.BracketId
                };
            }).ToList()
        };
    }).ToList();

    return brackets;
}

实体框架将多个模型投影到单个DTO

1 个答案: