實體框架將多個模型投影到單個DTO

Question

我想問如何將多個模型對象映射到單個DTO。

我有以下型號EF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; } 
    } 
} 

我創建DTO對象來表示他們。

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; } 
    } 
} 

在我的課之一，我用它來查詢數據庫和項目所產生的數據，這是我在做什麼：

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; 
     } 

當我得到的結果：

[ 
    { 
     "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 
      } 
     ] 
    } 
] 

我知道可能有更有效的方法來做到這一點。但我很不確定如何在LINQ查詢中完成它。

尋找意見和建議。謝謝！

Answer 1

你擁有所有的關係，你只需要利用它們。

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; 
}