使用 LINQ 和实体框架在一个 SQL 查询中从多个表中提取数据
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【中文标题】使用 LINQ 和实体框架在一个 SQL 查询中从多个表中提取数据【英文标题】：Pull data from multiple tables in one SQL query using LINQ and Entity Framework 【发布时间】：2020-08-10 18:18:05 【问题描述】：大家好，我正在尝试。 我需要从数据库中获取详细信息。
我参考了这个How to filter JSON array in C# 我无法做到这一点。任何人的帮助将不胜感激。
public partial class Regions
public Regions()
Projects = new HashSet<Projects>();
RegionUserRelation = new HashSet<RegionUserRelation>();
public int RegionId get; set;
[Required]
public string RegionName get; set;
[Required]
public string RegionFullname get; set;
[Required]
public int RegionTypeId get; set;
public string RegionMisc get; set;
public RegionType RegionType get; set;
public ICollection<Projects> Projects get; set;
public ICollection<RegionUserRelation> RegionUserRelation get; set;
public partial class Projects
public Projects()
Sections = new HashSet<Sections>();
public Guid ProjectId get; set;
[Required]
public string ProjectName get; set;
[Required]
public string ProjectCode get; set;
public string ProjectDesc get; set;
[Required]
public int RegionId get; set;
[Required]
public int EpsgId get; set;
public Epsg Epsg get; set;
public Regions Region get; set;
public ICollection<Sections> Sections get; set;
public partial class Sections
public Sections()
Flights = new HashSet<Flights>();
public Guid SectionId get; set;
[Required]
public string SectionName get; set;
public string SectionDesc get; set;
[Required]
public Guid ProjectId get; set;
public Projects Project get; set;
public ICollection<Flights> Flights get; set;
预期的输出是 Like
"Regions" :
[
"region_id" : "2012",
"region_name" : "region1",
"region_fullname" : "21700",
"region_type" : "MERCH",
"Projects" : [
"project_id" : 2341,
"project_name " : "DXY",
"project_code " : "21700",
"sections" : [
"section_id" : 4356,
"section_name" : sec_name,
"section_description" : sec_dis,
"section_id" : 476,
"section_name" : sec_name2,
"section_description" : sec_dis2,
"section_id" : 908,
"section_name" : sec_name3,
"section_description" : sec_dis3
]
,
"Projects" : [
"project_id" : 1321,
"project_name " : "Proj_2",
"project_code " : "01700",
"sections" : [
"section_id" : 4356,
"section_name" : sec_name,
"section_description" : sec_dis,
"section_id" : 476,
"section_name" : sec_name2,
"section_description" : sec_dis2,
"section_id" : 908,
"section_name" : sec_name3,
"section_description" : sec_dis3
]
,
]
,
"region_id" : "2013",
"region_name" : "region3",
"region_fullname" : "21330",
"region_type" : "MERCH",
"Projects" : [
"project_id" : 2341,
"project_name " : "DXY",
"project_code " : "21700",
"sections" : [
"section_id" : 4356,
"section_name" : sec_name,
"section_description" : sec_dis,
"section_id" : 476,
"section_name" : sec_name2,
"section_description" : sec_dis2,
"section_id" : 908,
"section_name" : sec_name3,
"section_description" : sec_dis3
]
,
"Projects" : [
"project_id" : 1321,
"project_name " : "Proj_2",
"project_code " : "01700",
"sections" : [
"section_id" : 4356,
"section_name" : sec_name,
"section_description" : sec_dis,
"section_id" : 476,
"section_name" : sec_name2,
"section_description" : sec_dis2,
"section_id" : 908,
"section_name" : sec_name3,
"section_description" : sec_dis3
]
,
]
,
"region_id" : "2012",
"region_name" : "region2",
"region_fullname" : "24300",
"region_type" : "MERCH",
"Projects" : [
"project_id" : 2341,
"project_name " : "DXY",
"project_code " : "21700",
"sections" : [
"section_id" : 4356,
"section_name" : sec_name,
"section_description" : sec_dis,
"section_id" : 476,
"section_name" : sec_name2,
"section_description" : sec_dis2,
"section_id" : 908,
"section_name" : sec_name3,
"section_description" : sec_dis3
]
,
"Projects" : [
"project_id" : 1321,
"project_name " : "Proj_2",
"project_code " : "01700",
"sections" : [
"section_id" : 4356,
"section_name" : sec_name,
"section_description" : sec_dis,
"section_id" : 476,
"section_name" : sec_name2,
"section_description" : sec_dis2,
"section_id" : 908,
"section_name" : sec_name3,
"section_description" : sec_dis3
]
,
]
,
]
【问题讨论】：
由于没有控制器或数据的代码，您将获得很多反对意见稍后查看此官方文档教程docs.microsoft.com/en-us/aspnet/core/tutorials/… @Pribina 是否有可能实现这一点。我检查了许多对我不起作用的教程。请帮助我摆脱困境。 应该是可以的，只要创建DTO类——在VS中你可以使用粘贴特殊Json作为类，然后crete查询映射所有属性 @Pribina 我能得到任何帮助吗.. 我对这个概念完全陌生 哪些步骤对您从数据库中检索数据或映射数据不起作用？您可以添加代码如何从数据库中检索数据吗？以及您在控制器中尝试了什么？ 【参考方案1】：根据您的 cmets 规范：使用 Include，然后使用 ThenInclude。您的模型中有导航属性，因此您可以利用它来发挥自己的优势 - 参考链接 - https://docs.microsoft.com/en-us/ef/core/querying/related-data
using (var context = new YourContex())
var regions = context.Regions
.Include(blog => blog.Projects)
.ThenInclude(post => post.Sections)
.ToList()
.Select(region => new YourDTO()); //you need to specify this by your expectation or just omit it and keep original model
【讨论】：
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