实体框架 - 一对多关系 [英] EntityFramework - One to many relationship

问题描述

我在MapHeader和MapDetail表
之间有一对多的关系，因此，单个地图头可以有多个mapdetails。
在数据库中，表 MapDetail 具有外键MapHeaderID，它映射到 MapHeader 表中的pk（MapHeaderId）。

I have a one-to-many relationship between MapHeader and MapDetail tables therefore there can be multiple mapdetails for a single mapheader. In the database, table MapDetail has foreign key MapHeaderID which maps to the pk(MapHeaderId) in MapHeader table.

我已经在EntityFramework Code-first中定义了它，如下所示：

I have defined it in EntityFramework Code-first as follows:

public class MapHeader
{
    public int MapHeaderID { get; set; }
    ....
    public virtual ICollection<MapDetail> mapDetails
    {
        get;
        set;
    } 
 }

public class MapDetail
{
    public int MapDetailID { get; set; }
    public int MapHeaderID { get; set; }
    ....
    public virtual MapHeader mapheader { get; set; }
}

FLUNETAPI

modelBuilder.Entity<MapDetail>()
            .HasRequired<MapHeader>(md => md.mapheader)
            .WithMany(mh => mh.mapDetails)
            .HasForeignKey(md => md.MapHeaderID);

它不链接！ mapDetail中的mapheader属性仍然为null ...我做错了什么？

It does not link!! my mapheader property inside mapdetail record/object is still null...What am i doing wrong?

代码 - 在RAZOR VIEW中写入

foreach (MapDetail geMapDetail in Model.mapDetails)
   {
     if(...)
     {
       if(...){...}
       else{
          <td>
          foreach(..)
          {
              var term = geMapDetail.Term == 0 ? geMapDetail.mapheader.Term : geMapDetail.Term;
          }
          </td>
       }
     }

代码崩溃上面的geMapDetail.mapheader，因为mapheader是null

the code crashes on the above geMapDetail.mapheader since mapheader is null

我的查询是存储过程

select distinct md.yearid, md.assessmentid, md.resulttypeid,
    concat(ah.name, ' - ', a.name) as Name, md.term, md.semester, md.month, md.week,
   md.MapDetailID, md.MapHeaderID, md.ColourFormatType, md.ResultTypeIDs,
    md.RowOrder, md.Attendance, md.EffectSize, md.Growth, md.IndicatorID,
    md.TeacherNameRequired, md.AllowEdit, md.PageHeaderID, md.IncludePreviousTerms,
    md.IncludePreviousSemesters, y.year
from mapdetail md
left outer join assessments a on a.assessmentid = md.assessmentid
left outer join assessments ah on ah.assessmentID = a.headerID
left outer join years y on md.yearID = y.yearID
left outer join assessmentresulttypes art on a.assessmentid = art.assessmentid
left outer join resulttypes rt on rt.resulttypeid = art.resulttypeid
where  md.mapheaderid = 22;

DBCONTEXT

 public MapDetailResultSet Find_MapDetails(int mapHeaderId, int yearId, string classIds, int indicatorGroup, string indicatorIds)
    {
        var query = "CALL Find_MapDetails(@mapHeaderId, @yearId, @classIds, @indicatorGroup, @indicatorIds)";

        MySqlParameter[] mySqlParams = new MySqlParameter[] { new MySqlParameter("mapHeaderId", mapHeaderId),
                                                                new MySqlParameter("yearId", yearId),
                                                                new MySqlParameter("classIds", classIds),
                                                                new MySqlParameter("indicatorGroup", indicatorGroup),
                                                                new MySqlParameter("indicatorIds", indicatorIds)
                                                            };

        MapDetailResultSet mapdetails = new MapDetailResultSet();

        using (var multiResultSet = DbContextExtensions.MultiResultSetSqlQuery(this, query, mySqlParams))
        {
            mapdetails.mapDetails = multiResultSet.ResultSetFor<MapDetail>().ToList();
            //other result sets
            ...

        }
  return mapdetails;
  }

我还在DBContext中禁用了lazyloading：（did not help）

I have also disabled lazyloading in DBContext: (didnt help)

 public geContext(string connString):base(connString) 
    {
        this.Configuration.LazyLoadingEnabled = false;
        Database.SetInitializer(new MySqlInitializer());
    }

更新

select distinct md.yearid, md.assessmentid, md.resulttypeid,
    concat(ah.name, ' - ', a.name) as Name, md.term, md.semester, md.month, md.week,
   md.MapDetailID, md.MapHeaderID, md.ColourFormatType, md.ResultTypeIDs,
    md.RowOrder, md.Attendance, md.EffectSize, md.Growth, md.IndicatorID,
    md.TeacherNameRequired, md.AllowEdit, md.PageHeaderID, 
    md.IncludePreviousTerms,
    md.IncludePreviousSemesters, y.year
   from mapdetail md
   left outer join assessments a on a.assessmentid = md.assessmentid
   left outer join assessments ah on ah.assessmentID = a.headerID
   left outer join years y on md.yearID = y.yearID
   left outer join assessmentresulttypes art on a.assessmentid = art.assessmentid
   left outer join resulttypes rt on rt.resulttypeid = art.resulttypeid
   left outer join mapheader mh on mh.mapheaderID = md.mapheaderID
    where  md.mapheaderid = 22;

推荐答案

不是理想的做法，无论如何，
i从存储库中加载特定的地图头，然后手动填充列表中的每个mapdetail对象。

not the ideal way to do but it got me through anyway.. i loaded the particular mapheader from the repository and then populated each mapdetail object in the list manually

控制器

   MapHeaderRepository repMapHeader = new MapHeaderRepository("name=ge");
   MapDetailsRepository repMapDetail = new MapDetailsRepository("name=ge");

   MapDetailResultSet mapDetailResultSet = repMapDetail.FindMapDetails(mapHeaderId, yearId, classIds, 
                                                    indicatorGroup, indicatorIds);
   var mapHeader = repMapHeader.Get(22);

   foreach (MapDetail md in mapDetailResultSet.mapDetails)
   {
        md.mapheader = mapHeader;
   }

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