实体框架 - 一对多关系

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 tablestherefore 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;
   }

这篇关于实体框架 - 一对多关系的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！