c# – EF 4.1一对多关系

概述我有一个非常简单的数据模型,而且我在使用EF 4.1 CF时遇到了很多困难. 我的数据模型有两个类： public class Site { public int id { get; set; } public string name { get; set; } public ICollection<Building> buildings { get; set; }}publi 我有一个非常简单的数据模型,而且我在使用EF 4.1 CF时遇到了很多困难.

我的数据模型有两个类：

public class Site {  public int ID { get; set; }  public string name { get; set; }  public ICollection<Building> buildings { get; set; }}public class Building {  public int ID { get; set; }  public int siteID { get; set; }  public string name { get; set; }}

我的配置文件是这样的：

public class SiteConfiguration : EntityTypeConfiguration<Site> {public SiteConfiguration() {  HasMany(c => c.buildings)    .Withrequired()    .HasForeignKey(c => c.siteID);  }}

在我的MVC控制器中,我只想从一个站点中删除一个建筑物.这是我的控制器代码：

public ActionResult Delete(int ID,int siteID) {  var site = repo.GetByID(siteID);  var building = site.buildings.SingleOrDefault(c => c.ID == ID);  ou.buildings.Remove(site);  repo.Save(); }

我的错误信息：

The operation Failed: The relationship
Could not be changed because one or
more of the foreign-key propertIEs is
non-nullable. When a change is made to
a relationship,the related
foreign-key property is set to a null
value. If the foreign-key does not
support null values,a new
relationship must be defined,the
foreign-key property must be assigned
another non-null value,or the
unrelated object must be deleted. Any
thoughts or suggestions would be
greatly appreciated.

解决方法 试试这个：

public class Building {    public int ID { get; set; }    public Site Site { get; set; }    ...}public class SiteConfiguration : EntityTypeConfiguration<Site> {    public SiteConfiguration()     {        HasMany(c => c.buildings);    }}public BuildingConfiguration : EntityTypeConfiguration<Building> {    public BuildingConfiguration()    {        Hasrequired(s=>s.Site);    }}

这告诉站点它可以有许多建筑物,并告诉建筑物它需要一个站点,并且不会让站点担心建立需求,反之亦然.

据我所知,你只在许多关系等中引入HasMany.WithMany / Withrequired.

总结

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