entity-framework - Entity Framework : Assign entity to property of another entity

Question

我有这些实体(这只是我为这篇文章创建的抽象):

语言

区

说明

这些是它们之间的引用:

区 * - 1 语言

说明 * - 1 语言

区 1 - 1 说明

如果我这样取:

var myFetch = from c in context.Districts
              where c.Id = 10
              select new { DistrictId = c.Id, Lang = c.Language };

之后，我尝试将其分配给 说明 像这样:

Description desc = Description.CreateDescription(0, "My description");
desc.DistrictReference.EntityKey = new EntityKey("MyEntities.Descriptions", "DistrictId", myFetch.DistrictId);
desc.Language = myFetch.Lang; //throws error

抛出的错误是:

System.InvalidOperationException: The relationship cannot be defined because the EntitySet name 'MyEntities.Descriptions' is not valid for the role 'District' in association set name 'MyEntities.District_Description'.

我究竟做错了什么？

Answer 1

如果 myFetch是类 District 的一个实例你可以以编程方式做到这一点:

desc.DistrictReference.EntityKey = new EntityKey(  
  String.Format(  
    "{0}.{1}",   
    myFetch.EntityKey.EntityContainerName,   
    myFetch.EntityKey.EntitySetName),   
  "DistrictId", 
  myFetch.DistrictId);