Linq使用Include加载关联属性时如何同时加载Contact的Role与Company属性

解决方案 #

你只需要额外添加一条关联加载链指定加载Contact下的Company属性即可，EF Core支持同时声明多个关联加载路径，所有显式指定的导航属性都会被正确加载。

写法1：兼容所有EF Core版本

query = db.Persons.Include(entity => entity.ContactRelations)
                .ThenInclude(relation => relation.Contact)
                .ThenInclude(contact => contact.Role)
           .Include(entity => entity.ContactRelations)
                .ThenInclude(relation => relation.Contact)
                .ThenInclude(contact => contact.Company);

写法2：EF Core 5.0及以上版本支持的简化写法

EF Core 5.0 新增了同层级导航属性并行加载的语法，不需要重复写上层关联路径：

query = db.Persons.Include(entity => entity.ContactRelations)
                .ThenInclude(relation => relation.Contact)
                    .Include(contact => contact.Role)
                    .Include(contact => contact.Company);

内容的提问来源于stack exchange，提问作者Luka