.netcore2.1 ef 使用外键关联查询

　
　　//实体类
  [table("invoiceinfo", schema = "obs")]
    public class invoice
    {
      
        [key]
        public string invoice_num { get; set; }

        public string merchant_id { get; set; }

        public datetimeoffset? verify_time { get; set; }

        //one to many
       public virtual ilist<invoice_relation> invoice_file_list { get; set; }

     　　//one to one
        public virtual business invoice_business { get; set; }

      
    }

//数据库  postgredbcontext相关配置

protected override void onmodelcreating(modelbuilder builder)
        {
            base.onmodelcreating(builder);
            builder.entity<invoice>().hasmany(i => i.invoice_file_list).withone().hasforeignkey(f => f.invoice_num);
            builder.entity<invoice>().hasone(i => i.invoice_business).withmany().hasforeignkey(i => i.merchant_id);
        }

 //.file为invoice_file_list类中字段属性，.invoiced_party为invoice_business字段属性
 iqueryable<invoice> invoicelist = _postgredbcontext.invoice.asnotracking().include("invoice_file_list.file").include("invoice_business.invoiced_party");