C# LINQ比较2个表，只返回上一项，不返回全部

所以…每个工作站都有许多发票，我的Linq语句将工作站连接到发票，并对它们进行比较。 我只希望我的LINQ选择最近的发票（为该工作站生成的上一张发票）

ATM比较所有发票和

DateTime OneYearAgo=DateTime.Now.AddYears（-1）的任何发票（对于该工作站）；
变量选择对象=
（来自db.Work_站点中的工作站）
在db.Invoices.Where（i=>i.Invoices\u日期）中加入发票
   DateTime OneYearAgo = DateTime.Now.AddYears(-1);

        var SelectedObject =
            (from workstation in db.Work_Sites
             join invoice in db.Invoices on workstation.id equals invoice.Site_Id
              where invoice.Invoice_Date <= OneYearAgo
             select workstation).Distinct().ToList();

  DateTime OneYearAgo = DateTime.Now.AddYears(-1);

  var SelectedObject =
            (from workstation in db.Work_Sites
             join invoice in db.Invoices.Where(i => i.Invoice_Date <= OneYearAgo)
                   on workstation.id equals invoice.Site_Id into g
             where g.Any()
             select workstation).ToList();