连接多个表linq

Question

下面粘贴的是一个查询，我在连接中遇到错误。

from c in Corporates.Where (a => a.EIN_NBR == "00-0000000")
join ep in EmployeePositions.Where (b => ((int)(b.EMPStartDate.Value.AddDays(28) - DateTime.Now.Date.AddDays(1)).Days) < 0)
        on c.ParentCorporateId equals ep.CorporateId
join ee in EmployeeEvaluations.Where(e => e.TargetGroupId != null) on ep.EmployeeId equals ee.EmployeeId
join ees in EmployeeEvaluationStatuses  on ee.EvaluationStatusId  equals ees.Id

join v in Vouchers.Where(b => b.SentDate == null)
on new {ep.EmployeeId, ee.Id} equals new {v.EmployeeId, v.EmployeeEvaluationId }

//在ep.EmployeeId等于v.EmployeeId && ee.Id等于v.EmployeeEvaluationId

group ep by ep.CorporateId into g
select new
{
   EmployeesMissingDocuments = g.Count()
   ,Description = "Expired"
}

我收到以下错误“无法执行文本选择：CS1941 join子句中的表达式之一的类型不正确。对'Join'的调用中类型推断失败。” 在

join v in Vouchers.Where(b => b.SentDate == null)
on new {ep.EmployeeId, ee.Id} equals new {v.EmployeeId, v.EmployeeEvaluationId }

Answer 1

您使用匿名类型来联接多个字段。 双方的匿名类型都应该相同，为此，属性名称（和类型！）应该相同。 在您的情况下，它们不是：

new {ep.EmployeeId, ee.Id} equals new {v.EmployeeId, v.EmployeeEvaluationId }

要修复，请使用相同的名称：

new {ep.EmployeeId, ee.Id} equals new {v.EmployeeId, Id = v.EmployeeEvaluationId }