选择Linq中的子查询

Question

我的查询如下

var result = from cr in cumulativeresult
    orderby cr.Days
    select new
    {
        Days = cr.Days,
        Com = (from cr1 in cumulativeresult
            where cr1.Days < cr.Days
            group cr1 by 1 into cr1grp
            select
            new
            {
                Count = cr1grp.Count() + cr.Com 
            }),
        ComPercent = Math.Round((double.Parse((
            from cr1 in cumulativeresult
            where cr1.Days < cr.Days
            group cr1 by 1 into cr1grp 
            select cr1grp.Count() + cr.Com).ToString()) / ComCount) * 100, 2)
    };

但是,Com和ComPercent并没有成为价值观.我如何能够检索其中的值？我检索它们的循环如下

更新

foreach (var item in result)
{
    dt.Rows.Add(item.Days, item.Com, item.ComPercent);
}

我不想在我的foreach循环上做任何处理,我想在我的linq查询本身中的值.

Answer 1

编译器不知道您的子查询将始终返回一行,因为返回类型仍然是IEnumerable(或IQueryable).这可以通过使用First()或Single()(或相应的..OrDefault()版本)来解决,但是,更常见的是在Count()没有分组的情况下使用,例如:

Com = (from cr1 in cumulativeresult
       where cr1.Days < cr.Days
       select cr1
      ).Count() + cr.Com,

您可能还想考虑将子查询移动到let子句中,因此可以重用它来计算Com和ComPercent:

var result = from cr in cumulativeresult
             let totalCount = 
                      (from cr1 in cumulativeresult
                       where cr1.Days < cr.Days
                       select cr1
                      ).Count() + cr.Com 
             orderby cr.Days
             select new
             {
                Days = cr.Days,
                Com = totalCount,
                ComPercent = Math.Round((double)totalCount / ComCount * 100, 2)
             };