linq - 转换嵌套的foreach循环

Question

尝试将foreach循环转换为linq时遇到问题：

IList<DateTime> dicommentdates = new List<DateTime>();

foreach (DiaryEntry dEnt in DiaryEntries)
{
    if (dEnt.EnteredInYearGroup == this.YearGroup)
    {
        foreach (DiaryEntryComment dcom in dEnt.DiaryEntryComments)
        {
            //add all the comments for this year group
            dicommentdates.Add(dcom.DateEntered);
        }
    }
}

任何帮助都非常感激。

Answer 1

试试这个：

List<DateTime> diCommentDates = DiaryEntries.Where(dEnt => dEnt.EnteredInYearGroup == this.YearGroup)
                                            .SelectMany(dEnt => dEnt.DiaryEntryComments)
                                            .Select(dCom => dCom.DateEntered)
                                            .ToList();

Answer 2

 IList<DateTime> dicommentdates = DiaryEntries
               .Where( x=> x.EnteredInYearGroup == this.YearGroup)
               .SelectMany(x => x.DiaryEntryComments)
               .Select(x => x.DateEntered)
               .ToList()

Answer 3

这应该这样做：

IList<DateTime> dicommentdates =
    (
        from dEnt in DiaryEntries
        where dEnt.EnteredInYearGroup == this.YearGroup
        from dcom in dEnt.DiaryEntryComments
        select dcom.DateEntered
    ).ToList();

Answer 4

以下内容应该有效：

dicommentdates.AddRange(
   DiaryEntries.Where(dEnt => dEnt.EnteredInYearGroup == this.YearGroup)
   .SelectMany(dEnt => dEnt.DiaryEntryComments)).Select(dcom=> dcom.DateEntered);

Answer 5

我认为，最简单的形式是：

var dates = 
    from entry in DiaryEntries 
    where entry.YearGroup == YearGroup 
    select entry.DiaryEntryComments.DateEntered;