如何在Linq C＃中做到这一点

Question

So far, I have this:

var v = Directory.EnumerateFiles(_strConfigurationFolder)
    .GroupBy(x => GetReportName(Path.GetFileNameWithoutExtension(x)));

Configuration folder will contain pairs of files:

abc.json
abc-input.json
def.json
def-input.json

GetReportName() method strips off the "-input" and title cases the filename, so you end up with a grouping of:

Abc
 abc.json
 abc-input.json
Def
 def.json
 def-input.json

I have a ReportItem class that has a constructor (Name, str1, str2). I want to extend the Linq to create the ReportItems in a single statement, so really something like:

var v = Directory.EnumerateFiles(_strConfigurationFolder)
                     .GroupBy(x => GetReportName(Path.GetFileNameWithoutExtension(x)))
**.Select(x => new ReportItem(x.Key, x[0], x[1]));**

Obviously last line doesn't work because the grouping doesn't support array indexing like that. The item should be constructed as "Abc", "abc.json", "abc-input.json", etc.

Answer 1

If you know that each group of interest contains exactly two items, use First() to get the item at index 0, and Last() to get the item at index 1:

var v = Directory.EnumerateFiles(_strConfigurationFolder)
    .GroupBy(x => GetReportName(Path.GetFileNameWithoutExtension(x)))
    .Where(g => g.Count() == 2) // Make sure we have exactly two items
    .Select(x => new ReportItem(x.Key, x.First(), x.Last()));

Answer 2

var v = Directory.EnumerateFiles(_strConfigurationFolder)
                     .GroupBy(x => GetReportName(Path.GetFileNameWithoutExtension(x))).Select(x => new ReportItem(x.Key, x.FirstOrDefault(), x.Skip(1).FirstOrDefault()));

But are you sure there will be exactly two items in each group? Maybe has it sence for ReportItem to accept IEnumerable, not just two strings?