How to filter String array with integer array with LINQ by index?

Question

String[] columnList = new String[]{"column1","column2","column3","column4","column5","column6","column7","column8","column9","column10","column11","column12" };

Int[] fList = new Int[] { 1,3,5,10,12 };

I want output like this:

column1,column3,column5,column10,column12

This question might help you. It is a bit different, but should be similar other than some string formatting: https://stackoverflow.com/questions/728319/linq-orderby-against-specific-values — bisen2, Nov 28 '20 at 16:17
This sounds like homework. You sould at least shown an attempt. — JHBonarius, Nov 28 '20 at 16:18

score 2 · Answer 1 · answered Nov 28 '20 at 16:18

2

You can combine String.Join with Select

string result = string.Join(",", fList.Select(n => columnList[n-1]));

Obviously you need to ensure that the index exists. If you dont know that you could use ElementAtOrDefault(n-1) instead of [n-1].

answered Nov 28 '20 at 16:18

Tim Schmelter

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This method works. Thanks a Lot. 2 hours struggle. – Sund'er Nov 28 '20 at 16:35

score -1 · Accepted Answer · answered Nov 28 '20 at 16:26

I hope this is not homework! This will do the trick:

var joined = from column in columnList.Select((x, i) => new {Index = i + 1, Column = x} )
             join index in fList on column.Index equals index
             select column.Column;
Console.WriteLine(string.Join(",", joined));

// output
// column1,column3,column5,column10,column12

How to filter String array with integer array with LINQ by index?

2 Answers2