Why do you need to use LINQ? The following code solves it without LINQ overhead:
var val = line.Split('\t')[indexToGet];
: , , , . , LINQ ElementAt. , .ToArray().GetValue(indexToGet).ToString(); :
var val =
(from str in line.Split('\t')
select str).ElementAt(indexToGet);
, , , ( ), :
var val = line.Split('\t').ElementAt(indexToGet);
, ElementAt , :
var val = line.Split('\t')[indexToGet];