score:1

Accepted answer
dim result = lst1.selectmany(function(m) lst2.selectmany( _ 
function(c) lst3.[select](function(a) m + c + a))).tolist

dim result2 = lst1.selectmany(function(l) lst2.selectmany( _ 
function(ls) lst3.select(function(lst) string.format("{0}{1}{2}", l, ls, lst))))

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