SELECT DISTINCT LEFT([string],2) in LINQ

Question

I need to retrieve a distinct list of the left two characters of a string.

var result = work
            .Select(w =>  w.BillCode)
            .Distinct()
            .ToList();

I've gotten a distinct list using this linq statment, but I need the distinct list of 2 digit prefixes from the BillCode.

Instead of AB1, AB2, AB3, CD1, CD2, CD3... I need just AB, CD.

This is a legacy app stuck on .Net Framework 4.7.2.

Answer 1

var result = work
    .Select(w => w.BillCode.Substring(0,2))
    .Distinct()
    .ToList();

Or, if your BillCode can have less than 2 chars:

var result = work
    .Select(w => w.BillCode.Length>2 ? w.BillCode.Substring(0,2) : w.BillCode)
    .Distinct()
    .ToList();