The unclear spacing in the question doesn't help (especially around the |two|
, which has different spacing than the rest, implying we need to use trimming), but here's some custom LINQ methods that do the job. I've used the anon-type purely as a simple way of flattening out the inconsistent spacing (I could also have rebuilt a string, but it seemed unnecessary)
Note that without the odd spacing, this can be simply:
var qry = ReadLines("foo.txt")
.DistinctBy(line => line.Substring(line.IndexOf('|')));
Full code:
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
static class Program
{
static void Main()
{
var qry = (from line in ReadLines("foo.txt")
let parts = line.Split('|')
select new
{
Line = line,
Key = new
{
A = parts[1].Trim(),
B = parts[2].Trim(),
C = parts[3].Trim()
}
}).DistinctBy(row => row.Key)
.Select(row => row.Line);
foreach (var line in qry)
{
Console.WriteLine(line);
}
}
static IEnumerable<TSource> DistinctBy<TSource, TValue>(
this IEnumerable<TSource> source,
Func<TSource, TValue> selector)
{
var found = new HashSet<TValue>();
foreach (var item in source)
{
if (found.Add(selector(item))) yield return item;
}
}
static IEnumerable<string> ReadLines(string path)
{
using (var reader = File.OpenText(path))
{
string line;
while ((line = reader.ReadLine()) != null)
{
yield return line;
}
}
}
}