Question

The below is a CSV string I am working with. Its much bigger in reality but this is enough to display a pattern.

Please note that I have put this CSV on seperate lines just to demonstrate my pattern easily.

After a CSV split the number of fields are variable depending on how big the original string is i.e. the string is a variable length which makes the number of indexes variable

The letter in the pattern may not always be P, it could be U, O or F

G9999999990001800002777107050,
G9999999990002777107HMNLAQKPRLLHRAQRWJ010,
1,
3,
29,
P,
6.74,
11.23,
07,
U,
5.25,
14.29,
08,
O,
6.89,
16.92,
07,
P,
5,
4,

I want to pick up the 5th (29) and 6th (P) elements and then miss 2 elements and then pick the next element (07) and the one after (P) and so on until I get to the end of the string.

In this example I will have
29
P
07
P
08
P
07
P

Is there an easy way to do this, I assume LINQ will offer something

Thanks

Answer 1

A full demo on http://ideone.com/EDof0

using System;
using System.Linq;
using System.Collections.Generic;

public class Program
{
    public static IEnumerable<int> SpecialIndexes()
    {
        int i=4; 

        while (i<Int32.MaxValue)
        {
            yield return i++;
            yield return i++;
            i += 2;
        }
    }

    public static void Main(string[] args)
    {
        var csvString = "G9999999990001800002777107050,G9999999990002777107HMNLAQKPRLLHRAQRWJ010,1,3,29,P,6.74,11.23,07,P,5.25,14.29,08,P,6.89,16.92,07,P,5,4,";

        var fields = csvString.Split(',');
        var selected = SpecialIndexes()
            .TakeWhile(i => i<fields.Length)
            .Select(i => fields[i]);

        Console.WriteLine(string.Join(" ", selected.ToArray()));
    }
}

Output:

29 P 07 P 08 P 07 P

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