Distinct List in c#

Question

I have a list of string[]:

List<string[]> EIndex;

Eindex list has 4 string[]

INPUT:           {0,John},{1,Mike},{2,John},{3,Tim}
Expected OUTPUT: {0,John},{1,Mike},{3,Tim}

I want to distinct the array based on index number 1 of string[] Like:

List<string[]> DistinctList = Eindex.Distinct(obj => obj[1]).ToList();

any suggestion?

'Distinct the array'? Could you give some example input and expected output? — Charles Mager, Jun 24 '15 at 13:00
Do you want to do that for the entire list, or strictly the first entry? — David W, Jun 24 '15 at 13:06

score 0 · Accepted Answer · answered Jun 24 '15 at 13:07

Distinct takes an IEqualityComparer<T> argument. You can implement a custom comparer to equate your arrays by the item at their second index:

public class SecondIndexComparer : IEqualityComparer<string[]>
{
    public bool Equals(string[] x, string[] y)
    {
        return x[1] == y[1];
    }

    public int GetHashCode(string[] obj)
    {
        return obj[1].GetHashCode();
    }
}

And use it like so:

var distinctList = Eindex.Distinct(new SecondIndexComparer()).ToList();

See a working example here: https://dotnetfiddle.net/cpv1i7

Distinct List in c#

1 Answers1