CODEWITHSUNDEEP
c#linq
verygg
verygg

Reputation: 23

How to group List array in LINQ

I have an List<Array>, I'm using LINQ to find duplicates and count, but it's not work. See the image you can see, lstMyList[0] and lstMyList[11] have the same value in Int[]

Here is lstMyList definition:

List<Array> lstMyList = new List<Array>();

I used code, but it's not work:

var group = lstMyList.GroupBy(t => t).ToArray();

or

Dictionary<int[], int> count = lstMyList.GroupBy(x => x).ToDictionary(g => g.Key, g => g.Count());

Here is image: http://imageshack.com/a/img69/2552/h114.png

Maybe somebody can give me a hint about my problem.

Upvotes: 2

Views: 1360

Answers (2)

Ulugbek Umirov
Ulugbek Umirov

Reputation: 12797

First create comparer class:

sealed class ArrayEqualityComparer : IEqualityComparer<int[]>
{
    public bool Equals(int[] x, int[] y)
    {
        if (x == null && y == null)
            return true;
        if (x != null && y != null)
            return x.SequenceEqual(y);
        return false;
    }

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

Then you can use it in GroupBy clause.

List<int[]> lstMyList = new List<int[]> { new[] { 1, 2 }, new[] { 3, 4 }, new[] { 1, 2 } };
var groups = lstMyList.GroupBy(t => t, new ArrayEqualityComparer())
                      .Select(g => new { g.Key, Count = g.Count() })
                      .ToArray();

Upvotes: 3

Aron
Aron

Reputation: 15772

Try this

var group = lstMyList.GroupBy(t => t,
              StructuralComparisons.StructuralEqualityComparer).ToArray();

Upvotes: 0

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