Question

Here is the pseudo case:

class parent{
   string name; //Some Property
   List<int> myValues;

   .......
}
........
//Initialize some parent classes

List<parent> parentList = new List<parent>();
parentList.add(parent123); //parent123.myValues == {1,2,3}
parentList.add(parent456); //parent456.myValues == {4,5,6}
parentList.add(parentMatch); //parentMatch.myValues == {1,2,3}

What I am aiming for is a query which retrieves a List of parent objects where their
myValues Lists are equivalent. In this case it would return parent123 and parentMatch.

Answer 1

So you can wrap the logic up and just use GroupBy if you implement an IEqualityComparer:

class IntegerListComparer : IEqualityComparer<List<int>>
{
    #region IEqualityComparer<List<int>> Members

    public bool Equals(List<int> x, List<int> y)
    {
        //bool xContainsY = y.All(i => x.Contains(i));
        //bool yContainsX = x.All(i => y.Contains(i));
        //return xContainsY && yContainsX;
        return x.SequenceEqual(y);
    }

    public int GetHashCode(List<int> obj)
    {
        return 0;
    }

    #endregion
}

Call it like so:

var results = list
    .GroupBy(p => p.MyValues, new IntegerListComparer())
    .Where(g => g.Count() > 1)
    .SelectMany(g => g);