In LINQ how to check all fields of a inner list in a list with all fields of a inner list in another list?

Question

This is my model:

class A
{
    public string Value { get; set; }
    public int? bId { get; set; }
    public B b { get; set; }
}
class B
{
    public int Id { get; set; }
    public List<A> aList { get; set; }
    public B ()
    {
        aList = new List<A>();
    }
}

Now in my program I have two objects of b and want to compare both lists of a in the b type.

I have two lists of b:

bool checkingDuplicatedObjects(List<B> b1, List<B> b2)
{
    List<B> q = new List<B>();
    if (b1.Count != b2.Count)
        return false;
    for (var i = 0; i < b1.Count; i++)
    {
        var x = b1[i];
        var y = b2[i];
        q = (from n1 in x.aList
             from n2 in y.aList
             where n1.Value == n2.Value
             select x).ToList();
    }
    if (q.Count() > 0)
        return true;
    else
        return false;
}

But I think this code is not completely logical. Can you please help me?

Answer 1

Ok there are many ways of doing this

    bool CheckDup(List<B> b1, List<B> b2)
    {

        if (b1.Count != b2.Count)
        {
            return false;
        }

        for (int i = 0; i < b1.Count; i++)
        {
            B x = b1[i];
            B y = b2[i];

            var c = x.aList.Select(al => al.Value).ToList();
            var d = y.aList.Select(al => al.Value).ToList();

            bool isEqual = c.SequenceEqual(d);

            if (!isEqual)
            {
                return false;
            }
        }

        return true;
    }

But we can make this look better by adding IEqualityComparer<> to A

class A: IEqualityComparer<A>
{
    public string Value { get; set; }
    public int? bId { get; set; }
    public B b { get; set; }

    public bool Equals(A? a1, A? a2)
    {
        return a1?.Value == a2?.Value;
    }

    public int GetHashCode(A a)
    {
        throw new NotImplementedException();
    }
}

With the Method now looking like this

    bool CheckDup(List<B> b1, List<B> b2)
    {

        if (b1.Count != b2.Count)
        {
            return false;
        }

        for (int i = 0; i < b1.Count; i++)
        {
            B x = b1[i];
            B y = b2[i];

            bool isEqual = x.aList.SequenceEqual(y.aList);

            if (!isEqual)
            {
                return false;
            }
        }

        return true;
    }

Or we can go really wild and also add the interface to B

class B : IEqualityComparer<B>
{
    public int Id { get; set; }
    public List<A> aList { get; set; }
    public B()
    {
        aList = new List<A>();
    }


    public bool Equals(B? b1, B? b2)
    {
        return b1.aList.SequenceEqual(b2.aList);
    }
    public int GetHashCode(B b)
    {
        throw new NotImplementedException();
    }
}

With this further shortening the Method to this

bool CheckDup(List<B> b1, List<B> b2)
{

    if (b1.Count != b2.Count)
    {
        return false;
    }


    bool eq = b1.SequenceEqual(b2);

    return eq;
}

Now be mindful that SquenceEquals is also dependent on the order. So List [1 2 3] and [1 2 3] are the same but [1 2 3] and [2 1 3] are not. If you wanna ignore order then you would need to change some things.

The first example would need to be changed to

    bool CheckDup(List<B> b1, List<B> b2)
    {

        if (b1.Count != b2.Count)
        {
            return false;
        }

        for (int i = 0; i < b1.Count; i++)
        {
            B x = b1[i];
            B y = b2[i];

            var c = x.aList.Select(al => al.Value).ToList();
            var d = y.aList.Select(al => al.Value).ToList();

            bool isEqual = c.All(d.Contains);

            if (!isEqual)
            {
                return false;
            }
        }

        return true;
    }

The Second to

    bool CheckDup(List<B> b1, List<B> b2)
    {

        if (b1.Count != b2.Count)
        {
            return false;
        }

        for (int i = 0; i < b1.Count; i++)
        {
            B x = b1[i];
            B y = b2[i];

            bool isEqual = x.aList.All(y.aList.Contains) && x.aList.Count == y.aList.Count;

            if (!isEqual)
            {
                return false;
            }
        }

        return true;
    }

And in the third we would need to change Bs Equals Method to

public bool Equals(B? b1, B? b2)
{
    return b1.aList.All(b2.aList.Contains) && b1.aList.Count == b2.aList.Count;
}