Generic method to compare 2 strongly typed list

Question

I have the following method that compares 2 list (of the same type) and returns the differences. How do I make this method accept lists of any type?

var differences = list1.Where(x => list2.All(x1 => x1.Name != x.Name))
            .Union(list2.Where(x => list1.All(x1 => x1.Name != x.Name)));

Answer 1

To get the difference between two sets (with order independency and multiplicity independency), you can use: HashSet<T>.SymmetricExceptWith(IEnumerable<T>) .

public static IEnumerable<T> GetSymmetricDifference<T>(IEnumerable<T> list1, IEnumerable<T> list2, IEqualityComparer<T> comparer = null)
{
    HashSet<T> result = new HashSet<T>(list1, comparer);
    result.SymmetricExceptWith(list2);
    return result;
}

In your case, to use it:

var difference = GetSymmetricDifference(list1, list2, new MyComparer());

With a custom comparer:

public class MyComparer : IEqualityComparer<MyType>
{
    public bool Equals(MyType x, MyType y)
    {
        return x.Name.Equals(y.Name);
    }

    public int GetHashCode(MyType obj)
    {
        return obj.Name == null ? 0 : obj.Name.GetHashCode();
    }
}

Answer 2

那这个呢：

var differences = list1.Except(list2).Union(list2.Except(list1));