compare two list and return not matching items using linq

Question

i have a two list

List SentList;
List MsgList;

both have the same property called MsgID;

MsgList            


        

Answer 1

As an extension method

public static IEnumerable AreNotEqual(this IEnumerable source, Func sourceKeySelector, IEnumerable target, Func targetKeySelector) 
{
    var targetValues = new HashSet(target.Select(targetKeySelector));

    return source.Where(sourceValue => targetValues.Contains(sourceKeySelector(sourceValue)) == false);
}

eg.

public class Customer
{
    public int CustomerId { get; set; }
}

public class OtherCustomer
{
    public int Id { get; set; }
}


var customers = new List()
{
    new Customer() { CustomerId = 1 },
    new Customer() { CustomerId = 2 }
};

var others = new List()
{
    new OtherCustomer() { Id = 2 },
    new OtherCustomer() { Id = 3 }
};

var result = customers.AreNotEqual(customer => customer.CustomerId, others, other => other.Id).ToList();

Debug.Assert(result.Count == 1);
Debug.Assert(result[0].CustomerId == 1);