Kris-I Kris-I - 4 months ago 23
C# Question

Get the differences between 2 lists

I have two lists (

ListA
and
ListB
), the type of these lists is the same
PersonInfo
, the
Login
field is a unique key.

public class PersonInfo
{
public string Login { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public int Age { get; set; }
public bool Active { get; set; }
}


I'd like compare these two lists :


  1. I'd like get a list of items in
    ListA
    not available in
    ListB

  2. For the items available in both lists, I'd like get a list from
    ListA
    (
    Login
    field is a unique key) for the item where there is a difference between the two lists.



Example : if for the
Login
"MyLogin" in
ListA
, the value of
FirstName
does not match with the value in
ListB
. The item with "MyLogin" as
Login
must be part of the result list.

Example : if the
Age
between
ListA
and
ListB
for a specific login is different, the item must be part of the result

Thanks.

Answer

To compare objects of custom data type lists, you will need to implement IEquatable in your class and override GetHashCode()

Check this MSDN Link

Your class

    public class PersonInfo : IEquatable<PersonInfo>
    {
        public string Login { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int Age { get; set; }
        public bool Active { get; set; }

        public bool Equals(PersonInfo other)
        {
            //Check whether the compared object is null.
            if (Object.ReferenceEquals(other, null)) return false;

            //Check whether the compared object references the same data.
            if (Object.ReferenceEquals(this, other)) return true;

            //Check whether the properties are equal.
            return Login.Equals(other.Login) && FirstName.Equals(other.FirstName) && LastName.Equals(other.LastName) && Age.Equals(other.Age) && Active.Equals(other.Active);
        }

        public override int GetHashCode()
        {

            int hashLogin = Login == null ? 0 : Login.GetHashCode();

            int hashFirstName = FirstName == null ? 0 : FirstName.GetHashCode();

            int hashLastName = LastName == null ? 0 : LastName.GetHashCode();

            int hashAge = Age.GetHashCode();

            int hashActive = Active.GetHashCode();

            //Calculate the hash code.
            return (hashLogin + hashFirstName + hashLastName) ^ (hashAge + hashActive);
        }
    }

Then here is how you use it (as listed in Pranay's response)

            List<PersonInfo> ListA = new List<PersonInfo>() { new PersonInfo { Login = "1", FirstName = "James", LastName = "Watson", Active = true, Age = 21 }, new PersonInfo { Login = "2", FirstName = "Jane", LastName = "Morrison", Active = true, Age = 25 }, new PersonInfo { Login = "3", FirstName = "Kim", LastName = "John", Active = false, Age = 33 } };
            List<PersonInfo> ListB = new List<PersonInfo>() { new PersonInfo { Login = "1", FirstName = "James2222", LastName = "Watson", Active = true, Age = 21 }, new PersonInfo { Login = "3", FirstName = "Kim", LastName = "John", Active = false, Age = 33 } };

            //Get Items in ListA that are not in ListB
            List<PersonInfo> FilteredListA = ListA.Except(ListB).ToList();

            //To get the difference between ListA and FilteredListA (items from FilteredListA will be removed from ListA)
            ListA.RemoveAll(a => FilteredListA.Contains(a));