Remove duplicate values

Question

I have a class ClientState

Class ClientState
{
Public int ID{get;set;}
public string State{get;set;}
}

List<ClientState> listClientState which contain all states of USA, Now may problem is listClientState contain some objects which have duplicates states. How can i filter listClientState to remove duplicate record

Answer 1

You could write a comparer

class ClientStatesComparer : IEqualityComparer<ClientState>
{
    public bool Equals(ClientState x, ClientState y)
    {
        return x.State = y.State;
    }

    public int GetHashCode(ClientState obj)
    {
        return obj.State;
    }
}

and use

listClientState = listClientState.Distinct(new ClientStatesComparer()).ToList();

You will of course loose records (i.e. loose the ID) this way. If every ID is unique to a state, Veers solution will do it.

Answer 2

did you try listClientState.Distinct().ToList()

Answer 3

You could use a HashSet<>, which doesn't allow duplicates (it simply ignores them on Add()). Besides the posted answers, you can also create a HashSet from a List, and all the duplicates are ignored:

HashSet<ClientState> noDupes = new HashSet<ClientState>(listWithDupes);
List<ClientState> listNoDupes = noDupes.ToList();

Answer 4

VERY Simple example:

public class ClientState : IComparable<ClientState>
{
    public int ID { get; set; }
    public string State { get; set; }

    public override string ToString()
    {
        return String.Format("ID: {0}, State: {1}", ID, State);
    }

    #region IComparable<ClientState> Members

    public int CompareTo(ClientState other)
    {
        return other.State.CompareTo(State);
    }

    #endregion
}

static void Main(string[] args)
        {

            List<ClientState> clientStates = new List<ClientState>
                                                 {
                                                     new ClientState() {ID = 1, State = "state 1"},
                                                     new ClientState() {ID = 2, State = "state 1"},
                                                     new ClientState() {ID = 4, State = "state 3"},
                                                     new ClientState() {ID = 11, State = "state 2"},
                                                     new ClientState() {ID = 14, State = "state 1"},
                                                     new ClientState() {ID = 15, State = "state 2"},
                                                     new ClientState() {ID = 21, State = "state 1"},
                                                     new ClientState() {ID = 20, State = "state 2"},
                                                     new ClientState() {ID = 51, State = "state 1"}
                                                 };

            removeDuplicates(clientStates);
            Console.ReadLine();
        }

        private static void removeDuplicates(IList<ClientState> clientStatesWithPossibleDuplicates)
        {
            for (int i = 0; i < clientStatesWithPossibleDuplicates.Count; ++i)
            {
                for (int j = 0; j < clientStatesWithPossibleDuplicates.Count; ++j)
                {
                    if (i != j)
                    {
                        if (clientStatesWithPossibleDuplicates[i].CompareTo(clientStatesWithPossibleDuplicates[j]) == 0)
                        {
                            clientStatesWithPossibleDuplicates.RemoveAt(i);
                            i = 0;
                        }
                    }
                }
            }
        }

Output:

ID: 4, State: state 3
ID: 20, State: state 2
ID: 51, State: state 1