.net - Creating a distinct list of custom type in C#

Question

I receive a List of en entity framework type and want to only return the distinct values from the List. I'm using the following approach, however it's not uniquifying the list. Any suggestions?

Param: List<Flag> flags

List<Flag> distinctFlags = flags.Distinct().ToList();

The values of Flag are as follows: ID, Flag, FlagValue. Could I use linq in this instance?

Thanks.

Answer 1

Assuming Flag is one of your entity models, you could use a partial class and override Equals and GetHashCode. This also assumes that you have an Id property on on your Flag class which uniquely identities it.

//this namespace MUST match the namespace of your entity model.
namespace Your.Entity.Model.Namespace
{
    public partial class Flag
    {
        public override bool Equals(object obj)
        {
            var item = obj as Flag;

            if (item == null)
            {
                return false;
            }

            return this.Id.Equals(item.Id);
        }

        public override int GetHashCode()
        {
            return this.Id.GetHashCode();
        }
    }
}

Usage would look like this

List<Flag> distinctFlags = allFlags.Distinct().ToList();