Get distinct items by combination from list C#

Question

My object like like this

    public class Region
{
    public Region();

    public string City { get; set; }
    public int PostCode { get; set; }
    public string WfRegion { get; set; }
}

I have a list of this objects in this class Where data is like this

Rodney , 7845 , Auckland
Rodney , 3435 , Auckland
Rodney , 4566 , Auckland
Rodney , 3445 , North Island

I want to filter this list so that I can get an output like this

    Rodney , 7845 , Auckland
    Rodney , 3445 , North Island

(all the possible combination of city and region regardless of postcode). I have wrote some query like this

      var cities = regionsData.DistinctBy(p => 
p.WfRegion).DistinctBy(p=>p.PostCode).DistinctBy(p => p.City).ToList();

But this is giving me a result of first item only like this

        Rodney , 7845 , Auckland

How can I solve this issue?

Answer 1

You need to use GroupBy

var result = regionsData.GroupBy(p => new {p.WfRegion, p.City})
    .Select(g => g.First())
    .ToList();

That will give you groupings by the region and city and then you can just select the first item in each group.