Remove duplicates in the list using linq

Question

I have a class Items with properties (Id, Name, Code, Price).

The List of Items is populated with duplicated items.

For ex.:

1         Item1       IT00001        $100
2         Item2       IT00002        $200
3         Item3       IT00003        $150
1         Item1       IT00001        $100
3         Item3       IT00003        $150

How to remove the duplicates in the list using linq?

Answer 1

var distinctItems = items.Distinct();

To match on only some of the properties, create a custom equality comparer, e.g.:

class DistinctItemComparer : IEqualityComparer<Item> {

    public bool Equals(Item x, Item y) {
        return x.Id == y.Id &&
            x.Name == y.Name &&
            x.Code == y.Code &&
            x.Price == y.Price;
    }

    public int GetHashCode(Item obj) {
        return obj.Id.GetHashCode() ^
            obj.Name.GetHashCode() ^
            obj.Code.GetHashCode() ^
            obj.Price.GetHashCode();
    }
}

Then use it like this:

var distinctItems = items.Distinct(new DistinctItemComparer());

Answer 2

Use Distinct() but keep in mind that it uses the default equality comparer to compare values, so if you want anything beyond that you need to implement your own comparer.

Please see http://msdn.microsoft.com/en-us/library/bb348436.aspx for an example.

Answer 3

If there is something that is throwing off your Distinct query, you might want to look at MoreLinq and use the DistinctBy operator and select distinct objects by id.

var distinct = items.DistinctBy( i => i.Id );