Question

I have a MongoDB database where I store all pictures and when I retrieve them I have stored some doubles, which ain’t so good, but anyway I want to show only distinct elements.

 @foreach (Foto f in fotos.Distinct(new IEqualityComparer<Foto> { )

But the Foto class has one property called smallurl and I want to show only distinct elements by this property. So how to write a custom IEqualityComparer.

Answer 1

Create your own:

public class FotoEqualityComparer : IEqualityComparer<Foto>
{
    public bool Equals(Foto x, Foto y)
    {
         return x.smallurl.Equals(y.smallurl);   
    }

    public int GetHashCode(Foto foto)
    {
         return foto.smallurl.GetHashCode();
    }
}

And use it like so:

fotos.Distinct(new FotoEqualityComparer());

EDIT:

There’s no inline lambda overload of .Distinct() because when two objects compare equal they must have the same GetHashCode return value (or else the hash table used internally by Distinct will not function correctly).

But if you want it in one line, then you could also do grouping to achieve the same result:

fotos.GroupBy(f => f.smallurl).Select(g => g.First());