Not-hash-based set collection for storing unique objects with custom equality comparer - C# -

i'm trying store (name: string, value: long) pair in set.

public class namevaluepair {   public string name;   public long value; }  public namevaluepaircomparer comparer = new namevaluepaircomparer(); public hashset<namevaluepair> namevalueset = new hashset<namevaluepair>(comparer); 

two pairs equal if either have equal name or equal value - implemented in namevaluepaircomparer overriding equals method equalitycomparer:

public class namevaluepaircomparer : equalitycomparer<namevaluepair> {    public override bool equals(namevaluepair x, namevaluepair y)    {       return (x.value == y.value) || (x.name == y.name);    } 

the problem is: gethashcode(namevaluepair obj) should return same value 2 objects equals return true, given namevaluepair, gethashcode() should return either value.gethashcode() or name.gethashcode(), have know field in both pairs equal:

   public override int gethashcode(namevaluepair obj)    {       /* ??? */       /* // using unknown reference x         if (obj.value == x.value) return obj.value.gethashcode();         else if (obj.name == x.name) return obj.name.gethashcode();         else return base.gethashcode(obj);       */    } } 

but can't know this, , means can't use hashset store these pairs nor equalitycomparer.

q: there not-hash-based implementation of set in c# (.net 3.5) ?

q: better approach storing unique namevaluepairs custom equality comparer ?

two pairs equal if either have equal name or equal value

you fundamentally can't implement iequalitycomparer<t> correctly these criteria. documentation of equals:

the equals method reflexive, symmetric, , transitive. is, returns true if used compare object itself; true 2 objects x , y if true y , x; , true 2 objects x , z if true x , y , true y , z.

now consider pairs:

x = { "a", 10 }, y = { "a", 20 }, z = { "b", 20 } 

you're saying x , y must equal have same name, , y , z must equal have same value. means (by transitivity) x , z should equal.

as can't implement iequalitycomparer<t> correctly, shouldn't expect relies on correctness work.

i suspect you'll find if @ requirements in more detail, either call 2 collections (one name, 1 value) or don't make sense in light of transitivity.

for example, imagine had set characteristics you've suggested, , add 3 elements above. if add them in order { x, y, z } you'd end single entry. if add them in order { z, x, y } you'd end two. how useful kind of set?