I have a class similar to below:
class Abc { public string A {get;set;} public string B {get;set;} } The criteria for equals is if any of A or B matches two objects of class Abc should match.
public override bool Equals (Abc obj) { if (obj.A == A || obj.B == B) return true; else return false; } Can anyone let me know what kind of GetHashCode function would give equal values in such cases.
Because both A & B fields may or may not have same values.
The one and only must-have requirement for implementing GetHashCode is that when two objects are considered equal (i.e. Equals returns true), then their hash codes must match.
In your case, if you have two different objects with x = (A1, B1) and y = (A2, B2), then their hash code must be the same because it must be the same as z = (A1, B2), because x and z are considered equal and so are y and z. Therefore, the only valid implementation of GetHashCode is to always return a constant number, for example 0.
You might wonder because a GetHashCode implementation that simply returns a constant number makes no sense and that is true; the reason is that your Equals also does not make sense. Your biggest problem is that Equals is not transitive. x and z are equal and z and y are, but x and y are not. This is contrary to what you would expect.
Equalsmethod - it must be&&, not||.||.