C# - Define an operator on a struct

Sometimes a struct comes in handy, as it is a value type that cannot be NULL. You can't however write things like a == b on them; that is unless you actualy define what == means for that struct. Take the following struct:

public struct IdName {
  public int Id { get; set; }
  public string Name { get; set; }
}

I simply tell it what == means, but watch out for null's. The compiler will also require that you define !=:

public static bool operator ==(IdName a, IdName b) {
  if ((object)a == null && (object)b == null) return true;
  else if ((object)a != null && (object)b != null) return a.Id == b.Id && a.Name == b.Name;
  else return false;
}
public static bool operator !=(IdName a, IdName b) {
  return !(a == b);
}

Compiling that will give you two warnings: you did not override GetHashCode() nor Equals(). These are necessary to get the underlying infrastructure to work well with the new type. So, implementing the latter should be easy:

• Guidelines for Implementing Equals and the Equality Operator (==)
• Implementing the Equals Method

public override bool Equals(object obj) {
  if (obj != null && obj is IdName)
    return ((IdName)obj).Id == Id && ((IdName)obj).Name == Name;
  else
    return false;
}

And the hashcode thing:

public override int GetHashCode() {
  return base.GetHashCode() ^ Id;
}

And now you can write a == b on structs, just like you can with integers and such.