How to define the operator ==

Question

Given the class as follows,

public class Number
{
  public int X { get; set; }
  public int Y { get; set; }
}

How to define an overload operato

Answer 1

overload the operator yourself:

public static bool operator ==(Number a, Number b)
{
    // do stuff
    return true/false;
}

Answer 2

Here is a short example of how to do it, but I very strongly recommend reading Guidelines for Overloading Equals() and Operator == (C# Programming Guide) to understand the interaction between Equals() and == and so on.

public class Number
{
  public int X { get; set; }
  public int Y { get; set; }

  public static bool operator ==(Number  a, Number b)
  {
    // TODO
  }
}

Answer 3

From the MSDN Docs:

public static bool operator ==(ThreeDPoint a, ThreeDPoint b)
{
    // If both are null, or both are same instance, return true.
    if (System.Object.ReferenceEquals(a, b))
    {
        return true;
    }

    // If one is null, but not both, return false.
    if (((object)a == null) || ((object)b == null))
    {
        return false;
    }

    // Return true if the fields match:
    return a.x == b.x && a.y == b.y && a.z == b.z;
}

public static bool operator !=(ThreeDPoint a, ThreeDPoint b)
{
    return !(a == b);
}

Answer 4

public static bool operator ==(YourClassType a, YourClassType b)
{
    // do the comparison
}

More information here. In short:

• Any type that overloads operator == should also overload operator !=
• Any type that overloads operator == should also should override Equals
• It is recommended that any class that overrides Equals also override GetHashCode