Operator overloading ==, !=, Equals

Question

I've already gone through question

I understand that, it is necessary to implement ==, != and Equals().

public class BOX {     double height, length, breadth;      // this is first one '=='     public static bool operator== (BOX obj1, BOX obj2)     {         return (obj1.length == obj2.length                      && obj1.breadth == obj2.breadth                      && obj1.height == obj2.height);     }      // this is second one '!='     public static bool operator!= (BOX obj1, BOX obj2)     {         return !(obj1.length == obj2.length                      && obj1.breadth == obj2.breadth                      && obj1.height == obj2.height);     }      // this is third one 'Equals'     public override bool Equals(BOX obj)     {         return (length == obj.length                      && breadth == obj.breadth                      && height == obj.height);     } } 

I assume, I've written code properly to override ==,!=,Equals operators. Though, I get compilation errors as follows.

'myNameSpace.BOX.Equals(myNameSpace.BOX)' is marked as an override  but no suitable method found to override. 

So, question is - How to override above operators & get rid of this error?

Answer 1

As Selman22 said, you are overriding the default object.Equals method, which accepts an object obj and not a safe compile time type.

In order for that to happen, make your type implement IEquatable<Box>:

public class Box : IEquatable<Box> {     double height, length, breadth;      public static bool operator ==(Box obj1, Box obj2)     {         if (ReferenceEquals(obj1, obj2))              return true;         if (ReferenceEquals(obj1, null))              return false;         if (ReferenceEquals(obj2, null))             return false;         return obj1.Equals(obj2);     }     public static bool operator !=(Box obj1, Box obj2) => !(obj1 == obj2);     public bool Equals(Box other)     {         if (ReferenceEquals(other, null))             return false;         if (ReferenceEquals(this, other))             return true;         return height.Equals(other.height)                 && length.Equals(other.length)                 && breadth.Equals(other.breadth);     }     public override bool Equals(object obj) => Equals(obj as Box);      public override int GetHashCode()     {         unchecked         {             int hashCode = height.GetHashCode();             hashCode = (hashCode * 397) ^ length.GetHashCode();             hashCode = (hashCode * 397) ^ breadth.GetHashCode();             return hashCode;         }     } } 

Another thing to note is that you are making a floating point comparison using the equality operator and you might experience a loss of precision.