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                       amp  amp  obj1 breadth    obj2 breadth                       amp  amp  obj1 height    obj2 height                 this is second one          public static bool operator    BOX obj1  BOX obj2                return   obj1 length    obj2 length                       amp  amp  obj1 breadth    obj2 breadth                       amp  amp  obj1 height    obj2 height                 this is third one  Equals      public override bool Equals BOX obj                return  length    obj length                       amp  amp  breadth    obj breadth                       amp  amp  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  amp  get rid of this error

User · Answer

public class BOX       double height  length  breadth       public static bool operator     BOX b1  BOX b2                if  b1 is null              return b2 is null           return b1 Equals b2              public static bool operator     BOX b1  BOX b2                return   b1    b2              public override bool Equals object obj                if  obj    null              return false           return obj is BOX b2   length    b2 length  amp  amp                                  breadth    b2 breadth  amp  amp                                  height    b2 height   false              public override int GetHashCode                 return  height length breadth  GetHashCode

User · Answer

I think you declared the Equals method like this   public override bool Equals BOX obj    Since the object Equals method takes an object  there is no method to override with this signature  You have to override it like this   public override bool Equals object obj    If you want type-safe Equals  you can implement IEquatable lt BOX gt

User · Answer

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 lt Box gt    public class Box   IEquatable lt Box gt        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                return   obj1    obj2              public bool Equals Box other                if  ReferenceEquals other  null                         return false                    if  ReferenceEquals this  other                         return true                     return height Equals other height                   amp  amp  length Equals other length                   amp  amp  breadth Equals other breadth              public override bool Equals object obj                return 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

User · Answer

In fact  this is a  how to  subject  So  here is the reference implementation       public class BOX               double height  length  breadth           public static bool operator     BOX b1  BOX b2                        if   object b1    null                  return  object b2    null               return b1 Equals b2                      public static bool operator     BOX b1  BOX b2                        return   b1    b2                      public override bool Equals object obj                        if  obj    null    GetType      obj GetType                    return false               var b2    BOX obj              return  length    b2 length  amp  amp  breadth    b2 breadth  amp  amp  height    b2 height                      public override int GetHashCode                         return height GetHashCode     length GetHashCode     breadth GetHashCode                      REF  https   msdn microsoft com en-us library 336aedhh v vs 100  aspx Examples  UPDATE  the cast to  object  in the operator    implementation is important  otherwise  it would re-execute the operator    overload  leading to a stackoverflow  Credits to  grek40   This  object  cast trick is from Microsoft String    implementaiton  SRC  https   github com Microsoft referencesource blob master mscorlib system string cs L643

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