.net - IEquatable<T> - Best practice override for .Equals(object obj) in C# -

whenever write new class or struct hold data, may need compared, implement iequatable<t> provides class/struct typed .equals(t other) method.

example:

public struct radius : iequatable<radius> {     public int32 topleft { get; set; }     public int32 topright { get; set; }     public int32 bottomleft { get; set; }     public int32 bottomright { get; set; }      public bool equals(radius other)     {         return this.topleft == other.topleft             && this.topright == other.topright             && this.bottomleft == other.bottomleft             && this.bottomright == other.bottomright;     } } 

as providing implementation .equals(radius other), should override default implementation (.equals(object obj))

i have 2 options here, , question is, of these implementations better?

option 1 use casting:

public override bool equals(object obj) {     return this.equals((radius)obj); } 

option 2 use "as" keyword:

public override bool equals(object obj) {     return this.equals(obj radius); } 

my reason asking is, using casting throw exception if obj cannot cast radius, whereas as resolve null if cannot cast, therefore checks this against null, without throwing exception; better throw exception, or return false?

edit: has been pointed out quite few fellow so'ers, structs cannot null, therefore second option not apply struct. therefore question springs mind: should overridden implementation of .equals(object obj) identical structs , classes?

the equals() method must never throw exception.

an object of different type merely unequal.

quoting documentation:

implementations of equals must not throw exceptions; should return value. example, if obj null, equals method should return false instead of throwing argumentnullexception.