IEquatable - Best practice override for .Equals(object obj) in C#

IEquatable - Best practice override for .Equals(object obj) in C#

Whenever I write a new class or struct that is likely to hold some data,
that may need to be compared, I always implement IEquatable<T> as this
provides the class/struct with a strongly 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 well as providing an implementation for .Equals(Radius other), I should
really override the default implementation too (.Equals(object obj))
I have two options here, and my question is, which of these
implementations is better?
Option 1 is to use casting:
public override bool Equals(object obj)
{
return this.Equals((Radius)obj);
}
Option 2 is to use the "as" keyword:
public override bool Equals(object obj)
{
return this.Equals(obj as Radius);
}
My reason for asking this is, using casting will throw an exception if obj
cannot be cast to Radius, whereas as will resolve to null if it cannot be
cast, therefore it just checks this against null, without throwing an
exception; So is it better to throw an exception, or to just return false?