I understand that if we wanna compare two objects of the same class,
we need to implement the IComparable interface, as shown here:

http://msdn.microsoft.com/en-us/library/system.icomparable.compareto(printer).aspx

I am confused by the implementation of the CompareTo method in the C#
example on the above page. Look:

public int CompareTo(object obj)
{
if(obj is Temperature)
{
Temperature otherTemperature = (Temperature) obj;
return
this.temperatureF.CompareTo(otherTemperature.temperatureF);
}
else
{
throw new ArgumentException("object is not a Temperature");
}
}

The thing that baffles me is that the implementation of CompareTo
makes a call to this method itself. Hey, CompareTo is *not*
implemented in the interface (no interfaces implements a method), and
*we* are trying to implement it, then how are we able to call this
method in order to implement it? I don't understand the logic here.

Instead, I thought that the implementation of CompareTo in this case
should really be this:

public int CompareTo(object obj)
{
if(obj is Temperature)
{
Temperature otherTemperature = (Temperature) obj;
if (this.temperatureF < otherTemperature)
{ return -1; }
else if ((this.temperatureF == otherTemperature)
{ return 0; }
else
{ return 1; }
}
else
{
throw new ArgumentException("object is not a Temperature");
}
}

Dear gurus, so what is the reason behind calling CompareTo itself when
implementing it? Thank you.

Author <(E-Mail Removed)> wrote:
> I understand that if we wanna compare two objects of the same class,
> we need to implement the IComparable interface, as shown here:
>
> http://msdn.microsoft.com/en-us/library/system.icomparable.compareto(printer).aspx
>
> I am confused by the implementation of the CompareTo method in the C#
> example on the above page. Look:
>
> public int CompareTo(object obj)
> {
> if(obj is Temperature)
> {
> Temperature otherTemperature = (Temperature) obj;
> return
> this.temperatureF.CompareTo(otherTemperature.temperatureF);
> }
> else
> {
> throw new ArgumentException("object is not a Temperature");
> }
> }
>
> The thing that baffles me is that the implementation of CompareTo
> makes a call to this method itself.

Where? It looks to me like it's calling double's implementation of
CompareTo.

--
Jon Skeet - <(E-Mail Removed)>
Web site: http://www.pobox.com/~skeet
Blog: http://www.msmvps.com/jon_skeet
C# in Depth: http://csharpindepth.com

On Jul 10, 3:08*pm, Jon Skeet [C# MVP] <sk...@pobox.com> wrote:
> Author <gnewsgr...@gmail.com> wrote:
> > I understand that if we wanna compare two objects of the same class,
> > we need to implement the IComparable interface, as shown here:
>
> >http://msdn.microsoft.com/en-us/library/system.icomparable.compareto(...
>
> > I am confused by the implementation of the CompareTo method in the C#
> > example on the above page. *Look:
>
> > public int CompareTo(object obj)
> > {
> > * * * * if(obj is Temperature)
> > * * * * {
> > * * * * * * Temperature otherTemperature = (Temperature) obj;
> > * * * * * * return
> > this.temperatureF.CompareTo(otherTemperature.temperatureF);
> > * * * * }
> > * * * * else
> > * * * * {
> > * * * * * *throw new ArgumentException("object is not a Temperature");
> > * * * * }
> > }
>
> > The thing that baffles me is that the implementation of CompareTo
> > makes a call to this method itself.
>
> Where? It looks to me like it's calling double's implementation of
> CompareTo.
>
> --
> Jon Skeet - <sk...@pobox.com>
> Web site:http://www.pobox.com/~skeet*
> Blog:http://www.msmvps.com/jon_skeet
> C# in Depth:http://csharpindepth.com

That's right. So, double actually implements CompareTo like what I
did. That must be it. Thank you.

On Jul 10, 3:08*pm, Jon Skeet [C# MVP] <sk...@pobox.com> wrote:
> Author <gnewsgr...@gmail.com> wrote:
> > I understand that if we wanna compare two objects of the same class,
> > we need to implement the IComparable interface, as shown here:
>
> >http://msdn.microsoft.com/en-us/library/system.icomparable.compareto(...
>
> > I am confused by the implementation of the CompareTo method in the C#
> > example on the above page. *Look:
>
> > public int CompareTo(object obj)
> > {
> > * * * * if(obj is Temperature)
> > * * * * {
> > * * * * * * Temperature otherTemperature = (Temperature) obj;
> > * * * * * * return
> > this.temperatureF.CompareTo(otherTemperature.temperatureF);
> > * * * * }
> > * * * * else
> > * * * * {
> > * * * * * *throw new ArgumentException("object is not a Temperature");
> > * * * * }
> > }
>
> > The thing that baffles me is that the implementation of CompareTo
> > makes a call to this method itself.
>
> Where? It looks to me like it's calling double's implementation of
> CompareTo.
>
> --
> Jon Skeet - <sk...@pobox.com>
> Web site:http://www.pobox.com/~skeet*
> Blog:http://www.msmvps.com/jon_skeet
> C# in Depth:http://csharpindepth.com

I had thought it was this.CompareTo(that.temperature).