?? and Guid

[shapper]

Hello,

I am inserting an item on a XML file and I have something like this:

paper.ID ?? Guid.NewGuid()

Basically my idea was that if paper.ID is null then create a new Guid.

It says it is not possible to use ?? with Guid. Is there another
option to do this?

Thanks,
Miguel

 

[Kerem Gümrükcü]

Hi Miguel,

can you show code please,...


Regards

Kerem

--

 

[Family Tree Mike]

A Guid cannot be null, unless you declare it Guid?.

 

[shapper]

Hi Miguel,

can you show code please,...

Regards

Kerem

--
-----------------------
Beste Grüsse / Best regards / Votre bien devoue
Kerem Gümrükcü
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album.Add(new XElement("img",
new XAttribute("id", paper.Slide.SlideID ??
Guid.NewGuid())
));

paper.Slide is an object. So if it's SlideID, which is Guid, had no
value assigned then a new guid is used.

This seemed logic to me until I got the error

 

[shapper]

A Guid cannot be null, unless you declare it Guid?.

Well, I can do this:

Guid id = new Guid();

And yet the Guid value is not defined.

 

[Alex Meleta]

Hi shapper,

Yes, but cant Guid id = null. Basicaly, ?? aplied for reference and nullable
types.
http://msdn.microsoft.com/en-us/library/ms173224(VS.80).aspx

Regards, Alex
blog: devkids.blogspot.com

 

[Morten Wennevik [C# MVP]]

album.Add(new XElement("img",
new XAttribute("id", paper.Slide.SlideID ??
Guid.NewGuid())
));

paper.Slide is an object. So if it's SlideID, which is Guid, had no
value assigned then a new guid is used.

This seemed logic to me until I got the error

Since SlideID is a Guid it cannot be null. Therefore SlideID ?? makes no
sense. Now, if you make SlideID a Guid? (nullable Guid) your code should
work.

 

[Jon Skeet [C# MVP]]

Well, I can do this:

Guid id = new Guid();

And yet the Guid value is not defined.

Yes it is. That's a well-defined Guid of all zeroes. It's sort of like
the empty string of Guids.

 

[shapper]

Since SlideID is a Guid it cannot be null.  Therefore SlideID ?? makes no
sense.  Now, if you make SlideID a Guid? (nullable Guid) your code should
work.

I see. I think I will let it this way because it is generated by Linq
To SQL dbml and I prefer to touch the least possible in the generated
code.

 

[shapper]

Yes it is. That's a well-defined Guid of all zeroes. It's sort of like
the empty string of Guids.

--
Jon Skeet - <[email protected]>
Web site:http://www.pobox.com/~skeet 
Blog:http://www.msmvps.com/jon.skeet
C# in Depth:http://csharpindepth.com

You are completely right!

Thanks,
Miguel