CSharp/C#, ?? and Guid

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CSharp/C# >> ?? and Guid

by shapper » Mon, 08 Sep 2008 10:29:14 GMT

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
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CSharp/C# >> ?? and Guid

by Kerem Grc » Mon, 08 Sep 2008 10:42:12 GMT


Hi Miguel,

can you show code please,...


Regards

Kerem

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CSharp/C# >> ?? and Guid

by Family Tree Mike » Mon, 08 Sep 2008 11:07:21 GMT

A Guid cannot be null, unless you declare it Guid?.
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CSharp/C# >> ?? and Guid

by shapper » Mon, 08 Sep 2008 12:43:08 GMT


> Kerem G黰r黭c? > Latest Project: http://www.codeplex.com/restarts


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 :-)
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CSharp/C# >> ?? and Guid

by shapper » Mon, 08 Sep 2008 12:44:31 GMT

On Sep 8, 4:07燼m, "Family Tree Mike"




Well, I can do this:

Guid id = new Guid();

And yet the Guid value is not defined.
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CSharp/C# >> ?? and Guid

by Alex Meleta » Mon, 08 Sep 2008 13:06:53 GMT

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
Top

CSharp/C# >> ?? and Guid

by TW9ydGVuIFdlbm5ldmlrIFtDIyBNVlBd » Mon, 08 Sep 2008 13:08:01 GMT


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.

--
Happy Coding!
Morten Wennevik [C# MVP]
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CSharp/C# >> ?? and Guid

by Jon Skeet [C# MVP] » Mon, 08 Sep 2008 13:22:31 GMT


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

--
Jon Skeet - < XXXX@XXXXX.COM >
Web site: http://www.pobox.com/ ~skeet
Blog: http://www.msmvps.com/jon.skeet
C# in Depth: http://csharpindepth.com
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CSharp/C# >> ?? and Guid

by shapper » Mon, 08 Sep 2008 14:01:40 GMT

On Sep 8, 6:08燼m, Morten Wennevik [C# MVP]



> > > Kerem G黰r黭c? > > > Latest Project: http://www.codeplex.com/restarts


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.
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CSharp/C# >> ?? and Guid

by shapper » Mon, 08 Sep 2008 14:02:02 GMT


> Web site: http://www.pobox.com/ ~skeet? > Blog: http://www.msmvps.com/jon.skeet

You are completely right!

Thanks,
Miguel
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