How to use Guids in C#?

Question

This Code:

Something = new Guid()

is returning:

00000000-0000-0000-0000-000000000000

all the time and I can't tell why? So, why?

Possible duplicate of [C# how to create a Guid value?](http://stackoverflow.com/questions/2344098/c-sharp-how-to-create-a-guid-value) — StayOnTarget, May 09 '17 at 13:52

score 149 · Accepted Answer · edited May 24 '09 at 15:59

149

You should use Guid.NewGuid()

edited May 24 '09 at 15:59

Randolpho

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answered May 24 '09 at 15:46

Will Dean

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@Ante: If you have the Guid class then you have the NewGuid method. – Guffa May 24 '09 at 16:07

score 61 · Answer 2 · answered May 24 '09 at 15:51

Just a quick explanation for why you need to call NewGuid as opposed to using the default constructor... In .NET all structures (value types like int, decimal, Guid, DateTime, etc) must have a default parameterless constructor that initializes all of the fields to their default value. In the case of Guid, the bytes that make up the Guid are all zero. Rather than making a special case for Guid or making it a class, they use the NewGuid method to generate a new "random" Guid.

score 12 · Answer 3 · answered May 24 '09 at 16:01

12

It's in System.Guid.

To dynamically create a GUID in code:

Guid messageId = System.Guid.NewGuid();

To see its value:

string x = messageId.ToString();

answered May 24 '09 at 16:01

DOK

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Yes, it should be there (http://msdn.microsoft.com/en-us/library/system.guid_members.aspx) but I can't use it. Why? – Ante May 24 '09 at 16:06
"I can't use it" - what happens when you try to use it? Type it out manually (perhaps there's an issue with your intellisense) and try to compile - do you get compilation errors? – Matt Brindley May 24 '09 at 16:14
What do you mean when you say you "can't use it"? If you type Guid x = System.Guid.NewGuid() and compile, do you get an error? Or do you not like the value you're getting for x? – DOK May 24 '09 at 16:17
LOL yea that Guid algorithm sometimes needs a fresh reboot. Sigh. – Josh Jul 21 '11 at 21:42

score 4 · Answer 4 · edited Feb 05 '14 at 10:30

4

something = new Guid() equals something = Guid.Empty.

Use Guid.NewGuid(); instead

edited Feb 05 '14 at 10:30

Kaushik

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answered Sep 26 '12 at 13:57

Will Yu

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score 3 · Answer 5 · edited Sep 21 '12 at 21:30

3

 Guid g1 = Guid.NewGuid();

 string s1;
 s1 = g1.ToString();
 Console.WriteLine("{0}",s1);
 Console.ReadKey();

edited Sep 21 '12 at 21:30

Andrew Barber

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answered Sep 03 '12 at 07:13

Leo

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How to use Guids in C#?

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