Guid NewGuid vs new Guid

Question

What s the difference between Guid NewGuid   and new Guid     Which one is preferred

User · Accepted Answer

new Guid   makes an  empty  all-0 guid  00000000-0000-0000-0000-000000000000 is not very useful    Guid NewGuid   makes an actual guid with a unique value  what you probably want

User · Answer

I understand this is an old thread  just adding some more detail  The two answers by Mark and Jon Hanna sum up the differences  albeit it may interest some that   Guid NewGuid     Eventually calls CoCreateGuid  a COM call to Ole32   reference here  and the actual work is done by UuidCreate   Guid Empty is meant to be used to check if a Guid contains all zeroes  This could also be done via comparing the value of the Guid in question with new Guid    So  if you need a unique identifier  the answer is Guid NewGuid

User · Answer

Guid NewGuid   creates a new UUID using an algorithm that is designed to make collisions very  very unlikely   new Guid   creates a UUID that is all-zeros   Generally you would prefer the former  because that s the point of a UUID  unless you re receiving it from somewhere else of course    There are cases where you do indeed want an all-zero UUID  but in this case Guid Empty or default Guid  is clearer about your intent  and there s less chance of someone reading it expecting a unique value had been created   In all  new Guid   isn t that useful due to this lack of clarity  but it s not possible to have a value-type that doesn t have a parameterless constructor that returns an all-zeros-and-nulls value   Edit  Actually  it is possible to have a parameterless constructor on a value type that doesn t set everything to zero and null  but you can t do it in C   and the rules about when it will be called and when there will just be an all-zero struct created are confusing  so it s not a good idea anyway

User · Answer

Guid NewGuid    as it creates GUIDs as intended   Guid NewGuid   creates an empty Guid object  initializes it by calling CoCreateGuid and returns the object   new Guid   merely creates an empty GUID  all zeros  I think    I guess they had to make the constructor public as Guid is a struct

[c#] Guid.NewGuid() vs. new Guid()

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