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Asked: 2026-05-27T17:59:59+00:00

Possible Duplicate: Are automatically generated GUIDs for types in .NET consistent? I want to

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Possible Duplicate:
Are automatically generated GUIDs for types in .NET consistent?

I want to use Type as a key dictionary, but I’d rather use either full type name or Type.GUID. How reliable and correct is Type.GUID for this task?

Ayende Rahien writes:

Can you rely on System.Type.GUID to be stable?

By stable I mean that it will generate the same value for the same type across compilations. Empirical evidence suggest that this is the case, with the following factors determining the Guid of a type:

  • Type name (including the namespace)
  • Assembly name
  • Assembly public key

Reflectoring into the system, it turns out that System.Type.GUID is
eventually translated to a call to System.RuntimeType.GetGUID, this is
one of the scary InternallCall method that are implemented directly in
the runtime itself.

I wonder…

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1 Answer

  1. Editorial Team

    From the documentation at http://msdn.microsoft.com/en-us/library/system.type.guid.aspx.

    The purpose of Type.GUID is to get the value associated with the class using [Guid("...")]. However, it also returns a guid when this attribute is not associated. The problem is where it gets this. A small test shows that the guid is stable. I checked the guid of a class, and verified that it changed when I renamed the class. When I renamed the class back, I got the original guid again. However, since these guids appear out of thin air, they shouldn’t be trusted to be stable over time, releases, framework versions, etc.

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