Why are there dashes in a .NET GUID?

.net guid uuid
Shawn picture Shawn · Jan 6, 2009 · Viewed 10.6k times · Source

Why are there dashes in a .NET GUID? Are there dashes in most implementations of a GUID, or is it just a Microsoft thing?

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Answer

casperOne picture casperOne · Jan 6, 2009

Technically, there are no "dashes" in a GUID. A GUID is a 128-bit value which is usually stored in the following manner (using C# here to represent the structure):

public struct Guid
{
  public ulong Data1;
  public ushort Data2;
  public ushort Data3;
  public fixed byte Data4[8];
}

The dashes are in the string representation of a GUID.

The dashes are optional and are not required in a string representation of a GUID.

That said, there are historical reasons as to where the placement of the dashes are, related to how the GUIDs were generated, but that historical semantic no longer applies.

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