Accessing Guid members in C#

Question

In C++ we can access members of a guid in the following way:

GUID guid = {0}; CoCreateGuid(&guid); dwRand = guid.Data1 & 0x7FFFFFFF;

The structure of guid in C++ is:

Data 1 - unsigned long Data 2 - unsigned short Data 3 - unsigned short Data 4 - unsigned char

Question: How to translate the third line in the C++ code (dwRand = guid.Data1 & 0x7FFFFFFF;). In other words - how to access guid members? There's no such thing in C#.

Thanks in advance!

Is this .NET C++, or standard C++? If the latter, where are you getting your GUID class from? — strager
– strager, Commented Mar 24, 2009 at 21:47
FYI: since some (quite old) version of Windows, GUIDs aren't composed in a simple way from the MAC, date/time and randomizer number or whatever. Try generating a few GUIDs with guidgen. — Anton Tykhyy
– Anton Tykhyy, Commented Mar 24, 2009 at 21:53

Jim Mischel · Accepted Answer · 2009-03-24 22:03:34Z

You can create a structure:

public struct MyGuid { public int Data1; public short Data2; public short Data3; public byte[] Data4; public MyGuid(Guid g) { byte[] gBytes = g.ToByteArray(); Data1 = BitConverter.ToInt32(gBytes, 0); Data2 = BitConverter.ToInt16(gBytes, 4); Data3 = BitConverter.ToInt16(gBytes, 6); Data4 = new Byte[8]; Buffer.BlockCopy(gBytes, 8, Data4, 0, 8); } public Guid ToGuid() { return new Guid(Data1, Data2, Data3, Data4); } }

Now, if you want to modify a Guid:

Guid g = GetGuidFromSomewhere(); MyGuid mg = new MyGuid(g); mg.Data1 &= 0x7FFFFFFF; g = mg.ToGuid();

Jon Skeet · Accepted Answer · 2009-03-24 21:49:51Z

You can use Guid.ToByteArray to get the values as bytes, but there are no accessor methods/properties for the "grouped" bytes. You could always write them as extension methods if you're using C# 3 though.

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