.NET Native GUID conversion

Question

I have an external database that is feeding information to me. One saves their data as native GUID format and my other data source supplies standard .NET GUID format string.

Is there a tidy way to convert from Native GUID to GUID Structure?

Also is there any validation bit to determine if a provided value is a Native GUID or not? I can't seem to find any if there is one.

The difference is as follows:

typedef struct _GUID 
{  
   DWORD Data1;  
   WORD Data2;  
   WORD Data3;  
   BYTE Data4[8];
} GUID;

Data1, Data2 and Data3 get their byte order reversed but Data4 remains the same, see http://en.wikipedia.org/wiki/Globally_unique_identifier for more info

Answer 1

To see if the input is in little Endian or not BitConverter.IsLittleEndinan() helps.

I just had to do this same thing and using Paul Smith's answer above I got it working with this code. Derived off his code but with a fix on last byte swap order and condensed to one flip ensuring guid.FlipEndian().FlipEndian() == guid.

C# Code:

public static class Extensions
{
    /// <summary>
    /// A CLSCompliant method to convert a big-endian Guid to little-endian
    /// and vice versa.
    /// The Guid Constructor (UInt32, UInt16, UInt16, Byte, Byte, Byte, Byte,
    ///  Byte, Byte, Byte, Byte) is not CLSCompliant.
    /// </summary>
    [CLSCompliant(true)]
    public static Guid FlipEndian(this Guid guid)
    {
        var newBytes = new byte[16];
        var oldBytes = guid.ToByteArray();

        for (var i = 8; i < 16; i++)
            newBytes[i] = oldBytes[i];

        newBytes[3] = oldBytes[0];
        newBytes[2] = oldBytes[1];
        newBytes[1] = oldBytes[2];
        newBytes[0] = oldBytes[3];
        newBytes[5] = oldBytes[4];
        newBytes[4] = oldBytes[5];
        newBytes[6] = oldBytes[7];
        newBytes[7] = oldBytes[6];

        return new Guid(newBytes);
    }
}

VB.net code (Translated from online service):

Imports System.Runtime.CompilerServices

Module ModuleExtension

    ''' <summary>
    ''' A CLSCompliant method to convert a big-endian Guid to little-endian
    ''' and vice versa.
    ''' The Guid Constructor (UInt32, UInt16, UInt16, Byte, Byte, Byte, Byte,
    '''  Byte, Byte, Byte, Byte) is not CLSCompliant.
    ''' </summary>
    <Extension()>
    Public Function FlipEndian(guid As Guid) As Guid
        Dim newBytes = New Byte(15) {}
        Dim oldBytes = guid.ToByteArray()

        For i As Integer = 8 To 15
            newBytes(i) = oldBytes(i)
        Next

        newBytes(3) = oldBytes(0)
        newBytes(2) = oldBytes(1)
        newBytes(1) = oldBytes(2)
        newBytes(0) = oldBytes(3)
        newBytes(5) = oldBytes(4)
        newBytes(4) = oldBytes(5)
        newBytes(6) = oldBytes(7)
        newBytes(7) = oldBytes(6)

        Return New Guid(newBytes)
    End Function

End Module