将 Guid 字符串转换为 BigInteger，反之亦然

Question

I can convert a Guid String into a BigInteger using method below. How can I convert BigInteger back to Guid string.

using System;
using System.Numerics;

class Class1
{       
    public static BigInteger GuidStringToBigInt(string guidString)
    {
        Guid g = new Guid(guidString);
        BigInteger bigInt = new BigInteger(g.ToByteArray());
        return bigInt;
    }

    static void Main(string[] args)
    {
        string guid1 = "{90f0fb85-0f80-4466-9b8c-2025949e2079}";

        Console.WriteLine(guid1);
        Console.WriteLine(GuidStringToBigInt(guid1));
        Console.ReadKey();
    }
}

Answer 1

Please check this:

public static Guid ToGuid(BigInteger value)
{
     byte[] bytes = new byte[16];
     value.ToByteArray().CopyTo(bytes, 0);
     return new Guid(bytes);
}

Edit: Working Fiddle

Answer 2

If you want positive integer representations the conversion in the question and the reverse conversion in the accepted answer both don't work for all values. For example, converting from ffffffff-ffff-ffff-ffff-ffffffffffff to a BigInteger will give -1 . And converting from 340282366920938463463374607431768211455 to a Guid will give an exception.

If you do want the positive representation (useful if you're trying to convert bases, for example) you'll need to add an additional byte with the value zero to the end of your byte array. (See this illustration for a positive values right before the frist "Remarks" section).

public static BigInteger GuidStringToBigIntPositive(string guidString)
{
    Guid g = new Guid(guidString);
    var guidBytes = g.ToByteArray();
    // Pad extra 0x00 byte so value is handled as positive integer
    var positiveGuidBytes = new byte[guidBytes.Length + 1];
    Array.Copy(guidBytes, positiveGuidBytes, guidBytes.Length);

    BigInteger bigInt = new BigInteger(positiveGuidBytes);
    return bigInt;
}

public static string BigIntToGuidStringPositive(BigInteger bigint)
{
    // Allocate extra byte to store the large positive integer
    byte[] positiveBytes = new byte[17];
    bigint.ToByteArray().CopyTo(positiveBytes, 0);
    // Strip the extra byte so Guid can handle it
    byte[] bytes = new byte[16];
    Array.Copy(positiveBytes, bytes, bytes.Length);
    return new Guid(bytes).ToString();
}

Fiddle demonstrating both methods.