Convert Type Decimal to Hex (string) in .NET 3.5

Question

I am trying to convert a Decimal to Hex as a string. I've looked all over for a solution to this, but all I can find is Int or long to Hex. When using the code below I receive a "Format specifier was invalid" error.

    Decimal decValue = 18446744073709551615
    string hexValue = decValue.ToString("X");

I've also looked into converting the decimal to a byte array and then converting to Hex, but I'm coming up short on that also.

Answer 1

Since you're using .NET 3.5, how about IntX which will work for .NET 2.0+?

var intx = new Oyster.Math.IntX(decValue.ToString());
intx.ToString(16);

For .NET 4.0+ use System.Numerics (remember to include System.Numerics.dll )

Decimal decValue = 18446744073709551615;
var bigValue = new BigInteger(decValue);
bigValue.ToString("X");

Of course this ignores any portion that is non-integer.

Answer 2

Since you're using .NET 3.5, you'll have to do it by hand. You can wrap it up nice and neat in an extension method:

public static class DecimalHelper {
public static string ToHexString( this Decimal dec ) {
    var sb = new StringBuilder();
    while( dec > 1 ) {
        var r = dec % 16;
        dec /= 16;
        sb.Insert( 0, ((int)r).ToString( "X" ) );
    }
    return sb.ToString();
    }
}

Then just call it like this:

Decimal dec = 18446744073709551615;
var hex = dec.ToHexString();