Answer by oerkelens for Convert a hex string to base64

You first need to convert your hexstring to a byte-array, which you can then convert to base-64.

To convert from your hexstring to Base-64, you can use:

 public static string HexString2B64String(this string input)
 {
     return System.Convert.ToBase64String(input.HexStringToHex());
 }

Where HexStringToHex is:

public static byte[] HexStringToHex(this string inputHex)
{
    var resultantArray = new byte[inputHex.Length / 2];
    for (var i = 0; i < resultantArray.Length; i++)
    {
        resultantArray[i] = System.Convert.ToByte(inputHex.Substring(i * 2, 2), 16);
    }
    return resultantArray;
}