Convert Hex to Readable String and Readable Text to Hex

private static readonly  char[] HexChars = "0123456789ABCDEF".ToCharArray();

private static string ConvertToHex(string ascii)
{
if (ascii == null) return null;
if (ascii == "") return "";

byte[] bytes = Encoding.UTF8.GetBytes(ascii);

StringBuilder converted = new StringBuilder(bytes.Length * 2);

foreach (byte b in bytes)
{
converted.Append(HexChars[b >> 4]);
converted.Append(HexChars[b & 0xf]);
}

return converted.ToString();
}

private static string ConvertFromHex(string hex)
{
if (hex == null) return null;
if (hex == "") return "";
if (hex.Length % 2 != 0)
throw new ApplicationException("hex string length should be divisble by 2: " + hex);

byte[] bytes = new byte[hex.Length / 2];

for (int i = 0; i < bytes.Length; i++)
bytes[i] = byte.Parse(hex[2 * i] + "" + hex[2 * i + 1], NumberStyles.HexNumber);

string converted = Encoding.UTF8.GetString(bytes);

if (converted[converted.Length - 1] == '\0')
converted = converted.Remove(converted.Length - 1, 1);

return converted;
}