Try this:
char[] input = "Hello! This is text.".ToCharArray();
char[] output = new char[64];
Array.Copy(input, output, input.Length);
for(int i = 0; i < output.Length; i++)
{
char c = output[i];
Console.WriteLine("{0}:{1:X02}", char.IsControl(c) ? '*' : c, (int)c);
}