String literal to byte

Question

I am making a forms application is Visual C#. I have a textbox where a user must enter a number and a uppercase letter, example "9D".

What I need to do is put that letter into a byte array as a byte...so in my byte array it would:

array[index] = 0x9D

I know that the textbox class represents the 9D as a string. I am confused on how to make it into a literal byte (9D) and stick it in the array.

New to .Net so any help would be appreciated. I've looked at the System.Convert class and don't see anything I can use.

Answer 1

Use Byte.Parse(string, NumberStyles):

byte b = Byte.Parse(text, NumberStyles.HexNumber);

Or Byte.TryParse(string, NumberStyles, IFormatProvider, out Byte) to more gracefully handle invalid input.

Answer 2

If you wanted it done a little faster and to allow '0x' in front of the number you can use Convert.ToByte("0x9D", 16). In my limited testing, Convert.ToByte was twice as fast as Byte.Parse

You can also validate the input with a simple Regex. This way you know the string will parse before calling any method to parse or convert it.

// Checks that the string is either 2 or 4 characters and contains only valid hex
var regex = new Regex(@"^(0x)*[a-fA-F\d]{2}$")

Test code:

const int count = 100000;
var data = "9D";
var sw = new Stopwatch();
sw.Reset();

byte dest = 0;
sw.Start();
for(int i=0; i < count; ++i)
{
    dest = Byte.Parse(data, NumberStyles.AllowHexSpecifier);
}
sw.Stop();
var parseTime = sw.ElapsedMilliseconds;
sw.Reset();
sw.Start();
for(int i=0; i < count; ++i)
{
    dest = Convert.ToByte(data, 16);
}
sw.Stop();
var convertTime = sw.ElapsedMilliseconds;

Answer 3

Use Byte.Parse to parse a string into a Byte.

array[index] = Byte.Parse("9D", NumberStyles.AllowHexSpecifier);

Note that having the prefix 0x will cause a parse fail, so you may want to strip it out if it exists.