# How can I convert a hex string to a byte array?

### Question

Can we convert a hex string to a byte array using a built-in function in C# or do I have to make a custom method for this?

1
250
6/28/2017 7:16:52 AM

Here's a nice fun LINQ example.

``````public static byte[] StringToByteArray(string hex) {
return Enumerable.Range(0, hex.Length)
.Where(x => x % 2 == 0)
.Select(x => Convert.ToByte(hex.Substring(x, 2), 16))
.ToArray();
}
``````
461
5/3/2011 10:31:09 PM

I did some research and found out that byte.Parse is even slower than Convert.ToByte. The fastest conversion I could come up with uses approximately 15 ticks per byte.

``````    public static byte[] StringToByteArrayFastest(string hex) {
if (hex.Length % 2 == 1)
throw new Exception("The binary key cannot have an odd number of digits");

byte[] arr = new byte[hex.Length >> 1];

for (int i = 0; i < hex.Length >> 1; ++i)
{
arr[i] = (byte)((GetHexVal(hex[i << 1]) << 4) + (GetHexVal(hex[(i << 1) + 1])));
}

return arr;
}

public static int GetHexVal(char hex) {
int val = (int)hex;
//For uppercase A-F letters:
return val - (val < 58 ? 48 : 55);
//For lowercase a-f letters:
//return val - (val < 58 ? 48 : 87);
//Or the two combined, but a bit slower:
//return val - (val < 58 ? 48 : (val < 97 ? 55 : 87));
}
``````

// also works on .NET Micro Framework where (in SDK4.3) byte.Parse(string) only permits integer formats.