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Converting Hexadecimal String to/from Byte Array in C#

, 6 May 2003
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Provides and demonstrates a hexadecimal string encoding/decoding class

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Introduction

While the .NET framework provides methods to convert a byte array into a Hexadecimal string ( byte.ToString(“X”) ), it is not so easy to convert a hexadecimal string back into a byte array. Such a function is useful when you need to backup data from your application on paper, such as an encryption key, and later, convert it back into data after the user types it in.

The HexEncoding class provided here, contains functions which allow for the conversion of a string in hexadecimal format into a byte array, and back. It also contains functions which lets you check the formatting of the string before conversion, and how many bytes a given string will produce.

Background

In a hexadecimal string, one byte is represented two hexadecimal characters. A hexadecimal character has a value of (A-F, 0-9).

e.g. string “01FFA0” is equivalent to byte[] { 1, 255, 160 }

Using the code

HexEncoding is the name of the class I created with static functions for hexadecimal string conversion.

Here’s a sample of how it is used, when the Convert button is clicked like on the screenshot:

private void button1_Click(object sender, System.EventArgs e)
{
    string hexString = txtHex.Text;
    int discarded;
    txtByteCount.Text = ((int)HexEncoding.GetByteCount(hexString)).ToString();
    txtLength.Text = hexString.Length.ToString();
    byte[] byteArray = HexEncoding.GetBytes(hexString, out discarded);
    txtDiscard.Text = discarded.ToString();
    string temp = "";
    for (int i=0; i<byteArray.Length; i++)
    {
        temp += byteArray[i].ToString("D3") + " ";
    }
    txtByte.Text = temp;
    txtHex2.Text = HexEncoding.ToString(byteArray);
}

HexEncoding.GetByteCount(string hexString) returns the number of bytes that will be generated from the hexString.

HexEncoding.GetBytes(string hexString, out int discarded) returns the byte array converted from the hexString, and the second parameter returns the number of non-hexadecimal characters that were ignored in the string. This includes dashes, whitespace, and letters after ‘F’.

HexEncoding.ToString(byte[]) returns the newly converted byte array back into string form. Notice the ‘-‘ characters are now missing.

The key function provided by the framework to convert a hexadecimal string to a single byte is this:

// byte newByte = byte.Parse(hex, System.Globalization.NumberStyles.HexNumber);

where “hex” is of the form “1A”, “00”, “FF”, etc.

Thanks to Polux on the .NET 247 newsgroups who posted the int.Parse(...) answer to another hexadecimal question.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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neilck

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Comments and Discussions

 
GeneralJust what I needed PinmemberJoe Pardue16-Jun-05 5:05 
GeneralGreatly Appreciated! PinmemberDevon Knight13-Apr-05 13:58 
GeneralFastest I found.. Pinmemberstotti_no121-Mar-05 21:05 
AnswerRe: Fastest I found.. Pinmembertomstrummer28-Jul-07 7:07 
Generalincrease speed PinmemberCyberDEF3-Feb-05 11:02 
Generalthanks a lot Pinsusswilson_o23-Jan-05 16:46 
Generalabout discarded Pinmemberyzh_x9-Jan-05 16:42 
GeneralThanks yeah :) Pinmemberchuawenching9-Sep-04 16:17 
This articles had saves my time of coding the hex to bytes. Thanks again Smile | :) I love the stringbuilder part...
GeneralImprove performance PinmemberEsteves15-Nov-03 17:05 
GeneralVery good Pinmembermikeperetz5-Sep-03 11:11 
GeneralRe: Very good Pinmemberbobseadream9-May-04 5:58 
GeneralPerformance improvement PinmemberPatrik Reali3-Jul-03 5:37 
GeneralRe: Performance improvement Pinmemberneilck3-Jul-03 6:59 
GeneralRe: Performance improvement PinmemberVolker von Einem6-Feb-07 3:34 
GeneralThanks Pinmemberjmandile24-Jun-03 15:26 
GeneralAnother way PinmemberPhillip Vetter13-May-03 0:31 
GeneralRe: Another way Pinmemberslick_bytes27-Nov-03 18:57 
GeneralRe: Another way using array of bytes PinmemberLarry102425-Feb-04 5:05 
GeneralRe: Another way PinmemberDarkStarPL12-Feb-07 22:49 
GeneralYou can use System.Text.Encoding.ASCII.* too... PinmemberJhon12-May-03 20:19 
GeneralRe: You can use System.Text.Encoding.ASCII.* too... Pinmemberyizumi2-Dec-04 14:30 
GeneralCoincidentally, I wrote the same function a week ago Pinmembercrowdozer8-May-03 8:01 
GeneralRe: Coincidentally, I wrote the same function a week ago Pinmemberneilck9-May-03 4:57 
GeneralRe: Coincidentally, I wrote the same function a week ago PinsussAnonymous19-Mar-04 19:40 
GeneralVery nice PinmemberMarcin7-May-03 10:35 

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