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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

Sample Image

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.

A list of licenses authors might use can be found here

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neilck

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Comments and Discussions

 
GeneralMy vote of 2 PinmemberHaiSonTran12-Apr-11 19:25 
GeneralGreat job Pinmembermapelo6329-Jan-10 16:23 
GeneralExplanation on "D3" PinmemberjenniBrooklyn13-Dec-09 23:35 
GeneralRe: Explanation on "D3" PinmemberRascalRobot27-Jan-10 8:20 
GeneralLicense Pinmembercesarfricks20-Aug-09 9:07 
Questioncan some one send me the built executable? I am not able to build it :( Pinmembervikrampatwardhan26-Jan-09 19:08 
GeneralFaster GetBytes() [modified] PinmemberMark Jerde22-Jan-09 11:16 
GeneralRe: Faster GetBytes() PinmemberMember 334182311-Oct-09 18:20 
GeneralReally good Pinmemberankit_vyas2-Sep-08 15:50 
QuestionWhat about the speed and simplicity of my function ? [modified] Pinmembergaby_la_star12-Nov-07 1:05 
Generalthank u so much neilck ! Pinmemberbeginner_csharper15-Oct-07 1:25 
GeneralBitConverter PinmemberMihail Stefanov7-Jul-07 13:27 
GeneralSimpler, faster, better ... and most of all standard way PinmemberSébastien Ros14-May-07 5:36 
GeneralRe: Simpler, faster, better ... and most of all standard way PinmemberStefan Gheorghe3-Jul-07 13:23 
GeneralRe: Simpler, faster, better ... and most of all standard way PinmemberSebastien Ros11-Jul-07 0:31 
GeneralRe: Simpler, faster, better ... and most of all standard way [modified] PinmemberGeorge Helyar5-Apr-08 6:33 
GeneralRe: Simpler, faster, better ... and most of all standard way Pinmemberj@mars16-Apr-08 4:44 
GeneralRe: Simpler, faster, better ... and most of all standard way PinmemberGeorge Helyar16-Apr-08 5:33 
GeneralRe: Simpler, faster, better ... and most of all standard way Pinmemberj@mars16-Apr-08 6:20 
GeneralRe: Simpler, faster, better ... and most of all standard way PinmemberGeorge Helyar16-Apr-08 7:43 
GeneralRe: Simpler, faster, better ... and most of all standard way Pinmemberramaluciano30-Nov-08 9:12 
GeneralRe: Simpler, faster, better ... and most of all standard way Pinmemberbobslayer31-Jul-07 5:20 
GeneralPerfect PinmemberDavepow165-Mar-07 9:21 
NewsAnother fast variant of mine.... [modified] PinmemberRealFractalizeR4-Mar-07 9:32 
GeneralI think this is faster (tested) Pinmembermeraklideve25-Jun-08 3:40 
GeneralRe: I think this is faster (tested) PinmemberRealFractalizeR25-Jun-08 11:52 
Generalbig endian hex Pinmembervadivelkumar21-Feb-07 23:28 
GeneralBuilt in .NET parse function that does this PinmemberMGutman8-Jan-07 7:45 
GeneralRe: Built in .NET parse function that does this PinmembernoGuns19-Apr-07 10:43 
GeneralRe: Built in .NET parse function that does this PinmemberMr Marchepane7-May-07 9:10 
GeneralRe: Built in .NET parse function that does this PinmemberSimon Capewell22-Nov-07 3:29 
GeneralSaved me a bunch of time - thanks PinmemberTimBSmith19715-Jan-07 13:36 
Generalwonderful Pinmembersinan12345617-Oct-06 5:04 
General'.' being not properly converted PinmemberHoodwink13-Sep-06 12:20 
GeneralSimpler Pinmemberraytaller6-Jun-06 6:51 
GeneralRe: Simpler PinmemberMGutman8-Jan-07 7:49 
GeneralIT students Pinmembersunset_h22_m6-Apr-06 3:23 
GeneralSystem.Uri.IsHexDigit PinmemberChirpychips3-Dec-05 3:06 
GeneralThanks to all for performance tips Pinmemberneilck22-Jun-05 14:29 
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 

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