How to generate HMAC-SHA1 in C#?

an extension to Vimvq1987's answer:

return hashValue.ToString(); doesn't produce the output you want/need. You have to convert the bytes in the array hashValue to their hex-string representation.
Can be as simple as return BitConverter.toString(hashValue); (prints upper-case letters A-F) or if you like it a bit more complex:

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Security.Cryptography;using System.IO;namespace ConsoleApplication1{    class Program    {        public static string Encode(string input, byte[] key)        {            HMACSHA1 myhmacsha1 = new HMACSHA1(key);            byte[] byteArray = Encoding.ASCII.GetBytes(input);            MemoryStream stream = new MemoryStream(byteArray);            return myhmacsha1.ComputeHash(stream).Aggregate("", (s, e) => s + String.Format("{0:x2}",e), s => s );        }        static void Main(string[] args)        {            byte[] key = Encoding.ASCII.GetBytes("abcdefghijklmnopqrstuvwxyz");            string input = "";            foreach (string s in new string[] { "Marry", " had", " a", " little", " lamb" })            {                input += s;                System.Console.WriteLine( Encode(input, key) );            }            return;        }    }}

which prints

3545e064fb59bc4bfc02b6e1c3d4925c898aa5043249f4c8468d4d67f465937da05b809eaff22fdb87baaadf5d096677f944015e53d283834eb1e9436325376820c29a09e3ab30db000033aa71d6927d54579b0146e2476595381d837ee38863be358213

and I get the exact same result for

<?php$secretKey = 'abcdefghijklmnopqrstuvwxyz';$signatureString = '';foreach( array('Marry',' had',' a',' little',' lamb') as $s ) {    $signatureString .= $s;    echo hash_hmac('sha1', $signatureString, $secretKey, false), "\n";}

edit: Dmitriy Nemykin suggested the following edit

public static string Encode(string input, byte[] key){    byte[] byteArray = Encoding.ASCII.GetBytes(input);    using(var myhmacsha1 = new HMACSHA1(key))    {        var hashArray = myhmacsha1.ComputeHash(byteArray);        return hashArray.Aggregate("", (s, e) => s + String.Format("{0:x2}",e), s => s );    }}

which was rejected. But as James already pointed out in a comment to this answer at the very least the using statement is a good point.

This site has some pretty good examples across languages: http://jokecamp.wordpress.com/2012/10/21/examples-of-creating-base64-hashes-using-hmac-sha256-in-different-languages/

The c# implementation at the time of writing is:

private string CreateToken(string message, string secret){ secret = secret ?? ""; var encoding = new System.Text.ASCIIEncoding(); byte[] keyByte = encoding.GetBytes(secret); byte[] messageBytes = encoding.GetBytes(message); using (var hmacsha256 = new HMACSHA256(keyByte)) { byte[] hashmessage = hmacsha256.ComputeHash(messageBytes); return Convert.ToBase64String(hashmessage); }}

Try this:

http://msdn.microsoft.com/en-us/library/system.security.cryptography.hmacsha1.aspx

quick and dirty code:

public string Encode(string input, byte [] key){        HMACSHA1 myhmacsha1 = new HMACSHA1(key);        byte[] byteArray = Encoding.ASCII.GetBytes( input );        MemoryStream stream = new MemoryStream( byteArray );         byte[] hashValue = myhmacsha1.ComputeHash(stream);        return hashValue.ToString();}