[isf-wifidog] Password hash in C#

[Peter]

passwordHash($password) {
       //    /**
       //     * utf8_decode is used for backward compatibility with old 
passwords
       //     * containing special characters.
       //     * Conversion from UTF-8 to ISO-8859-1 is done to match the 
MD5 hash
       //     */
       return base64_encode(pack("H*", md5(utf8_decode($password))));

This is the php function that Wifidog uses. Ive tried to translate it to 
C# but I'm not getting the same output for the same inputs.

Has anyone done this in .NET?