Please help converting 2 PHP functions to vb.net (or c#)

[cicatrix]

I'm converting a php code containing the following 2 functions:

     /**
     * Covert a string into longinteger
     *
     * @param string $data
     * @return array
     */
    function _str2long($data)
    {
        $n = strlen($data);
        $tmp = unpack('N*', $data);
        $data_long = array();
        $j = 0;

        foreach ($tmp as $value) $data_long[$j++] = $value;
        return $data_long;
    }

    /**
     * Convert a longinteger into a string
     *
     * @param int $l
     * @return string
     */
    function _long2str($l)
    {
        return pack('N', $l);
    } 

I am currently concerned with php pack and unpack functions. Although I've got some rough understanding about what they are doing I am a bit worried if I understand them right and I've no test data to ensure I'll make a correct implementation. Can anyone help me to convert this code or basically, what I want is to get a correctly working implementation of php pack and upack functions with this exact format ("N" and "N*") in either vb.net or c#.