C# Password Generator

Simple, yet very effective password generator which i use for new users registration.

public static string Generate(int passwordLength)
{
    string _allowedChars = "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNOPQRSTUVWXYZ0123456789_";
     
    Byte[] randomBytes = new Byte[passwordLength];
    Random rGen = new Random();
    rGen.NextBytes(randomBytes);

    char[] chars = new char[passwordLength];
    int allowedCharCount = _allowedChars.Length;

    for (int i = 0; i < passwordLength; i++)
    {
        chars[i] = _allowedChars[(int)randomBytes[i] % allowedCharCount];
    }

    return new string(chars);
}