[Umbraco] Add User with hashed password & check unique loginname

protected static bool addUmbracoUser(string loginName, string userName, string password)
{
    if (ensureUniqueLoginName(account))
    {
        User u = umbraco.BusinessLogic.User.MakeNew(userName, loginName.Trim(), hashPassword(password), new List < UserType> ());
        u.addApplication("content");
        u.addApplication("media");
        u.addApplication("users");
        u.addApplication("settings");
        u.addApplication("developer");
        u.addApplication("members");
        u.Save();
        return true;
    }
    else
    { return false; }
}

private static bool ensureUniqueLoginName(string loginName)
{
    umbraco.BusinessLogic.User[] u = umbraco.BusinessLogic.User.getAllByLoginName(loginName);
    if (u.Length != 0)
    {
        return false;
    }
    return true;
}

private static string hashPassword(string password)
{
    HMACSHA1 hash = new HMACSHA1();
    hash.Key = Encoding.Unicode.GetBytes(password);

    string encodedPassword = Convert.ToBase64String(hash.ComputeHash(Encoding.Unicode.GetBytes(password)));
    return encodedPassword;
}

Reference: http://our.umbraco.org/wiki/reference/api-cheatsheet/users,-user-types-and-permissions/add-user-with-hashed-password