// Add the user.
User user = await graphClient.Users.Request().AddAsync(new User
{
    AccountEnabled = true,
    DisplayName = Resource.User + guid.Substring(0, 8),
    MailNickname = alias,
    PasswordProfile = new PasswordProfile
    {
        Password = Resource.Prop_Password
    },
    UserPrincipalName = alias + "@" + domain
});