我们在身份提供者中有一个OpenID连接，用于在UI上对ADB2C域中的AD用户进行身份验证。我们之前使用graph创建了带有临时密码的ADB2C用户。但现在我需要创建一个联合用户，该用户将能够使用AD凭据登录。我们还删除了注册流程，只留下登录，因为我们只想通过图表创建用户。我有以下代码：

var newUser = new User
{
    AccountEnabled = true,
    DisplayName = user.DisplayName,
    GivenName = user.FirstName,
    Surname = user.Surname,
    Mail = user.Email,
    MobilePhone = user.Telephone,
    PasswordProfile = new PasswordProfile
    {
        ForceChangePasswordNextSignIn = true,
        Password = PasswordGenerator.GeneratePassword(16),
    },
    Identities = new List<ObjectIdentity> 
    {
        new ObjectIdentity
        {
            SignInType = "federated",
            Issuer = "https://login.microsoftonline.com/<AD TENANT>/v2.0",
            IssuerAssignedId = "<USER'S OBJECT ID FROM AD>",
        }
    },
    AdditionalData = new Dictionary<string, object>
    {
        { "IsAdmin", user.IsAdmin },
    },
    CreationType = null
};

var res = await _graphClient.Users.PostAsync(newUser);

但当我点击“登录与AD”在UI上，并输入AD用户的凭据，我得到了以下错误：AADB2C99002: User does not exist. Please sign up before you can sign in.