C# Firestore クラスでデータ追加

[FirestoreData]
public class FSData
{
    [FirestoreProperty]
    public Timestamp AccessDate { get; set; }
    [FirestoreProperty]
    public double IdNumber { get; set; }
    [FirestoreProperty]
    public string Name { get; set; }
}
 

FSData fSData = new FSData
{
    AccessDate = Timestamp.GetCurrentTimestamp(),
    IdNumber = DateTime.Now.Millisecond,
    Name = "TEST 03"
};
;
string documentName = DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss");
Google.Cloud.Firestore.DocumentReference docRef = db.Collection("users").Document(documentName);
await docRef.SetAsync(fSData);