c# - DbReference with custom MongoIdentifier (MongoDB & NoRM) -

i'm new mongo user (haven't gotten used name even... makes me laugh every time), , have problem (feeling mongo).

i have class "user", mongoidentifier defined this:

[mongoidentifier]  public string username { get; set; }

in class "role" have dbreference looks this:

public dbreference<user> creator { get; set; }

this compiles well, when try set creator this:

role.creator = new norm.bson.dbtypes.dbreference<user>(useronline.username);

i following error:

system.formatexception: not find recognizable digits.

any ideas why?

thanks

found solution... had specify type of mongoidentifier:

public dbreference<user, string> creator { get; set; }

and...

role.creator = new norm.bson.dbtypes.dbreference<user, string>(useronline.username);

TY