Get BsonId before inserting to database ASP.NET

Question

I'm working on a custom attribute that i need to build from the _Id generated by Mongo.

Is there a way to do it before inserting the document ?

My C# Source - Model Class EmployeeModel

public class EmployeeModel
{
    
            [BsonId]
            [BsonRepresentation(BsonType.ObjectId)]
            public string Id { get; set; }
    
           
            [BsonElement("build_obj")]
            [JsonProperty("build_obj")]
            public string UrlBuild { get; set; }

}

What I want to achieve

{
    "_id" : ObjectId("575845a713d284da0ac2ee81"),
    "build_obj" : "thisIsanExample.com/575845a713d284da0ac2ee81",
}

{
    "_id" : ObjectId("575845d213d284da0ac2ee82"),
    "build_obj" : "thisIsanExample.com/575845a713d284da0ac2ee81,
}

Here's the service

    private static IMongoClient _client;
    private static IMongoDatabase _database;
    
    _client = new MongoClient();
    _database = _client.GetDatabase("RMS");
    var collection = _database.GetCollection<EmployeeModel>("Employee");
    
  public Employee Create(Employee emp)
        {
emp.build_obj = "thisIsanExample.com/" + emp.Id
  _employees.InsertOne(emp);
}

But couldn't manage to do it, Kindly assist me how to fetch the Id before insert on database ?