c# mongodb convert between model and bson

To convert between a model and BSON in C# with MongoDB, you can use the `BsonDocument` class and the `BsonSerializer` class from the MongoDB C# driver.

To convert a model to BSON:

using MongoDB.Bson;
using MongoDB.Bson.Serialization;

public class Person
{
    public ObjectId Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
}

Person person = new Person { Name = "John", Age = 30 };
BsonDocument bsonDocument = person.ToBsonDocument();

To convert BSON to a model:

using MongoDB.Bson;
using MongoDB.Bson.Serialization;

BsonDocument bsonDocument = ... // retrieve the document from MongoDB
Person person = BsonSerializer.Deserialize<Person>(bsonDocument);

Note that you should replace the `...` with the code that retrieves the document from MongoDB.

If you need to convert a list of models to BSON, you can use `BsonArray` and `ToBsonDocumentArray`:

List<Person> people = new List<Person>
{
    new Person { Name = "John", Age = 30 },
    new Person { Name = "Jane", Age = 25 }
};
BsonArray bsonArray = new BsonArray(people.Select(x => x.ToBsonDocument()));
BsonDocument bsonDocument = new BsonDocument { { "people", bsonArray } };

And to convert BSON to a list of models:

BsonDocument bsonDocument = ... // retrieve the document from MongoDB
BsonArray bsonArray = bsonDocument["people"].AsBsonArray;
List<Person> people = bsonArray.Select(x => BsonSerializer.Deserialize<Person>(x.AsBsonDocument)).ToList();

Again, you should replace the `...` with the code that retrieves the document from MongoDB.