using System;

using MongoDB.Bson;  

using MongoDB.Bson.Serialization;  

using MongoDB.Bson.Serialization.Attributes;  

using MongoDB.Bson.Serialization.Serializers;  

using MongoDB.Driver;  

​

 public class EmptyStringAvoidingSerializer : SerializerBase<string>

{

    public override void Serialize(BsonSerializationContext context, BsonSerializationArgs args, string value)

    {

        // Serialize as null if the string is empty

        if (string.IsNullOrEmpty(value))

        {

            context.Writer.WriteNull();

        }

        else

        {

            context.Writer.WriteString(value);

        }

    }

​

    public override string Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)

    {

        // Deserialize the string, treating null as an empty string

        var value = context.Reader.ReadString();

        return value ?? string.Empty;

    }

}

​

public class Item  

{  

    [BsonId]  

    public ObjectId Id { get; set; }  

    public string Name { get; set; }  

    [BsonSerializer(typeof(EmptyStringAvoidingSerializer))]  

    public string Description { get; set; }  

}  

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        var newItem = new Item  

        {  

            Name = "Sample Item",  

            Description = ""  // Empty string  

        };  

        Console.WriteLine(newItem.ToJson());

    }

}

​

​