I have many immutable value type classes, for example EmailAddress
, which ensure any non null instance is valid. I would like to control the serialization of these types of objects to be just the standard string representation ("[email protected]"
) when persisted using MongoDB C# Driver.
I have tried implementing the IBsonSerilizer
however it will only allow for objects or arrays at the root level. I was able to implement proper Json Serilization with Json.NET, is there a different approach I should be taking?
I assume you mean an EmailAddress class something like this:
[BsonSerializer(typeof(EmailAddressSerializer))]
public class EmailAddress
{
private string _value;
public EmailAddress(string value)
{
_value = value;
}
public string Value
{
get { return _value; }
}
}
I've used an attribute to link the EmailAddress class to a custom serializer, which could be implemented like this:
public class EmailAddressSerializer : BsonBaseSerializer
{
public override object Deserialize(BsonReader bsonReader, Type nominalType, Type actualType, IBsonSerializationOptions options)
{
if (bsonReader.GetCurrentBsonType() == BsonType.Null)
{
bsonReader.ReadNull();
return null;
}
else
{
var value = bsonReader.ReadString();
return new EmailAddress(value);
}
}
public override void Serialize(BsonWriter bsonWriter, Type nominalType, object value, IBsonSerializationOptions options)
{
if (value == null)
{
bsonWriter.WriteNull();
}
else
{
var emailAddress = (EmailAddress)value;
bsonWriter.WriteString(emailAddress.Value);
}
}
}
You can't serialize an EmailAddress as the root document (because it's not a document...). But you could use an EmailAddress embedded in some other document. For example:
public class Person
{
public int Id { get; set; }
public EmailAddress EmailAddress { get; set; }
}
Which you could test using code like the following:
var person = new Person { Id = 1, EmailAddress = new EmailAddress("[email protected]") };
var json = person.ToJson();
var rehyrdated = BsonSerializer.Deserialize<Person>(json);
The resulting JSON/BSON document is:
{ "_id" : 1, "EmailAddress" : "[email protected]" }
After I read the answer of @Davide Icardi I found out there is built in convention to use immutable objects.
Just register the convention
ConventionRegistry.Register(nameof(ImmutableTypeClassMapConvention),
new ConventionPack { new ImmutableTypeClassMapConvention()}, type => true);
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