How can I tell the MongoDB C# driver to store all Guids in string format?

Question

I\'m currently applying the [BsonRepresentation(BsonType.String)] attribute to all Guid properties in my domain models to have those properties ser

Answer 1

While using conventions will work, pay attention to two important (and related) points:

1. The filter parameter is required, and if the filter is too general (for example: t => true), it can overwrite other registered conventions.
2. Be aware that the order of registered conventions is important, first register specific filters and after register general conventions.

Another option is to create a BSON Class Map for type Guid, which sets the representation to string:

if (!BsonClassMap.IsClassMapRegistered(typeof(Guid))) {
    BsonClassMap.RegisterClassMap(cm => {
        cm.AutoMap();
        cm.Conventions.SetSerializationOptionsConvention(new  TypeRepresentationSerializationOptionsConvention(typeof(Guid), BsonType.String));
    });
}

This should be done before any reading/writing using BsonSerializer, otherwise the default Class Map will be created, and you wont be able to change the Class Map.