I spent a good portion of time last week working on serialization. During that time I found many examples utilizing either the BinaryFormatter or XmlSerializer. Unfortunately, what I did not find were any examples comprehensively detailing the differences between the two.
The genesis of my curiosity lies in why the BinaryFormatter is able to deserialize directly to an interface whilst the XmlSerializer is not. Jon Skeet in an answer to “casting to multiple (unknown types) at runtime” provides an example of direct binary serialization to an interface. Stan R. provided me with the means of accomplishing my goal using the XmlSerializer in his answer to “XML Object Deserialization to Interface.”
Beyond the obvious of the BinaryFormatter utilizes binary serialization whilst the XmlSerializer uses XML I’d like to more fully understand the fundamental differences. When to use one or the other and the pros and cons of each.
The reason a binary formatter is able to deserialize directly to an interface type is because when an object is originally serialized to a binary stream metadata containing type and assembly information is stuck in with the object data. This means that when the binary formatter deserializes the object it knows its type, builds the correct object and you can then cast that to an interface type that object implements.
The XML serializer on the otherhand just serializes to a schema and only serializes the public fields and values of the object and no type information other then that (e.g. interfaces the type implements).
Here is a good post, .NET Serialization, comparing the BinaryFormatter, SoapFormatter, and XmlSerializer. I recommend you look at the following table which in addition to the previously mentioned serializers includes the DataContractSerializer, NetDataContractSerializer and protobuf-net.