One of the biggest cribs about the DataSet in .NET 1.0 and 1.1 was its serialization performance. The DataSet, albeit providing a rich object model to work with data in a disconnected way, was a bane when it came to passing it across tiers of the application, typically in a remoting scenario. It turned out that in this scenario, the DataSet serialization glutted on bandwidth, memory and CPU cycles. Developers who were hell bent on using the DataSet eventually became the undisputed champions of object serialization, using wonky ways to serialize the dataset in an effort to make it optimal. Less nerdy developers adopted not so adventurous means like using custom collections and arrays, but sacrificing the high-fidelity object model of the DataSet in the process.
Someone said that every complex problem has a simple solution, and .NET 2.0 is turning out to be an angel to this end. As you might have already guessed, the voice from the sky is in form of a new property of the DataSet (and surprise, DataTable too) called RemotingFormat, which is an enumeration of type SerializationFormat having two members – Binary and Xml. Quite obviously, the default is Xml, to preserve backward compatibility.
Okay, I am digressing slightly here to note something interesting. The name of the property in discussion is RemotingFormat, not something like SerializationFormat or SerializedAs. I suppose, it is to enunciate two things:
DataSets (and now, even DataTable) implements IXmlSerializable, which is what the XmlSerializer looks for when serializing objects in the web service scenario. So, setting the RemotingFormat property there would be of no consequence, and it does not make sense there either.
Perhaps, DataSets are more apt for remoting scenarios, as compared to that of Web Services. This is not to say DataSets are deemed not usable in web services (as the implementation of IXmlSerializable would clarify). It is just that all the performance issues discussed earlier in this post would still apply in this case.
Finally, I would urge you to read this excellent article by Dino Esposito to get a better insight into this new feature and other improvements that have been added to the DataTable class as well.