What is DiffGram?
ADO.NET introduced the DataSet class to support the disconnected, distributed data-access scenarios. With DataSet, the data retrieved from the database is cached in-memory, in addition to the constraints and relationships among the tables. When the ADO.NET DataSet is serialized as XML (for example, when returning a DataSet from an ASP.NET XML Web service method), the XML format used for DataSet serialization is known as DiffGram. Like Updategrams, DiffGrams also contains the tags that specify the original and new state of data. SQLXML and .NET Managed classes can be used to execute DiffGrams to perform the database updates, however there are many things that are supported by Updategrams and not by DiffGrams (ability to pass parameters being one example).