Explain what a diffgram is and its usage ?

Answer Posted / swapna

A DiffGram is an XML format that is used to identify
current and original versions of data elements. The DataSet
uses the DiffGram format to load and persist its contents,
and to serialize its contents for transport across a
network connection. When a DataSet is written as a
DiffGram, it populates the DiffGram with all the necessary
information to accurately recreate the contents, though not
the schema, of the DataSet, including column values from
both the Original and Current row versions, row error
information, and row order.
When sending and retrieving a DataSet from an XML Web
service, the DiffGram format is implicitly used.
Additionally, when loading the contents of a DataSet from
XML using the ReadXml method, or when writing the contents
of a DataSet in XML using the WriteXml method, you can
select that the contents be read or written as a DiffGram.
The DiffGram format is divided into three sections: the
current data, the original (or "before") data, and an
errors section, as shown in the following example.
<?xml version="1.0"?>
<diffgr:diffgram
xmlns:msdata="urn:schemas-microsoft-com:xml-msdata"
xmlns:diffgr="urn:schemas-microsoft-com:xml-
diffgram-v1"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<DataInstance>
</DataInstance>
<diffgr:before>
</diffgr:before>
<diffgr:errors>
</diffgr:errors>
</diffgr:diffgram>
The DiffGram format consists of the following blocks of
data:
<DataInstance>
The name of this element, DataInstance, is used for
explanation purposes in this documentation. A DataInstance
element represents a DataSet or a row of a DataTable.
Instead of DataInstance, the element would contain the name
of the DataSet or DataTable. This block of the DiffGram
format contains the current data, whether it has been
modified or not. An element, or row, that has been modified
is identified with the diffgr:hasChanges annotation.
<diffgr:before>
This block of the DiffGram format contains the original
version of a row. Elements in this block are matched to
elements in the DataInstance block using the diffgr:id
annotation.
<diffgr:errors>
This block of the DiffGram format contains error
information for a particular row in the DataInstance block.
Elements in this block are matched to elements in the
DataInstance block using the diffgr:id annotation.

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