C# 4 and .NET 4

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Updating an existing row
Updating an existing row within the DataTable is just a case of using the DataRow class’s indexer with
either a column name or column number, as shown in the following code:
r["RegionDescription"]="North West England";
r[1] = "North West England";
Both of these statements are equivalent (in this example):
Changed RegionID 5 description
1 Eastern Unchanged
2 Western Unchanged
3 Northern Unchanged
4 Southern Unchanged
5 North West England Modified
Prior to updating the database, the row updated has its state set to Modified as shown.
Deleting a row
Deleting a row is a matter of calling the Delete() method:
r.Delete();
A deleted row has its row state set to Deleted, but you cannot read columns from the deleted DataRow
because they are no longer valid. When the adaptor’s Update() method is called, all deleted rows will use
the DeleteCommand, which in this instance executes the RegionDelete stored procedure.
Writing Xml output
As you have seen already, the DataSet class has great support for defining its schema in XML, and just as
you can read data from an XML document, you can also write data to an XML document.
The DataSet.WriteXml() method enables you to output various parts of the data stored within the
DataSet. You can elect to output just the data, or the data and the schema. The following code shows an
example of both for the Region example shown earlier:
ds.WriteXml(".\\WithoutSchema.xml");
ds.WriteXml(".\\WithSchema.xml", XmlWriteMode.WriteSchema);
The first file, WithoutSchema.xml, is shown here:
1
Eastern
2
Western
3
Northern
4
Southern
code download WithoutSchema.xml
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