The SADataAdapter retrieves a result set into a DataTable. A DataSet is a collection of tables (DataTables) and the relationships and constraints between those tables. The DataSet is built into the .NET Framework, and is independent of the Data Provider used to connect to your database.
When you use the SADataAdapter, you must be connected to the database to fill a DataTable and to update the database with changes made to the DataTable. However, once the DataTable is filled, you can modify the DataTable while disconnected from the database.
If you do not want to apply your changes to the database right away, you can write the DataSet, including the data and/or the schema, to an XML file using the WriteXml method. Then, you can apply the changes at a later time by loading a DataSet with the ReadXml method. The following shows two examples.
ds.WriteXml("Employees.xml"); ds.WriteXml("EmployeesWithSchema.xml", XmlWriteMode.WriteSchema);
For more information, see the .NET Framework documentation for WriteXml and ReadXml.
When you call the Update method to apply changes from the DataSet to the database, the SADataAdapter analyzes the changes that have been made and then invokes the appropriate statements, INSERT, UPDATE, or DELETE, as necessary. When you use the DataSet, you can only make changes (inserts, updates, or deletes) to data that is from a single table. You cannot update result sets that are based on joins. If another user has a lock on the row you are trying to update, an exception is thrown.
Any changes you make to the DataSet are made while you are disconnected. This means that your application does not have locks on these rows in the database. Your application must be designed to resolve any conflicts that may occur when changes from the DataSet are applied to the database if another user changes the data you are modifying before your changes are applied to the database.
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