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This article mainly explains the "what is the role of the ADO.NET DataAdapter type", the content of the explanation is simple and clear, easy to learn and understand, the following please follow the editor's ideas slowly in depth, together to study and learn "what is the role of the ADO.NET DataAdapter type" bar!

The DataAdapter object acts as a bridge between the database and the non-connected objects in the ADO.NET object model. The Fill method of the DataAdapter object class provides an efficient mechanism for introducing query results into DataSet or DataTable so that data can be processed offline. You can also use the DataAdapter object to submit pending changes stored in the DataSet object to the database.

The ADO.NET DataAdapter class exposes a large number of properties, which are actually Command objects. For example, the SelectCommand property contains a Command object that represents the query that will be used to populate the DataSet object. The DataAdapter class also has properties such as UpdateCommand,InsertCommand and DeleteCommand, which correspond to Command objects that submit modified, new, or deleted rows to the database, respectively.

These Command objects provide updates that occur automatically in the Recordset objects of ADO and DAO. For example, when you run a query in ADO to generate a Recordset object, ADO's cursor engine asks the database about the metadata about the query to determine where the results come from. ADO then uses the metadata to establish update logic to convert changes in the Recordset object into changes in the database.

So why does the DataAdapter object of ADO.NET have separate UpdateCommand,InsertCommand and DeleteCommand properties? This is to allow developers to define their own update logic. Both ADO and DAO have limited update capabilities because both object models convert changes in Recordset into operational queries that directly reference tables in the database. In order to maintain the security and integrity of data, many database administrators restrict access to tables in their databases, so the way to change the contents of tables is to call stored procedures.

The ADO.NET DataAdapter class does not know how to use stored procedures to commit changes, nor does it provide a mechanism for developers to specify their own update logic. ADO.NET DataAdapter is fine.

With the DataAdapter object, you can set the UpdateCommand,InsertCommand and DeleteCommand properties to call stored procedures that modify, add, or delete rows of data for the corresponding tables in the database. You can then simply call the Update method of the DataAdapter object, and ADO.NET will use the created Command object to commit the cached changes in the DataSet to the database.

As mentioned earlier, the DataAdapter class populates the table in the DataSet object and can read cached changes and commit them to the database. The ADO.NET DataAdapter class has some supporting properties that can be used to track where and what happens. One of the attributes is the TableMappings collection, which is used to track which table in the database corresponds to which table in the DataSet object. Each table map has a similar attribute for mapping columns, called the ColumnMapping collection.

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