The SqlDataAdapter Class

The SqlDataAdapter Class You use an object of the SqlDataAdapter class to synchronize data stored in a DataSet object with a SQL Server database.. Table 10.1: SqlDataAdapter PROPERTIES A

The SqlDataAdapter Class

You use an object of the SqlDataAdapter class to synchronize data stored in a DataSet object with a SQL Server database You use an object of the OleDbDataAdapter class to synchronize data with a database that supports OLE DB, such as Oracle or Access You use an object of the OdbcDataAdapter class to synchronize data with a database that supports ODBC

Note Although the SqlDataAdapter class is specific to SQL Server, many of the

properties and methods in this class are the same as those for the

OleDbDataAdapter and OdbcDataAdapter classes

Table 10.1 shows some of the SqlDataAdapter properties

Table 10.1: SqlDataAdapter PROPERTIES

AcceptChangesDuringF

ill

bool Gets or sets a bool that indicates

whether the AcceptChanges() method is called after a DataRow object has been added, modified,

or removed in a DataTable object The default is true

ContinueUpdateOnError bool Gets or sets a bool that indicates

whether to continue updating the database when an error occurs

When set to true, no exception is thrown when an error occurs during the update of a row The update of the row is skipped and the error information is placed in the RowError property of the DataRow that caused the error The DataAdapter continues to update subsequent rows

When set to false, an exception is thrown when an error occurs The default is false

DeleteCommand SqlCommand Gets or sets a command containing

Table 10.1: SqlDataAdapter PROPERTIES

a SQL DELETE statement or stored procedure call to remove rows from the database

InsertCommand SqlCommand Gets or sets a command containing

a SQL INSERT statement or stored procedure call to add rows

to the database

MissingMappingAction MissingMappingAction Gets or sets the action to take

when the incoming table or column doesn't have a matching table or column in the

TableMappings collection

The values for this action come from the

System.Data.MissingMappingActi

on enumeration with the members Error, Ignore, and Passthrough:

• Error means a

SystemException is thrown

• Ignore means the table or

column is ignored and not read

• Passthrough means the

table or column is added to the DataSet with its original name

The default is Passthrough

MissingSchemaAction MissingSchemaAction Gets or sets the action to take

when the incoming column doesn't have a matching column in the DataTable object's Column collection

The values for this action come from the

System.Data.MissingSchemaActio

Table 10.1: SqlDataAdapter PROPERTIES

n enumeration with the members Add, AddWithKey, Error, and Ignore:

• Add means the column is

added to the DataTable

• AddWithKey means the

column and primary key information is added to the DataTable

• Error means a

SystemException is thrown

• Ignore means the column is

ignored and not read

The default is Add

SelectCommand SqlCommand Gets or sets a command containing

a SQL SELECT statement or stored procedure call to retrieve rows from the database

TableMappings DataTableMappingCollecti

on

Gets a DataTableMappingCollection that contains the mapping between a database table and a DataTable object in the DataSet

UpdateCommand SqlCommand Gets or sets a command containing

a SQL UPDATE statement or stored procedure call to modify rows in the database

Table 10.2 shows some of the SqlDataAdapter methods

Table 10.2: SqlDataAdapter METHODS

Fill() int Overloaded Synchronizes the rows in the

DataSet object to match those in the database The int returned by this method is the number of rows synchronized in the DataSet with the

Table 10.2: SqlDataAdapter METHODS

database

FillSchema() DataTable

DataTable[]

Overloaded Adds a DataTable to a DataSet object and configures the schema to match the database

GetFillParameters() IDataParameter[] Returns an array of any parameters set for the

SQL SELECT statement

Update() int Overloaded Calls the respective SQL INSERT,

UPDATE, or DELETE statements or stored procedure call (stored in the InsertCommand, UpdateCommand, and DeleteCommand properties, respectively) for each row that has been added, modified, or removed from a DataTable object The int returned by this method

is the number of rows updated

Table 10.3 shows some of the SqlDataAdapter events

Table 10.3: SqlDataAdapter EVENTS

FillError FillErrorEventHandler Fires when an error occurs during a fill

operation

RowUpdating RowUpdatingEventHandler Fires before a row is added, modified, or

deleted in the database

RowUpdated RowUpdatedEventHandler Fires after a row is added, modified, or

deleted in the database

You'll learn how to use some of these properties and methods to store data in DataSet objects in this chapter You'll see how to use the other properties, methods, and the events

in Chapter 11, in which you'll learn how to modify data in DataSet objects, and then push those modifications to the database

Creating a SqlDataAdapter Object

You create a SqlDataAdapter object using one of the following SqlDataAdapter

constructors:

SqlDataAdapter()

SqlDataAdapter(SqlCommand mySqlCommand)

SqlDataAdapter(string selectCommandString, SqlConnection mySqlConnection)

SqlDataAdapter(string selectCommandString, string connectionString)

where

mySqlCommand specifies your SqlCommand object

selectCommandString specifies your SELECT statement or stored procedure call

mySqlConnection specifies your SqlConnection object

connectionString specifies your connection string to connect to the database

The following example uses the SqlDataAdapter() constructor to create a SqlDataAdapter object:

SqlDataAdapter mySqlDataAdapter = new SqlDataAdapter();

Before using mySqlDataAdapter to populate a DataSet, you must set its SelectCommand property to a SqlCommand that contains a SELECT command or stored procedure call The following example creates a SqlCommand object with its CommandText property set

to a SELECT statement that will retrieve the top five rows from the Products table, and sets the CommandText property of mySqlDataAdapter to that SqlCommand object:

SqlCommand mySqlCommand = mySqlConnection.CreateCommand();

mySqlCommand.CommandText =

"SELECT TOP 5 ProductID, ProductName, UnitPrice " +

"FROM Products " +

"ORDER BY ProductID";

mySqlDataAdapter.SelectCommand = mySqlCommand;

The next example uses the SqlDataAdapter(SqlCommand mySqlCommand) constructor:

SqlDataAdapter mySqlDataAdapter = new SqlDataAdapter(mySqlCommand);

The next example uses the SqlDataAdapter(string selectCommandString, SqlConnection mySqlConnection) constructor:

SqlConnection mySqlConnection =

new SqlConnection(

"server=localhost;database=Northwind;uid=sa;pwd=sa"

);

string selectCommandString =

"SELECT TOP 10 ProductID, ProductName, UnitPrice " +

"FROM Products " +

"ORDER BY ProductID";

SqlDataAdapter mySqlDataAdapter =

new SqlDataAdapter(selectCommandString, mySqlConnection);

The final example uses the SqlDataAdapter(string selectCommandString, string

connectionString) constructor:

string selectCommandString =

"server=localhost;database=Northwind;uid=sa;pwd=sa";

string connectionString =

"SELECT TOP 10 ProductID, ProductName, UnitPrice " +

"FROM Products " +

"ORDER BY ProductID";

SqlDataAdapter mySqlDataAdapter =

new SqlDataAdapter(selectCommandString, connectionString);

Warning This constructor causes the SqlDataAdapter object to create a separate

SqlConnection object This is typically undesirable from a performance

perspective because opening a connection to the database using a SqlConnection

object takes a relatively long time You should therefore avoid using the

SqlDataAdapter(string selectCommandString, string connectionString)

constructor Instead, you should use an existing SqlConnection object with your SqlDataAdapter object

A DataAdapter object doesn't store rows: it merely acts as a conduit between the database and an object of the DataSet class In the next section, you'll learn about the DataSet class