The System.Data namespace provides access to classes that represent the ADO.NET architecture. ADO.NET lets you build components that efficiently manage data from multiple data sources.

In a disconnected scenario such as the Internet, ADO.NET provides the tools to request, update, and reconcile data in multiple tier systems. The ADO.NET architecture is also implemented in client applications, such as Windows Forms, or HTML pages created by ASP.NET.

The centerpiece of the ADO.NET architecture is the DataSet class. Each DataSet can contain multiple DataTable objects, with each DataTable containing data from a single data source, such as SQL Server.

Each DataTable contains a DataColumnCollection--a collection of DataColumn objects--that determines the schema of each DataTable. The DataType property determines the type of data held by the DataColumn. The ReadOnly and AllowDBNull properties let you further guarantee data integrity. The Expression property lets you construct calculated columns.

If a DataTable participates in a parent/child relationship with another DataTable, the relationship is constructed by adding a DataRelation to the DataRelationCollection of a DataSet object. When such a relation is added, a UniqueConstraint and a ForeignKeyConstraint are both created automatically, depending on the parameter settings for the constructor. The UniqueConstraint guarantees that values that are contained in a column are unique. The ForeignKeyConstraint determines what action will happen to the child row or column when a primary key value is changed or deleted.

Using the System.Data.SqlClient namespace (the.NET Framework Data Provider for SQL Server), the System.Data.Odbc namespace (the.NET Framework Data Provider for ODBC), the System.Data.OleDb namespace (the.NET Framework Data Provider for OLE DB), or the System.Data.OracleClient namespace (the .NET Framework Data Provider for Oracle), you can access a data source to use together with a DataSet. Each.NET Framework data provider has a corresponding DataAdapter that you use as a bridge between a data source and a DataSet.

Classes

---

	Class	Description
	Constraint	Represents a constraint that can be enforced on one or more DataColumn objects.
	ConstraintCollection	Represents a collection of constraints for a DataTable.
	ConstraintException	Represents the exception that is thrown when attempting an action that violates a constraint.
	DataColumn	Represents the schema of a column in a DataTable.
	DataColumnChangeEventArgs	Provides data for the ColumnChanging event.
	DataColumnCollection	Represents a collection of DataColumn objects for a DataTable.
	DataException	Represents the exception that is thrown when errors are generated using ADO.NET components.
	DataRelation	Represents a parent/child relationship between two DataTable objects.
	DataRelationCollection	Represents the collection of DataRelation objects for this DataSet.
	DataRow	Represents a row of data in a DataTable.
	DataRowBuilder	The DataRowBuilder type supports the .NET Framework infrastructure and is not intended to be used directly from your code.
	DataRowChangeEventArgs	Provides data for the RowChanged, RowChanging, OnRowDeleting, and OnRowDeleted events.
	DataRowCollection	Represents a collection of rows for a DataTable.
	DataRowView	Represents a customized view of a DataRow.
	DataSet	Represents an in-memory cache of data.
	DataSetSchemaImporterExtension	This member supports the .NET Framework infrastructure and is not intended to be used directly from your code.
	DataSysDescriptionAttribute	Marks a property, event, or extender with a description. Visual designers can display this description when referencing the member.
	DataTable	Represents one table of in-memory data.
	DataTableClearEventArgs	Provides data for the Clear method.
	DataTableCollection	Represents the collection of tables for the DataSet.
	DataTableNewRowEventArgs	Provides data for the NewRow method.
	DataTableReader	The DataTableReader obtains the contents of one or more DataTable objects in the form of one or more read-only, forward-only result sets.
	DataView	Represents a databindable, customized view of a DataTable for sorting, filtering, searching, editing, and navigation.
	DataViewManager	Contains a default DataViewSettingCollection for each DataTable in a DataSet.
	DataViewSetting	Represents the default settings for ApplyDefaultSort, DataViewManager, RowFilter, RowStateFilter, Sort, and Table for DataViews created from the DataViewManager.
	DataViewSettingCollection	Contains a read-only collection of DataViewSetting objects for each DataTable in a DataSet.
	DBConcurrencyException	The exception that is thrown by the DataAdapter during an insert, update, or delete operation if the number of rows affected equals zero.
	DeletedRowInaccessibleException	Represents the exception that is thrown when an action is tried on a DataRow that has been deleted.
	DuplicateNameException	Represents the exception that is thrown when a duplicate database object name is encountered during an add operation in a DataSet -related object.
	EvaluateException	Represents the exception that is thrown when the Expression property of a DataColumn cannot be evaluated.
	FillErrorEventArgs	Provides data for the FillError event of a DbDataAdapter.
	ForeignKeyConstraint	Represents an action restriction enforced on a set of columns in a primary key/foreign key relationship when a value or row is either deleted or updated.
	InRowChangingEventException	Represents the exception that is thrown when you call the EndEdit method within the RowChanging event.
	InternalDataCollectionBase	Provides the base functionality for creating collections.
	InvalidConstraintException	Represents the exception that is thrown when incorrectly trying to create or access a relation.
	InvalidExpressionException	Represents the exception that is thrown when you try to add a DataColumn that contains an invalid Expression to a DataColumnCollection.
	MergeFailedEventArgs	Occurs when a target and source DataRow have the same primary key value, and the EnforceConstraints property is set to true.
	MissingPrimaryKeyException	Represents the exception that is thrown when you try to access a row in a table that has no primary key.
	NoNullAllowedException	Represents the exception that is thrown when you try to insert a null value into a column where AllowDBNull is set to false.
	OperationAbortedException	This exception is thrown when an ongoing operation is aborted by the user.
	PropertyCollection	Represents a collection of properties that can be added to DataColumn, DataSet, or DataTable.
	ReadOnlyException	Represents the exception that is thrown when you try to change the value of a read-only column.
	RowNotInTableException	Represents the exception that is thrown when you try to perform an operation on a DataRow that is not in a DataTable.
	StateChangeEventArgs	Provides data for the state change event of a .NET Framework data provider.
	StatementCompletedEventArgs	Provides additional information for the StatementCompleted event.
	StrongTypingException	The exception that is thrown by a strongly typed DataSet when the user accesses a DBNull value.
	SyntaxErrorException	Represents the exception that is thrown when the Expression property of a DataColumn contains a syntax error.
	TypedDataSetGenerator	Used to create a strongly typed DataSet.
	TypedDataSetGeneratorException	The exception that is thrown when a name conflict occurs while generating a strongly typed DataSet.
	UniqueConstraint	Represents a restriction on a set of columns in which all values must be unique.
	VersionNotFoundException	Represents the exception that is thrown when you try to return a version of a DataRow that has been deleted.

Interfaces

---

	Interface	Description
	IColumnMapping	Associates a data source column with a DataSet column, and is implemented by the DataColumnMapping class, which is used in common by .NET Framework data providers.
	IColumnMappingCollection	Contains a collection of DataColumnMapping objects, and is implemented by the DataColumnMappingCollection, which is used in common by .NET Framework data providers.
	IDataAdapter	Allows an object to implement a DataAdapter, and represents a set of methods and mapping action-related properties used to fill and refresh a DataSet and update a data source.
	IDataParameter	Represents a parameter to a Command object, and optionally, its mapping to DataSet columns; and is implemented by .NET Framework data providers that access data sources.
	IDataParameterCollection	Collects all parameters relevant to a Command object and their mappings to DataSet columns, and is implemented by .NET Framework data providers that access data sources.
	IDataReader	Provides a means of reading one or more forward-only streams of result sets obtained by executing a command at a data source, and is implemented by .NET Framework data providers that access relational databases.
	IDataRecord	Provides access to the column values within each row for a DataReader, and is implemented by .NET Framework data providers that access relational databases.
	IDbCommand	Represents an SQL statement that is executed while connected to a data source, and is implemented by .NET Framework data providers that access relational databases.
	IDbConnection	Represents an open connection to a data source, and is implemented by .NET Framework data providers that access relational databases.
	IDbDataAdapter	Represents a set of command-related properties that are used to fill the DataSet and update a data source, and is implemented by .NET Framework data providers that access relational databases.
	IDbDataParameter	Used by the Visual Basic .NET Data Designers to represent a parameter to a Command object, and optionally, its mapping to DataSet columns.
	IDbTransaction	Represents a transaction to be performed at a data source, and is implemented by .NET Framework data providers that access relational databases.
	ITableMapping	Associates a source table with a table in a DataSet, and is implemented by the DataTableMapping class, which is used in common by .NET Framework data providers.
	ITableMappingCollection	Contains a collection of TableMapping objects, and is implemented by the DataTableMappingCollection, which is used in common by .NET Framework data providers.

Delegates

---

	Delegate	Description
	DataColumnChangeEventHandler	Represents the method that will handle the ColumnChanging event.
	DataRowChangeEventHandler	Represents the method that will handle the RowChanging, RowChanged, RowDeleting, and RowDeleted events of a DataTable.
	DataTableClearEventHandler	Represents the method that handles the Clear method.
	DataTableNewRowEventHandler	Represents the method that handles the NewRow method.
	FillErrorEventHandler	Represents the method that will handle the FillError event.
	MergeFailedEventHandler	Represents the method that will handle the MergeFailed event.
	StateChangeEventHandler	Represents the method that will handle the StateChange event.
	StatementCompletedEventHandler	The delegate type for the event handlers of the StatementCompleted event.

Enumerations

---

	Enumeration	Description
	AcceptRejectRule	Determines the action that occurs when the AcceptChanges or RejectChanges method is invoked on a DataTable with a ForeignKeyConstraint.
	CommandBehavior	Provides a description of the results of the query and its effect on the database.
	CommandType	Specifies how a command string is interpreted.
	ConflictOption	Specifies how conflicting changes to the data source will be detected and resolved.
	ConnectionState	Describes the current state of the connection to a data source.
	DataRowAction	Describes an action performed on a DataRow.
	DataRowState	Gets the state of a DataRow object.
	DataRowVersion	Describes the version of a DataRow.
	DataSetDateTime	Describes the serialization format for DateTime columns in a DataSet.
	DataViewRowState	Describes the version of data in a DataRow.
	DbType	Specifies the data type of a field, a property, or a Parameter object of a .NET Framework data provider.
	IsolationLevel	Specifies the transaction locking behavior for the connection.
	KeyRestrictionBehavior	Identifies a list of connection string parameters identified by the KeyRestrictions property that are either allowed or not allowed.
	LoadOption	Controls how the values from the data source will be applied to existing rows when using the Load or Load method.
	MappingType	Specifies how a DataColumn is mapped.
	MissingMappingAction	Determines the action that occurs when a mapping is missing from a source table or a source column.
	MissingSchemaAction	Specifies the action to take when adding data to the DataSet and the required DataTable or DataColumn is missing.
	ParameterDirection	Specifies the type of a parameter within a query relative to the DataSet.
	PropertyAttributes	Specifies the attributes of a property.
	Rule	Indicates the action that occurs when a ForeignKeyConstraint is enforced.
	SchemaSerializationMode	Indicates the schema serialization mode for a typed DataSet.
	SchemaType	Specifies how to handle existing schema mappings when performing a FillSchema operation.
	SerializationFormat	Determines the serialization format for a DataSet.
	SqlDbType	Specifies SQL Server-specific data type of a field, property, for use in a SqlParameter.
	StatementType	Specifies the type of SQL query to be used by the OleDbRowUpdatedEventArgs, OleDbRowUpdatingEventArgs, SqlRowUpdatedEventArgs, or SqlRowUpdatingEventArgs class.
	UpdateRowSource	Specifies how query command results are applied to the row being updated.
	UpdateStatus	Specifies the action to take with regard to the current and remaining rows during an Update.
	XmlReadMode	Specifies how to read XML data and a relational schema into a DataSet.
	XmlWriteMode	Specifies how to write XML data and a relational schema from a DataSet.