| Managed providers allow ADO.NET to interact with any type of OleDB-compliant data source. These providers are used to move data into the DataSet and its related classes, and can be used independently to modify data as well. There are two managed providers: OleDB and SQL. The former deals with all OleDB-compliant data stores, whereas the latter deals only with SQL Server. In nearly all cases, classes in one provider correspond exactly to classes in the other; the only difference is the use of a prefix: OleDb and Sql. For instance, both providers have an class that provides lightweight access to data, respectively named OleDbDataReader and SqlDataReader. Because of the similarities of these two providers, only the OleDb managed provider is covered here. Where there are differences in the two, a note is made. OleDbCommand The OleDbCommand class represents a SQL statement to be made to a data source. Table C.13 lists the properties and methods of this class. Table C.13. Properties and Methods of the OleDbCommand Class | Property | Description | | CommandText | The SQL statement to execute. | | CommandTimeout | The time limit in which the command must execute before termination. | | CommandType | Specifies how the CommandText property is interpreted. Can be StoredProcedure, TableDirect, or Text (default). | | Connection | Specifies an OleDbConnection used by this object. | | DesignTimeVisible | Indicates if the command object should be visible in a custom Windows Forms designer control. | | Parameters | Gets an OleDbParameterCollection object representing the parameters for use with this command. | | Transaction | The OleDbTransaction used by the command. | | UpdatedRowSource | The number of records affected by the command. Typically one if the command succeeds, and less than one otherwise. | | Method | Description | | Cancel | Cancels the execution of the command. | | CreateParameter | Creates an OleDbParameter for use with this command. | | ExecuteNonQuery | Executes a SQL statement that doesn't return any data. | | ExecuteReader | Returns an OleDbDataReader filled with the data returned from the command. | | ExecuteScalar | Executes the query, and returns value in the first column and first row of the returned results. | | Prepare | Creates a compiled version of the command. | | ResetCommandTimeout | Resets the CommandTimeout property to the default value. | OleDbCommandBuilder The OleDbCommandBuilder class represents an easy way to generate commands for use against a data source. Table C.14 lists the properties and methods of this class. Table C.14. Properties and Methods of the OleDbCommandBuilder Class | Property | Description | | DataAdapter | The name of an OleDbDataAdapter for which the commands are generated. | | QuotePrefix | Specifies a prefix to use when specifying data source object names (such as tbl for tables, sp for stored procedures, and so forth). | | QuoteSuffix | Specifies a suffix to use when specifying data source object names. | | Method | Description | | DeriveParameters | Fills the OleDbCommand's Parameters collection with values specified in the stored procedure. | | GetDeleteCommand | Gets the automatically generated SQL statement to delete rows from the data source. | | GetInsertCommand | Gets the automatically generated SQL statement to insert rows into the data source. | | GetUpdateCommand | Gets the automatically generated SQL statement to update rows in the data source. | | RefreshSchema | Retrieves the schema of the data source. | OleDbConnection The OleDbConnection class represents a connection to a data source. Table C.15 lists the properties, methods, and events of this class. Table C.15. Properties, Methods, and Events of the OleDbConnection Class | Property | Description | | ConnectionString | The string used to open a database. | | ConnectionTimeout | The time limit for establishing a connection to the database, after which an error will be generated. | | Database | The name of the database to use once the connection is established. | | DataSource | The name of the database to connect to. | | Provider | The name of the database provider. | | ServerVersion | A string containing the version of the server to which the client is connected. | | State | The current state of the connection. | | Method | Description | | BeginTransaction | Begins a database transaction. This method is overloaded. | | ChangeDatabase | Changes the current database to another specified value. | | Close | Closes the database connection. | | CreateCommand | Returns an OleDbCommand object to execute commands against the database. | | GetOleDbSchemaTable | Returns schema information from a data source specified by a GUID. (This method does not exist in the corresponding SqlConnection class.) | | Open | Attempts to open the connection to the database. | | ReleaseObjectPool | Indicates that the OleDbConnection object pooling can be cleared when the last underlying OLE DB provider is released. | | Event | Description | | InfoMessage | Occurs when the provider sends a message. Uses an OleDbInfoMessageEventArgs object for the event parameter. This object contains the following properties: ErrorCode An HRESULT value indicating the standard error. Errors An OleDbErrorCollection of warnings sent by the provider. Message The full text of the error message sent from the provider. Source The name of the object that generated the error. | | StateChange | Occurs when the state of the connection changes. Uses a StateChangeEventArgs for the event parameter. This object contains the following properties: CurrentState The new state of the connection. OriginalState The original state of the connection. | OleDbDataAdapter The OleDbDataAdapter class represents a set of data commands and a database connection that are used to fill a DataSet. Table C.16 lists the properties, methods, and events of this class. Table C.16. Properties, Methods, and Events of the OleDbDataAdapter Class | Property | Description | | DeleteCommand | Returns an OleDbCommand object that contains a SQL statement for deleting data from the DataSet. | | InsertCommand | Returns an OleDbCommand object that contains a SQL statement for inserting data into the DataSet. | | SelectCommand | Returns an OleDbCommand object that contains a SQL statement for selecting data from the DataSet. | | UpdateCommand | Returns an OleDbCommand object that contains a SQL statement for updating data in the DataSet. | | Method | Description | | Fill | Adds or changes rows in a DataSet to match the data source. This method is overloaded. | | FillSchema | Adds a DataTable to the specified DataSet and configures the schema of the table. This method is overloaded. | | GetFillParameters | Returns an array of IDataParameter objects that are used with the SELECT command. | | Update | Updates the data source with the information in the DataSet using the Delete, Insert, and UpdateCommand properties. This method is overloaded. | | FillError | Occurs when an error is returned during a Fill operation. Uses a FillErrorEventArgs object for the event parameter. This object contains the following properties: Continue Indicates if the operation should continue. DataTable The DataTable being updated when the error occurred. Errors Returns an Exception object representing the errors being handled. Values Returns an object representing the values for the row being updated when the error occurred. | | RowUpdated | Occurs after an Update command has executed. Uses an OleDbRowUpdatedEventArgs object for the event parameter. This object contains the following properties: Command Returns the OleDbCommand executed when Update is called. Errors Returns an Exception object representing the errors that occurred. RecordsAffected The number of records affected. Row Gets the DataRow used by Update. StatementType The type of SQL statement being executed. Status An UpdateStatus object representing the status of the command. TableMapping Gets the DataTableMapping sent with the Update command. | | RowUpdating | Occurs before an Update command has executed. Uses an OleDbRowUpdatingEventArgs object for the event parameter. This object contains the following properties: Command Returns the OleDbCommand to execute when Update is called. Errors Returns an Exception object representing the errors that occurred. Row Gets the DataRow used by Update. StatementType The type of SQL statement to execute. Status An UpdateStatus object representing the status of the command. TableMapping Gets the DataTableMapping sent with the Update command. | OleDbDataReader The OleDbDataReader class represents a lightweight, streaming method for retrieving data from a data source. It is similar to a DataSet, but provides less functionality with increased performance. Table C.17 lists the properties and methods of this class. Table C.17. Properties and Methods of the OleDbDataReader Class | Property | Description | | Depth | The depth of the reader. | | FieldCount | The number of fields within the current record. | | IsClosed | Indicates if the data reader is closed. | | Item | The value at the specified column in its native format. This method is overloaded. | | RecordsAffected | The number of records affected by the command. Typically, this is one if successful, less than one otherwise. | | Method | Description | | Close | Closes the OleDbDataReader object. | | GetBoolean | Returns the value at the column specified as a Boolean value. | | GetByte | Returns the value at the column specified as a Byte value. | | GetBytes | Returns the value at the column specified as a Byte array. | | GetChar | Returns the value at the column specified as a Char value. | | GetChars | Returns the value at the column specified as a Char array. | | GetDataTypeName | Returns the data type of the column specified. | | GetDateTime | Returns the value at the column specified as a DateTime value. | | GetDecimal | Returns the value at the column specified as a Decimal value. | | GetDouble | Returns the value at the column specified as a Double value. | | GetFieldType | Gets the Type that is the data type of the object. | | GetFloat | Returns the value at the column specified as a Float value. | | GetGuid | Returns the value at the column specified as a globally unique identifier value. | | GetInt16 | Returns the value at the column specified as a 16-bit signed integer. | | GetInt32 | Returns the value at the column specified as a 32-bit signed integer. | | GetInt64 | Returns the value at the column specified as a 64-bit signed integer. | | GetName | Returns the name of the column specified. | | GetOrdinal | Gets the column's index, given the column name. | | GetSchemaTable | Returns a DataTable object that describes the column metadata for this object. | | GetString | Returns the value at the column specified as a String value. | | GetTimeSpan | Returns the value at the column specified as a TimeSpan value. | | GetValue | Returns the value at the column specified in its native format. | | GetValues | Returns all of the attributes for the current record, and places them in a specified array. | | IsDBNull | Used to indicate nonexistent values. | | NextResult | Advances the reader to the next result, when reading from the results of batch SQL statements. | | Read | Moves the reader to the next record. | OleDbError and OleDbErrorCollection The OleDbError class collects information about a warning supplied from the data source. Table C.18 lists the properties of this class. Table C.18. Properties of the OleDbError Class | Property | Description | | Message | A short description of the error. | | NativeError | The database-specific error information. | | Source | Gets the object that generated the error. | | SQLState | Retrieves the five-character standard error code for the database. | Table C.19 lists the properties and method of the OleDbErrorCollection class, which represents a collection of OleDbError objects. Table C.19. Properties and Method of the OleDbErrorCollection OClass | Property | Description | | Count | The number of errors in the collection. | | Item | Gets an OleDbError in the collection with the specified index. | | Method | Description | | CopyTo | Copies the entire collection to an array, starting at the specified index. | OleDbParameter and OleDbParameterCollection The OleDbParameter class represents a value that is passed along with a database command to provide additional information or options. Table C.20 lists the properties and method of this class. Table C.20. Properties and Method of the OleDbParameter Class | Property | Description | | DbType | The data type of the data source. | | Direction | Indicates how the parameter will be used. Can be: Input, InputOutput, Output, or ReturnValue. | | IsNullable | Indicates if the parameter is allowed to contain a null value. | | OleDbType | Specifies the Type of this parameter. (This property does not exist in the corresponding SqlParameter class.) | | Offset | The offset to the Value property. (This property only exists in the SqlParameter class.) | | ParameterName | The name of the parameter. | | Precision | The maximum number of digits used to represent the parameter. | | Scale | The number of decimal places used to represent the parameter. | | Size | The maximum size of this parameter. | | SourceColumn | The name of the column in the data source mapped to the DataSet used for returning Value. | | SourceVersion | Specifies the row version to use when loading data. | | Value | The value of the parameter. | | Method | Description | | ToString | Returns the ParameterName. | Table C.21 lists the properties and methods of the OleDbParameterCollection class, which represents a collection of OleDbParameter objects. Table C.21. Properties and Methods of the OleDbParameterCollection Class | Property | Description | | Count | The number of OleDbParameter objects in the collection. | | Item | Gets an OleDbParameter in the collection with either the name of the parameter or its index in the collection. | | Method | Description | | Add | Adds a parameter to the collection. This method is overloaded. | | Clear | Clears the collection of all OleDbParameter objects. | | Contains | Indicates if the OleDbParameter with the specified name exists in the collection. | | CopyTo | Copies the entire collection to a specified array, starting at the specified index. | | IndexOf | Retrieves the index of the specified parameter. This method is overloaded. | | Insert | Inserts an OleDbParameter object at the specified index. | | Remove | Removes the specified parameter from the collection. This method is overloaded. | | RemoveAt | Removes the OleDbParameter at the specified index. | OleDbTransaction The OleDbTransaction class represents a transaction that occurs at the data source. Table C.22 lists the properties and methods of this class. Table C.22. Properties and Methods of the OleDbTransaction Class | Property | Description | | Connection | The OleDbConnection object associated with this transaction. | | IsoloationLevel | The isolation level for this transaction. Can be Chaos, ReadCommitted (default), ReadUncommitted, RepeatableRead, Serializable, or Unspecified. | | Methods | Description | | Begin | Starts the transaction. Subsequent commands and changes will all be stored in a transaction log pending committal, and can be rolled back at any time. | | Commit | Commits all changes since calling Begin. | | RollBack | Rolls back all changes that have been made to the data source since the Begin or Commit methods were called. | |
