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DbDataAdapter.FillSchema Method (DataTable, SchemaType, IDbCommand, CommandBehavior)

Configures the schema of the specified DataTable based on the specified SchemaType, command string, and CommandBehavior values.

Namespace:  System.Data.Common
Assembly:  System.Data (in System.Data.dll)

abstract FillSchema : 
        dataTable:DataTable * 
        schemaType:SchemaType * 
        command:IDbCommand * 
        behavior:CommandBehavior -> DataTable 
override FillSchema : 
        dataTable:DataTable * 
        schemaType:SchemaType * 
        command:IDbCommand * 
        behavior:CommandBehavior -> DataTable 

Parameters

dataTable
Type: System.Data.DataTable
The DataTable to be filled with the schema from the data source.
schemaType
Type: System.Data.SchemaType
One of the SchemaType values.
command
Type: System.Data.IDbCommand
The SQL SELECT statement used to retrieve rows from the data source.
behavior
Type: System.Data.CommandBehavior
One of the CommandBehavior values.

Return Value

Type: System.Data.DataTable
A of DataTable object that contains schema information returned from the data source.

The FillSchema method retrieves the schema from the data source using the SelectCommand. The connection object associated with the SelectCommand must be valid, but it does not need to be open. If the connection is closed before FillSchema is called, it is opened to retrieve data, then closed. If the connection is open before FillSchema is called, it remains open.

A FillSchema operation adds a DataTable to the destination DataSet. It then adds columns to the DataColumnCollection of the DataTable, and configures the following DataColumn properties if they exist at the data source:

FillSchema also configures the PrimaryKey and Constraints properties according to the following rules:

  • If one or more primary key columns are returned by the SelectCommand, they are used as the primary key columns for the DataTable.

  • If no primary key columns are returned but unique columns are, the unique columns are used as the primary key if, and only if, all the unique columns are nonnullable. If any of the columns are nullable, a UniqueConstraint is added to the ConstraintCollection, but the PrimaryKey property is not set.

  • If both primary key columns and unique columns are returned, the primary key columns are used as the primary key columns for the DataTable.

Note that primary keys and unique constraints are added to the ConstraintCollection according to the preceding rules, but other constraint types are not added.

If a unique clustered index is defined on a column or columns in a SQL Server table and the primary key constraint is defined on a separate set of columns, then the names of the columns in the clustered index will be returned. To return the name or names of the primary key columns, use a query hint with the SELECT statement that specifies the name of the primary key index. For more information about specifying query hints, see Query Hint (Transact-SQL).

If the IDataAdapter encounters duplicate columns while populating a DataTable, it generates names for the subsequent columns, using the pattern "columnname1", "columnname2", "columnname3", and so on. If the incoming data contains unnamed columns, they are placed in the DataSet according to the pattern "Column1", "Column2", and so on. When multiple result sets are added to the DataSet each result set is placed in a separate table. Additional result sets are named by appending integral values to the specified table name (for example, "Table", "Table1", "Table2", and so on.). Applications using column and table names should ensure that conflicts with these naming patterns does not occur.

FillSchema does not return any rows. Use the Fill method to add rows to a DataTable.

NoteNote

When handling batch SQL statements that return multiple results, the implementation of FillSchema for the .NET Framework Data Provider for OLE DB retrieves schema information for only the first result. To retrieve schema information for multiple results, use Fill with the MissingSchemaAction set to AddWithKey.

When using FillSchema, the .NET Framework Data Provider for SQL Server appends a FOR BROWSE clause to the statement being executed. The user should be aware of potential side effects, such as interference with the use of SET FMTONLY ON statements. See SQL Server Books Online for more information.

Notes to Implementers

This implementation of the FillSchema method is protected and is designed for use by a .NET Framework data provider.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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