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DataAdapter.FillSchema Method

Adds a DataTable named "Table" to the specified DataSet and configures the schema to match that in the data source based on the specified SchemaType.

[Visual Basic]
Public MustOverride Function FillSchema( _
   ByVal dataSet As DataSet, _
   ByVal schemaType As SchemaType _
) As DataTable() Implements IDataAdapter.FillSchema
[C#]
public abstract DataTable[] FillSchema(
 DataSet dataSet,
 SchemaType schemaType
);
[C++]
public: virtual DataTable* FillSchema(
 DataSet* dataSet,
 SchemaType schemaType
) [] = 0;
[JScript]
public abstract function FillSchema(
   dataSet : DataSet,
 schemaType : SchemaType
) : DataTable[];

Parameters

dataSet
The DataSet to be filled with the schema from the data source.
schemaType
One of the SchemaType values.

Return Value

A DataTable object that contains schema information returned from the data source.

Implements

IDataAdapter.FillSchema

Remarks

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 the DataAdapter 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 should use caution when using column and table names to 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.

Note   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.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework

See Also

DataAdapter Class | DataAdapter Members | System.Data.Common Namespace | Fill

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