TableMappings
DataTableMappingCollection dtmc = DataAdapter.TableMappings;
Accesses a collection of DataTableMapping objects
that map the data source table names to DataSet
table names. This allows different table names to be used during
change reconciliation. An empty collection is returned if no mappings
exist.
The following example shows how to set up a
TableMapping and a
ColumnMapping:
SqlDataAdapter da;
// ... code to set up the data adapter
// map the DataSet table MyOrders to the data source table Orders
DataTableMapping dtm = da.TableMappings.Add("Orders", "MyOrders");
// map the DataSet column MyOrderID (in the DataSet MyOrders table)
// to the data source column OrderID (in the data source Orders table)
dtm.ColumnMappings.Add("MyOrderID", "OrderID");The DataTableMappingCollection and
DataColumnMappingCollection collections have an
AddRange( ) method that allows an array of
mappings to be added in a single statement, as shown in the following
example:
// map the CustomerID and EmployeeID columns from the data source
dtm.ColumnMappings.AddRange(new DataColumnMapping[] {
new DataColumnMapping("MyCustomerID", "CustomerID"),
new DataColumnMapping("MyEmployeeID", "EmployeeID")});Mappings can be removed from both the
DataTableMappingCollection and
DataColumnMappingCollection objects using the
Remove( ), RemoveAt( ), or
Clear( ) methods. The following example
demonstrates using these methods with the
DataTableMappingCollection; using the methods with
the DataColumnMappingCollection is similar.
SqlDataAdapter da;
// ... code to set up the DataAdapter da
// map the DataSet table MyOrders to the data source table Orders
DataTableMapping dtm = da.TableMappings.Add("Orders", "MyOrders");
// The next three commands remove the mapping just added
// remove the table mapping just added, using a reference to the
// DataTableMapping object
da.TableMappings.Remove(dtm);
// use RemoveAt to remove the DataTableMapping s
da.TableMappings.RemoveAt(0);
// use RemoveAt with the data source table name
da.TableMappings.RemoveAt("Orders");
// use Clear method to remove all mappings
da.TableMappings.Clear();A mapping is created by adding a DataTableMapping
object to the DataTableMappingCollection
collection. This maps a table in the data source to a table with
different name in the DataSet.
Each DataTableMapping object contains a
DataColumnMappingCollection object that is
accessed through its ColumnMappings property. The
collection controls how columns in the data source are mapped to
DataColumn objects in the
DataTable. The column mapping applies only for the
table mapped by the DataTableMapping. A column
mapping is created by adding a DataColumnMapping
object to the DataColumnMappingCollection
collection. This maps a column in the data source to a column with a
different name in the DataSet.
Both table and column mappings can be used by the Fill( ) and FillSchema( ) methods when
retrieving data, and by the Update( ) method when
submitting DataSet changes back to the data
source. The Fill( ) method always uses mapping
information if it’s available; the
FillSchema( ) method lets you choose whether to
use the mapping information.
If incoming data source table and column names don’t
match DataSet object names, and mapping
isn’t performed, the
MissingMappingAction property of the
DataAdapter determines what action is taken when
data is retrieved using the Fill( ) method.
Similarly, if incoming data source table and column names
don’t match DataSet object names,
and mapping isn’t performed, the
MissingSchemaAction property of the data adapter
determines what action is taken when the schema is retrieved using
the FillSchema( ) or Fill( )
method.
The commonly used public properties of the
DataTableMappingCollection are listed and
described in Table 29-8.
The commonly used public methods of the
DataTableMappingCollection are listed and
described in Table 29-9.
The commonly used public properties of the
DataTableMapping class are listed and described in
Table 29-10.
The commonly used public methods of the
DataTableMapping class are listed and described in
Table 29-11.
The DataColumnMappingCollection is returned by the
ColumnMappings collection property of the
TableMappings class. It maps the names of columns
in the DataSet to columns in the data source with
different names.
The commonly used public properties of the
DataColumnMappingCollection are listed and
described in Table 29-12.
The commonly used public methods of the
DataColumnMappingCollection are listed and
described in Table 29-13.
The commonly used public properties of the
DataColumnMapping class are listed and described
in Table 29-14.
The commonly used public methods of the
DataColumnMapping class are listed and described
in Table 29-15.