SqlCeDataReader.GetSchemaTable Method

Article
10/22/2007

Returns a DataTable that describes the column metadata of the SqlCeDataReader.

Namespace: System.Data.SqlServerCe
Assembly: System.Data.SqlServerCe (in system.data.sqlserverce.dll)

Syntax

'Declaration
Public Overrides Function GetSchemaTable As DataTable
'Usage
Dim instance As SqlCeDataReader
Dim returnValue As DataTable

returnValue = instance.GetSchemaTable

public override DataTable GetSchemaTable ()

public:
virtual DataTable^ GetSchemaTable () override

public DataTable GetSchemaTable ()

public override function GetSchemaTable () : DataTable

Return Value

A DataTable that describes the column metadata.

Exceptions

Exception type	Condition
InvalidOperationException	The operation is not valid. The SqlCeDataReader may be positioned after the last row in the result set.

Remarks

If SqlCeDataReader is reading columns from more than one base table, SqlCeDataReader will not populate the schema table with IsKey values. This behavior is similar to what happens when you have a SELECT query:

SELECT FirstName, LastName, 1+2 FROM Employees

The query is reading columns from two different tables, the Employees table in the Northwind database and the temporary table created for 1+2.

The GetSchemaTable method maps to the OLE DB IColumnsRowset::GetColumnsRowset method, and returns metadata about each column in the following order:

Schema Table Column	Description
ColumnName	The name of the column. This name might not be unique. If the name cannot be determined, a a null reference (Nothing in Visual Basic) value is returned. This name always reflects the most recent renaming of the column in the current view or command text.
ColumnOrdinal	The ordinal of the column. The ordinal number starts with zero. SQL Server Mobile does not support bookmarks.
ColumnSize	The maximum possible length of a value in the column. For columns that use a fixed-length data type, the maximum length is the size of the data type.
NumericPrecision	If ProviderType is a numeric data type, the maximum precision of the column. The precision depends on the definition of the column. If ProviderType is not a numeric data type, a a null reference (Nothing in Visual Basic) value.
NumericScale	If ProviderType is DBTYPE_DECIMAL or DBTYPE_NUMERIC, the number of digits to the right of the decimal point. Otherwise, this is a a null reference (Nothing in Visual Basic) value.
IsUnique	If true, no two rows in the base table—which is the table returned in BaseTableName—can have the same value in this column. IsUnique is guaranteed to be true if the column constitutes a key by itself or if there is a constraint of type UNIQUE that applies only to this column. If false, the column can contain duplicate values in the base table. The default of this column is false.
IsKey	If true, the column is one of a set of columns in the rowset that, taken together, uniquely identify the row. The set of columns with IsKey set to true must uniquely identify a row in the rowset. There is no requirement that this set of columns is a minimal set of columns. This set of columns may be generated from a base table primary key, a unique constraint, or a unique index. If false, the column is not required to uniquely identify the row.
BaseColumnName	The name of the column in the data store. The name is a a null reference (Nothing in Visual Basic) value if the base column name cannot be determined or if the rowset column is derived, but not identical to, a column in the data store. The default of this column is a a null reference (Nothing in Visual Basic) value.
BaseTableName	The name of the table in the data store that contains the column. The name is a a null reference (Nothing in Visual Basic) value if the base table name cannot be determined. The default of this column is a a null reference (Nothing in Visual Basic) value.
DataType	Maps to the .NET Framework type of the column.
AllowDBNull	Set if the consumer can set the column to a a null reference (Nothing in Visual Basic) value or if the provider cannot determine whether or not the consumer can set the column to a a null reference (Nothing in Visual Basic) value. Otherwise, not set. A column may contain a null reference (Nothing in Visual Basic) values, even if it cannot be set to a a null reference (Nothing in Visual Basic) value.
ProviderType	The indicator of the column's data type. This column cannot contain a null value.
IsAutoIncrement	If true, the column assigns values to new rows in fixed increments. If false, the column does not assign values to new rows in fixed increments. The default of this column is false.
IsRowVersion	Set if the column contains a persistent row identifier that cannot be written to, and has no meaningful value except to identify the row.
IsLong	Set if the column contains a Binary Long Object (BLOB) that contains very long data.
IsReadOnly	If true, the column can be modified. If false, the column cannot be modified.

.NET Framework Security

Full trust for the immediate caller. This member cannot be used by partially trusted code. For more information, see .

Platforms

Windows CE, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows XP Professional x64 Edition, Windows XP SP2

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

Version Information

.NET Compact Framework

Supported in: 2.0, 1.0

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