Retrieving Database Schema Information
Obtaining schema information from a database is accomplished with the process of schema discovery. Schema discovery allows applications to request that managed providers find and return information about the database schema, also known as metadata, of a given database. Different database schema elements such as tables, columns, and stored-procedures are exposed through schema collections. Each schema collection contains a variety of schema information specific to the provider being used.
Each of the .NET Framework managed providers implement the GetSchema method in the Connection class, and the schema information that is returned from the GetSchema method comes in the form of a DataTable. The GetSchema method is an overloaded method that provides optional parameters for specifying the schema collection to return, and restricting the amount of information returned.
The .NET Framework Data Providers for OLE DB, ODBC, Oracle, and SqlClient provide a GetSchemaTable method that returns a DataTable describing the column metadata of the DataReader.
The .NET Framework Data Provider for OLE DB also exposes schema information by using the GetOleDbSchemaTable method of the OleDbConnection object. As arguments, GetOleDbSchemaTable takes an OleDbSchemaGuid that identifies the schema information to return, and an array of restrictions on those returned columns. GetOleDbSchemaTable returns a DataTable populated with the requested schema information.