2002-05-02 Daniel Morgan <danmorg@sc.rr.com>

2002-05-02  Daniel Morgan <danmorg@sc.rr.com>

	* System.Data.SqlClient/PostgresLibrary.cs: included new
	internal class that will be a helper class in using
	PostgreSQL.  PostgresLibrary is used for the
	pinvoke methods to the PostgreSQL Client
	native C library libpq while the class PostgresHelper
	is used for	wrapper or helper methods.  It currently only
	has one static method OidTypeToSystem in converting
	PostgreSQL types to .NET System.<type>s, such as,
	a PostgreSQL int8 becomes a .NET System.Int64.
	Only a few types have been added, such as, int2,
	int4, int8, varchar, text, bool, and char.  Other types
	will come later.

	* System.Data.SqlClient/SqlCommand.cs: implemented
	method ExecuteScalar which allows us to do aggregate
	functions, such as, count, avg, min, max, and sum.  We
	also are able to retrieve the result, convert it to the .NET type
	as an object.  The user of the returned object must explicitly cast.

	* Test/ReadPostgresData.cs: updated sample
	to help us learn to retrieve data in System.Data.SqlClient
	classes

svn path=/trunk/mcs/; revision=4217