Managed Provider Factories in .NET

Version 2.0 of the Framework introduces a factory model for creating instances of data access

objects. Using this factory enables you to write code that’s generic across different database

vendors. This feature is available through ADO, but to write vendor-neutral code in .NET

requires using an interface-based late bound programming model or one of the backwards

compatibility Managed Providers, such as OLEDB or ODBC. The interface-based approach

involves programming against the interfaces common to all Managed Providers, and then

using Reflection or a custom-written factory to actually load instances of types at runtime.

The backwards compatibility layer introduces a serious performance hit to your managed

applications. This is particularly painful if the databases you’re supporting do provide Man-aged Providers coded specifically for those vendors’ platforms. You don’t ever want to, for

example, use the OLEDB Managed Provider to talk to SQL Server 2000.

So in 2.0, there’s a Provider Factory model. This factory enables you to let configuration

entries drive what database you’re to use, but get instances of types from specific Managed

Providers at runtime. So if you’re using SQL Server, you get a SqlConnection object to use from

your code. If you’re using Oracle, you get an OracleConnection.

The services of the Provider Factory are exposed through a couple of types that Microsoft

added to the System.Data.Common namespace. DbProviderFactories exposes a couple of simple

shared methods (see Table 10-6).

Table 10-6. The Shared Methods of the DbProviderFactories type

Shared Method Meaning in Life

GetFactoryClasses This method returns a DataTable with metadata about all of the

installed providers on the system.

GetFactory This method returns an instance of a DbProviderFactory type. It

accepts an argument that describes the factory—either a DataRow from

the DataTable returned by GetFactoryClasses, or an “invariant name”

of the provider, which is a column returned in the DataTable.

All of the configured Managed Providers are available through the services of the Provider

Factory. To get a list of installed providers on a system, you can use the GetFactoryClasses

method on the DbProviderFactory type (see Default.aspxin Web10).

Running Codes

protected void Page_Load(object sender, EventArgs e)

{

GridView gv = new GridView();

gv.DataSource = DbProviderFactories.GetFactoryClasses();

gv.DataBind();

form1.Controls.Add(gv);

}