Building Three-Tiered Database Applications

Building Three-Tiered Applications

topic	How do I use XML with VB?
issue	I have been hearing a lot about XML. How would I use it with Visual Basic?
version	VB6

There are several ways to use XML in a VB application:

Use XML as a way to pass data between the tiers of an application. Click here for details.
Use XML to display data from a VB application in a Web browser.
Use XML to define the metadata needed by the application.

topic	How do I pass data between the tiers of my application?
issue	I am designing a three-tiered application with my user interface component, business logic component, and my data access component. How do I get the data from the data access component to the business logic component?
version	VB6

There are several ways to do this:

Disconnected recordsets - Most popular VB6 technique
Variant arrays
User-defined types (UDTs)
Extensible Mark-up Language (XML) - Latest techniques

The attached sample code demonstrates each technique. Click here to download the sample code.

topic	How does the Data Environment designer fit into a three-tiered architecture?
issue	The Data Environment designer is very cool. But I am building three-tiered applications. Is there a use for the DE in three-tiered systems?
version	VB6

The most common use of the Data Environment (DE) is in two-tiered client/server applications in situations where you want to bind the controls directly to the DE. However, the DE can be used in middle-tier components. For example, you can add a DE to an ActiveX DLL or EXE project. Classes in that project can then use the DE for connections and commands, while still remaining stateless. The middle-tier component can then pass the recordset provided by the DE to the client tier so the client tier can use data binding.

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