Content Summary : In this chapter we change our focus from building Windows Applications to building Web Applications. That is, instead of building applications that run entirely on the user’s computer, we look at applications where various parts of the application run on the user’s computer (the client) as well as on other computers (servers). Visual Basic .NET provides a powerful set of tools that support the development and testing of Web Applications using Microsoft’s ASP.NET technology. We begin by explaining and contrasting a number of different Web architecture options. We break an application into its three primary functions – presentation (GUI), processing business logic, and data management. We look at how these three functions can be located on the client and servers and evaluate the advantages and disadvantages of the various options. We then turn our attention to Visual Basic .NET and how it supports the various Web architectures. We look at creating a basic Web Application project and how to run it using the Microsoft IIS Web Server. We look at validating data (both on the client and on the server) using various Visual Basic .NET Validation controls. We next focus on processing databases in the context of Web Applications where the data are typically located on a server distinct from the client. We present the version of the DataGrid control designed to be processed on the server and look first at a simple example that displays data from a database. Next we see how the DataGrid control can support field editing with changes coming from the user at the client and the database changes being processed on the server. Lastly we look at an example that shows how XML and XSLT can be used to transform XML into different views on the server and then rendered for viewing on the client.