With the .NET Framework, you can build many different types of applications, including the following:
ASP.NET Web applications
ASP.NET Web Services (XML Web Services)
Windows Forms custom controls
Web Forms custom controls
In this book, you will learn how to build ASP.NET Web applications and ASP.NET Web Services. You will be shown how to create Class Library (DLLs) projects to help you "componetize" your applications. This section describes each of these project types in a little more detail.
A Windows application involves a rich user interface (UI) client that runs on a Windows OS. It uses the Windows Forms engine to create the UI. Windows applications are best suited for client/server database applications, numerical control, graphical programs, or any application that needs to have a rich UI.
Windows Forms are the new form engine for Windows development. You can use Windows Forms with any CLR language. Windows Forms can be ported from one language to another easily. Windows Forms come with a rich set of standard controls built in, and you can build your own controls as well.
A Windows Service is an application that runs under Windows NT, Windows 2000 Server, or Advanced Server. These types of applications do not typically have a UI. Instead, they are used to perform some ongoing service without any interaction from a user. The OS starts a Windows Service application when the OS itself starts up. You may need to supply a security context for this service. You can create these types of applications very easily with .NET.
A Web application is an interactive set of HTML pages that run programs on a Web server. Web applications can either have a UI or not. You will be using this type of application most often as you read through this book. ASP.NET is at the heart of Web applications and is the replacement for the older Active Server Pages (ASP) technology.
ASP.NET is an enhanced version of ASP. If you have programmed in ASP before, you will find the move to ASP.NET very easy. Porting your old ASP applications to ASP.NET may prove to be somewhat of a challenge, so you might choose to rewrite as you go. ASP and ASP.NET can run side by side within the same IIS computer.
ASP.NET provides the following enhancements:
Better session statement management
Better handling of Web farms
Two to three times faster performance than ASP
Uses compiled code, as opposed to an interpreted scripting language like ASP does
Better caching techniques
Includes both Web Forms and XML Web Services for developing either a UI or non-UI application
ASP.NET Web Forms
ASP.NET Web Forms are the Internet equivalent of Windows Forms. Server-side controls have a lot of flexibility, including the capability to bind to a data source and generate a lot of HTML that otherwise would be very tedious to code. These server-side controls can generate standard HTML 3.2 or include Internet Explorer (IE) extensions for a richer UI. These server-side controls have a rich programming interface too.
XML Web Services
An XML Web Service is an application that exposes its features through XML, specifically SOAP. You use both XML and SOAP to call these services. With the .NET tools, you only need to use built-in classes to interact with and build XML Web Services you never have to see or use the XML or SOAP specifications.
You can return many types of information to users with XML Web Services, including the following:
A class library is a collection of classes that you build into one project, and you compile that project as a DLL. These libraries can then be reused in any application that you build. In Visual Basic 6.0, these Class Library projects are called COM DLLs. Although they are still DLLs in .NET, they no longer rely on COM.