Introduction To Dotnet

Editor's Notes

• #3: .NET is a broad initiative that can be viewed from several perspectives.
• #4: .NET will enable the next generation of applications.
• #5: Microsoft is providing a suite of products and services to facilitate building this next generation. This course focuses on the .NET Framework and Visual Studio.NET.
• #7: Each blue box represents a separate computer (or cluster of computers).
• #8: The definition of a Web service is “a programmable application component accessible via standard Web protocols.” In other words, it is a component that can be called remotely from a client application, over the Internet. Web Services will allow people, companies, customers, suppliers, doctors, patients, etc. to interact using different computers, different operating systems, and different applications. For example, you could use the same Web Service to store your personal and work calendar information. You could access this information from different applications and view and change it in different ways.
• #9: The first generation of Web applications was largely about delivering non-interactive content, i.e. publishing non-interactive HTML pages. For example, many applications simply operated in client/server mode and rendered HTML pages to send across the internet to browsers. The second generation of Web applications was about creating applications usable over the Web. E-commerce is an example; you can go to http://www.barnesandnoble.com/ select books, order them and pay for them. This second generation also includes a more scalable back-end (e.g. WinDNA architecture) and a richer UI (e.g. DHTML and ActiveX). However, useful though they may be, the second generation largely resulted in application islands on the Web. Yes, there are hyperlinks between sites, but for the most part, the actual applications at different sites do not interact. The third generation of Web application is about using Web protocols and XML throughout to allow better integration between services on the Web. Protocols such as XML and SOAP allow you to create Web Services, enabling people and companies to easily create integrated applications.
• #10: The .NET Framework provides a set of technologies that makes creating, deploying, using and maintaining applications (including Web applications and Web Services) much easier and more robust.
• #11: The .NET framework exposes numerous classes to the developer. These classes allow the development of rich client applications and Web-based applications alike. The classes are shown here, divided into four areas. ASP.NET provides the core Web infrastructure, such as Web Forms for UI-based development and Web Services for programmatic interface development. User interface development on the Windows platform can be done using Windows Forms. ADO.NET and XML provide the functionality for data access. The core base classes provide infrastructure services such as security and transaction management. You can create code in any of a large number of languages. This code will integrate in a deep, seamless manner via a standard called the Common Language Specification. Visual Studio.NET provides tools that increases your productivity when creating applications.
• #12: This is but a brief illustration of the breadth of classes provided by the .NET Framework. We will explore many of these classes during this course. All of these classes are available to ALL languages.
• #13: The Common Language Runtime provides the underlying infrastructure for the .NET Framework. It provides very little application-visible functionality itself (security being a notable exception), but provides services to make development, deployment and execution much better in almost every way.
• #14: As a developer you can write code in the language of your choice. Your code is compiled into an Assembly, which is represented as a DLL or EXE.
• #15: IL is always compiled, never interpreted.
• #17: When an assembly starts running, the JIT (Just In Time) compiler in the Common Language Runtime converts the IL in the assembly to efficient machine code. It is this code that is actually executed.
• #18: The CLR provides many sophisticated services.
• #19: The CTS supports many types of data. It allows each language to implement its own unique features. The CLS allows different languages to interoperate in a deep manner. For example, you can create a class in C# that derives from a class written in Eiffel, and is called from a Perl program.
• #20: When we execute an application, how are the required assemblies located? Quite simply; the class loader (part of the CLR) will search the current directory for any assemblies. Assemblies should be kept within the same directory as the application that requires them. This allows different versions of the software to be installed on the machine without interfering with each other. However, if required, it is possible to share an assembly using the global assembly cache.
• #21: Before code in an assembly is run, the CLR looks at the identity of both the user and the code. You can specify policies that determine which code can be executed, and the priviledges that code will have when it runs.
• #22: Windows Forms is a framework for building rich Windows client applications, and can be written in any language that supports .NET. Windows Forms provide the developer with many features, such as: The simplicity that Visual Basic 6 programmers are used to. Easy deployment. Windows Forms (as .NET applications) automatically takes advantage of the versioning and deployment features of the .NET Framework. Windows Forms offers an architecture for controls and control containers based on concrete implementation of the control and container classes. This significantly reduces control-container interoperability issues. Security. Windows Forms takes full advantage of the security features of .NET. This means that Windows Forms can be used to implement everything from an untrusted control running in the browser to a fully trusted application installed on a user's hard drive. Web Services Support. Windows Forms offer full support for quickly and easily connecting to Web Services. Rich Graphics. Controls. Windows Forms offer a rich set of controls that encompass all of the controls offered by Windows and new features such as new "flat look" styles for Buttons, Radio Buttons and Checkboxes. Data Awareness. Windows Forms offer full support for the ADO.NET data model. ActiveX Controls. Windows Forms offer full support for ActiveX controls. You can easily host ActiveX controls in a Windows Forms application. You can also host a Windows Form control as an ActiveX control. Licensing. Windows Forms take advantage of the .NET Framework enhanced licensing model. Printing. Windows Forms offer a printing framework that enables applications to provide comprehensive reports. Accessibility. Windows Form controls implement the interfaces defined by Microsoft Active Accessibility (MSAA), making it straightforward to build applications that support accessibility aids such as screen readers.
• #23: The first incarnation of ASP proved very successful. As part of the .NET Framework, Microsoft supports ASP.NET. ASP.NET is a logical evolution of ASP that addresses many of the issues previously associated with ASP. ASP.NET is now compiled and not interpreted. This of course can go some way towards improving efficiency and also means that code can now support strongly typed variables other than VARIANTS. This makes ASP.NET much more flexible and easier to code. A great deal of work has also been done to make sure that ASP.NET development has become cleaner and more productive.
• #26: ADO.NET evolves from ADO, and is designed to deal with the issues of state, scalability and XML compatibility. Although existing ADO developers will find all of the old ADO classes inside the ADO.NET data model, they will also find that a few new classes have been introduced, including the DataSets, DataReaders and DataSetCommands classes.
• #27: C# is a new language designed to take advantage of most of the features of the .NET Framework. C# was designed from the ground up to support component concepts like events, methods and properties. In C#, everything is an object, which allows the creation of very clean designs. C# was designed to make it easy to create robust and maintainable software. C# should allow you to preserve your existing investment by integrating easily with your existing code.
• #28: VB.NET is a modernized version of Visual Basic. It is integrated with the .NET Framework, but still provides language constructs, features and syntax that is familiar to Visual Basic developers.