Intro to Microsoft.NET
- 2. Difference between Library, Framework • A Library is a reusable set of types/functions you can use from a wide variety of applications. The application code initiates communication with the library and invokes it. • A Framework consists of one or more libraries, but the difference is that Inversion of Control applies. The application registers with the framework (often by implementing one or more interfaces), and the framework calls into the application, which may call back into the framework. A framework often exists to address a particular general-purpose Domain (such as web applications, or workflows, etc.).
- 3. History of Microsoft application platforms • The Microsoft Foundation Class library (MFC) offered a C++ abstraction over GUI programming. Using MFC, developers could focus more on what their program should do and they can focus less on message loops, window procedures, window classes, and so on.
- 4. History (Cont.) • With Microsoft Visual Basic 6 and earlier, developers also had an abstraction that made it easier to build GUI applications. This abstraction technology served a purpose similar to MFC but was geared towards developers programming in Basic, and it gave different emphasis to the various parts of GUI programming
- 5. History (Cont.) • Microsoft's ASP technology offered an abstraction allowing developers to build active and dynamic Web sites by using Visual Basic Script or JScript. ASP allowed developers to focus more on the Web page content and less on the network communications
- 6. History (Cont.) • Microsoft's Active Template Library (ATL) offered an abstraction allowing developers to more easily create components that could be used by developers working in multiple programming languages.
- 7. Problems with earlier technology • Each of these abstraction technologies was designed to make it easier for developers focusing on a particular scenario such as GUI applications, Web applications, or components. If a developer wanted to build a Web site that used a component, the developer would have to learn multiple abstraction technologies: ASP and ATL.
- 8. Problems with earlier technologies (Cont.) • Furthermore, the developer would have to be proficient in multiple programming languages since ASP required either Visual Basic Script or JScript, and ATL required C++. • Frequently, the various abstraction technologies weren't originally designed to work together, so developers fought integration issues
- 9. Motivation for .NET • The .NET Framework raises the abstraction level for any and all kinds of applications. • This means that there is a single programming model and set of APIs that developers will use regardless of whether they are building a console application, graphical application, Web site, or even components for use by any of these application types.
- 10. Cross language • It is now possible to build a Web site and components that all use a single language such as Visual Basic or Microsoft's relatively new C# programming language
- 11. Simplified programming model • The CLR seeks to greatly simplify the plumbing and arcane constructs required by Win32 and COM. Specifically, the CLR now frees the developer from having to understand any of the following concepts: the registry, globally unique identifiers (GUIDs), IUnknown, AddRef, Release, HRESULTs, and so on. • The CLR doesn't just abstract these concepts away from the developer; these concepts simply don't exist in any form in the CLR. Of course, if you want to write a .NET Framework application that interoperates with existing, non-.NET code, you must still be aware of these concepts.
- 12. Easier integration • These features also mean that integration issues also go away, which greatly improves testing, deployment, administration, versioning, and re-usability and re-purposing of code
- 13. Consistent programming model • Unlike today, when commonly some operating system facilities are accessed via dynamic-link library (DLL) functions and other facilities are accessed via COM objects, all application services are offered via a common object oriented programming model.
- 14. Run once, run always • All Windows developers are familiar with "DLL hell" versioning problems. This situation occurs when components being installed for a new application overwrite components of an old application, causing the old application to exhibit strange behavior or stop functioning altogether. The architecture of the .NET Framework now isolates application components so that an application always loads the components that it was built and tested with. If the application runs after installation, the application should always run.
- 15. Simplified deployment • The .NET Framework components are not referenced by the registry. In fact, installing most .NET Framework applications requires no more than copying the files to a directory and adding a shortcut to the Start menu, desktop, or Quick Launch toolbar. Uninstalling the application is as simple as deleting the files.
- 16. Type-safe verification • Type safety ensures that allocated objects are always accessed in compatible ways. Hence, if a method input parameter is declared as accepting a 4-byte value, the CLR will detect and trap attempts to access the parameter as an 8-byte value. Similarly, if an object occupies 10 bytes in memory, the application can't coerce the object into a form that will allow more than 10 bytes to be read
- 17. Interoperability • The .NET Framework fully supports the ability for developers to access their existing COM components as well as call Win32 functions in existing DLLs.
- 18. Security • With the increasing reliance on mobile code such as Web scripts, applications downloaded over the Internet, and e-mail attachments, we need ways to control the behavior of applications in a more code-centric manner. Code access security provides a means to do this
- 19. The .NET Framework is: • Common Language Runtime – provides an abstraction layer over the operating system • Base Class Libraries – pre-built code for common low-level programming tasks • Development frameworks and technologies – reusable, customizable solutions for larger programming tasks
- 20. CLR • Using Internet Explorer to host the runtime enables you to embed managed components or Windows Forms controls in HTML documents. Hosting the runtime in this way makes managed mobile code (similar to Microsoft® ActiveX® controls) possible, but with significant improvements that only managed code can offer, such as semi-trusted execution and isolated file storage.
- 21. The class library • The other main component of the .NET Framework, is a comprehensive, object- oriented collection of reusable types that you can use to develop applications ranging from traditional command-line or graphical user interface (GUI) applications to applications based on the latest innovations provided by ASP.NET, such as Web Forms and XML Web services.
- 22. Class Library (Cont.) • The Framework Class Library provides an object-oriented API set that all application models will use. It includes type definitions that allow developers to perform file and network I/O, scheduling tasks on other threads, drawing shapes, comparing strings, and so on. Of course,all of these type definitions follow the programming model set forth by the CLR
- 23. .NET Framework in context
- 24. Common Language Runtime (CLR) • The common language runtime is the foundation of the .NET Framework. • You can think of the runtime as an agent that manages code at execution time • Provides core services such as memory management, thread management, and remoting, while also enforcing strict type safety
- 25. CLR • Code that targets the runtime is known as managed code, while code that does not target the runtime is known as unmanaged code • The .NET Framework can be hosted by unmanaged components that load the common language runtime into their processes and initiate the execution of managed code, thereby creating a software environment that can exploit both managed and unmanaged features
- 26. CLR • For example, ASP.NET hosts the runtime to provide a scalable, server-side environment for managed code. ASP.NET works directly with the runtime to enable ASP.NET applications and XML Web services • Internet Explorer is an example of an unmanaged application that hosts the runtime (in the form of a MIME type extension).
- 27. Consistent method failure paradigm • Exceptions work across module and programming language boundaries. And, unlike status codes and HRESULTs, exceptions can't be ignored. The CLR also provides built- in stack-walking facilities, making it much easier to locate any bugs and failures
- 28. Automatic memory management (garbage collection) • One of the most common bugs is neglecting to free one of these resources, ultimately causing the application to perform improperly at some unpredictable time. The CLR automatically tracks resource usage, guaranteeing that your application will never leak resources
- 29. Programming language integration • The CLR makes it possible to create a class in C++ that derives from a class implemented in Visual Basic • The CLR allows this because it defines and provides a Common Type System (CTS) that all programming languages that target the CLR must use. The Common Language Specification (CLS) describes what compiler implementers must do in order for their languages to integrate well with other languages
- 30. Wide platform reach • You can deploy your .NET Framework application on any machine that has an ECMA- compliant version of the CLR and FCL running on it