INTRODUCING VISUAL BASIC AND THE .NET FRAMEWORK in Font

Maker DataMatrix in Font INTRODUCING VISUAL BASIC AND THE .NET FRAMEWORK

Now that you have seen some of the major goals of the .NET Framework, let s take a look at the components it comprises.

The fundamental component of the .NET Framework is the CLR. The CLR manages the code being executed and provides for a layer of extraction between the code and the operating system. Built into the CLR are mechanisms for the following: Loading code into memory and preparing it for execution Converting the code from the intermediate language to native code Managing code execution Managing code and user-level security Automating deallocation and release of memory Debugging and tracing code execution Providing structured exception handling

Built on top of the CLR is the .NET Framework base class library. Included in this class library are reference types and value types that encapsulate access to the system functionality. Types are data structures. A reference type is a complex type for example, classes and interfaces. A value type is simple type for example, integer or Boolean. Programmers use these base classes and interfaces as the foundation on which they build applications, components, and controls. The base class library includes types that encapsulate data structures, perform basic input/output operations, invoke security management, manage network communication, and perform many other functions.

Built on top of the base classes are classes that support data management. This set of classes is commonly referred to as ADO.NET. Using the ADO.NET object model, programmers can access and manage data stored in a variety of data storage structures through managed providers. Microsoft has written and tuned the ADO.NET classes and object model to work efficiently in a loosely coupled, disconnected, multitiered environment. Under the hood, ADO.NET works with data in an XML-structured format. Using this type of structure instead of a binary format makes it much easier to pass data using the Hypertext Transfer Protocol (HTTP) and to share data between disparate systems. Another advantage of ADO.NET is that it not only exposes the data from the database, but also exposes the metadata associated with the data. Data is exposed as a sort of mini-relational database. This means that you can get the data and work with it while disconnected from the data source and later synchronize the data with the data source. Microsoft has provided support for several data providers. Data stored in Microsoft SQL Server 7.0 and later can be accessed through the native SQL data provider. OLEDB and Open Database Connectivity (ODBC) managed providers are two generic providers for systems

currently exposed through the OLEDB or ODBC standard APIs. Because these managed data providers do not interface directly with the database engine but rather talk to the unmanaged provider, which then talks to the database engine, using non-native data providers is less efficient and robust than using a native provider. Because of the extensibility of the .NET Framework and Microsoft s commitment to open-based standards, many data storage vendors now supply native data providers for their systems. ADO.NET is heavily dependent on XML to store, manipulate, and pass data and metadata. Rich support is provided by ADO.NET to manipulate, search, and transform XML data. In fact, programmers using ADO.NET can work with any data storage device on any platform that can expose its data in a standard XML format. You can also read in an XML data structure, expose it as a relational data structure for clients to work with and manipulate, and then convert it back to an XML format for data storage or transport.

The .NET Framework exposes a base set of classes that can be used on a web server to create user interfaces and services exposed to web-enabled clients. These classes are collectively referred to as ASP .NET. Using ASP .NET, you can develop one user interface that can dynamically respond to the type of client device making the request. At runtime, the .NET Framework takes care of discovering the type of client making the request (browser type and version) and exposing an appropriate interface. The GUIs for web applications running on a Windows client have become more robust because the .NET Framework exposes much of the API functionality that previously had been exposed only to traditional Windows Forms-based C++ and VB applications. Another improvement in web application development using the .NET Framework is that server-side code can be written in any .NET-compliant language. Prior to .NET, server-side code had to be written in a scripting language such as VBScript or JScript. Incorporated into ASP.NET are base class and interface support for creating web-based services. Microsoft s vision is that web services will provide functionality similar to the components developed using previous versions of Visual C++ (VC++) and VB. Because these components were based on binary standards, it was not easy to communicate with the components through firewalls and across the Internet. The proprietary nature of the components also limited the types of clients that could effectively use and interact with the components. Microsoft has addressed these limitations by exposing web services through Internet standards such as XML and SOAP The current version of web services components can easily interact and expose their . services to any client that is XML-enabled and can communicate via HTTP .