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Introduction to ASP.NET
Introduction to the environment of ASP.NET
ASP.NET is more than the next version of Active Server Pages(ASP).It is a unified Web development platform that provides the services necessary for developers to build enterprise-class Web applications. While ASP.NET is largely syntax compatible with ASP, it also provides a new programming model and infrastructure for more secure, scalable, applications. You can feel free to augment your ASP applications by incrementally adding ASP.NET functionality to them.
ASP.NET is a compiled, .NET-based environment; you can author application in any .NET compatible language, including Visual Basic .NET, C#, and JScript .NET. Additionally, the entire .NET Framework is available to any ASP.NET application.Developers can easily access the benefits of these technologies, which include the managed common language runtime environment, type safety, inheritance, and so on.
ASP.NET has been designed to work seamlessly with WYSIWYG HTML editors and other programming tools, including Microsoft Visual Studio .NET. Not only does this make Web development easier, but it also provides all the benefits that these tools have to offer, including a GUI that developers can use to drop server controls onto a Web page and fully integrated debugging support.
The functions of ASP.NET
(1)If you have ASP development skills, the new ASP.NET programming model will seem very familiar to you. However, ASP.NET object has changed significantly from ASP, making it more structured and object-oriented. Unfortunately this means that ASP.NET is not fully backward compatible; all existing ASP pages will have to be modified to run under ASP.NET. In addition, major changes to Visual Basic .NET mean that ASP pages written with Visual Basic Edition typically will not directly to ASP.NET. In most cases, though, the necessary changes will involve only a few lines of code.
(2)Accessing databases from ASP.NET applications is an often-used technique for displaying data to Web site visitors. ASP.NET makes it easier than ever to access databases for this purpose. It also allows you to manage the database from your code.
(3)ASP.NET provides a simple model that enables Web developers to write logic that runs at application level. Developers can write code in Global.asax file deployed as an assembly. This logic include application-level events, but developers can easily extend this model to suit the needs of Web application.
(4)ASP.NET provides easy-to-use application and session-state facilities that are familiar to ASP developers and are readily compatible with all other .NET Framework APIs.
(5)For advanced developers who want to use APIs as powerful as the ISAPI programming interfaces that were included with previous versions of ASP, ASP.NET offers the IHttpHandler and IHttpModule interfaces. Implementing the IHttpHandler interface gives a means of interacting with the low-level request and response services of the IIS Web server and provides functionality much like ISAPI extensions, but with a simpler programming model. Implementing the IHttpModule interface allows you to include custom events that participate in every request made to your application.
(6)ASP.NET takes advantage of performance enhancements found in the .NET Framework and common language runtime. Additionally, it has been designed to offer significant performance improvements over ASP an. All ASP.NET code is compiled, rather than interpreted, which allows early binding, strong typing, and just-in-time (JIT) compilation to native code, to name only a few of its benefits. ASP.NET is also easily factorable, meaning that developers can remove modules (a session module, for instance) that are not relevant to the application.ASP.NET provides extensive caching services.ASP.NET also ships with performance counters that developers and system administrators can monitor to test new applications and gather metrics on existing applications.
(7)Writing custom debug statements to your Web page can help immensely in troubleshooting your application's code. However, they can cause embarrassment if they are not removed. The problem is that removing the debug statements from your pages when your application is ready to be ported to a production server can require significant effort. ASP.NET offers the TraceContext class, which allows you to write custom debug statements to your pages as you develop them. They appear only when you have enabled tracing for a page or entire application. Enabling tracing appends details about a request to the page, or, if you so specify, to a custom trace viewer that is stored in the root directory of your application.
(8)The .NET Framework and ASP.NET provide default authorization for Web applications. You can easily remove, add to, replace these schemes, depending upon the needs of your application.
(9)ASP.NET configuration are stored in XML-based files, which are human readable and writable. Each of your applications can have a distinct configuration file,you can extend the configuration scheme to suit your requirements. For more information, see ASP.NET Configuration.
(10)Applications are said to be running side by side when they are installed on the same computer but use different versions of the .NET Framework.
(11)IIS 6.0 uses a new process model called worker process isolation mode, which is different from the process model used in previous versions of IIS. ASP.NET uses this model by default when running on Windows Server 2003.
Building solutions with .NET technologies, you can create and connect to an infinite variety of personalized .NET experiences, with industry-standard technologies helping to protect your security and safety. Individuals can enjoy rich, tailored interactions—.NET experiences—when Web services are pulled together, allowing access to information across the Internet and from stand-alone applications, online or offline.
Most consumers will never notice that the .NET Framework is running on their Pocket PC, smartphone, or desktop computer. But they may appreciate the reliability, ease of use, and ability to connect to other systems that the .NET Framework helps bring to computers. The .NET Framework helps software developers and systems administrators more easily build and maintain systems with improvements toward performance, security, and reliability.
The Microsoft .NET Framework is an important new component of the Microsoft Windows? family of operating systems. It is the foundation of the next generation of Windows-based applications that are easier to build, deploy, and integrate with other networked systems. The .NET Framework simplifies Windows software development. It provides developers with a single approach to build both desktop applications—sometimes called smart client applications—and Web-based applications. It also enables developers to use the same tools and skills to develop software for a variety of systems ranging from handheld smartphones to large server installations.Software built on the .NET Framework can be easier to deploy and maintain than conventional software. Applications can be designed to automatically upgrade themselves to the latest version. The .NET Framework can also minimize conflicts between applications by helping incompatible software components coexist.
The .NET Framework is a new computing platform that simplifies application development in the highly distributed environment of the Internet. The .NET Framework is designed to fulfill the following objectives:
To provide a consistent object-oriented programming environment whether object code is stored and executed locally, executed locally but Internet-distributed, or executed remotely.
To provide a code-execution environment that minimizes software deployment and versioning conflicts.
To provide a code-execution environment that guarantees safe execution of code, including code created by an unknown or semi-trusted third party.
To provide a code-execution environment that eliminates the performance problems of scripted or interpreted environments. To make the developer experience consistent across widely varying types of applications, such as Windows-based applications and Web-based applications.
The .NET Framework has two main components: the common language runtime and the .NET Framework class library. 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, providing core services such as memory management, thread management, and remoting, while also enforcing strict type safety and other forms of code accuracy that ensure security and robustness. In fact, the concept of code management is a fundamental principle of the runtime. Code that targets the runtime is known as managed code, while code that does not target the runtime is known as unmanaged code. 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.
The introduction to ADO.NET
ADO.NET is designed specifically for message-based Web applications while still providing preferable functionality for other application architectures. By supporting loosely coupled access to data, ADO.NET maximizes data sharing by reducing the number of active connections to the database — reducing the possibility of multiple users contending for limited resources on the database server.
ADO.NET provides several ways to access data. If your Web application or XML Web service requires data access from multiple sources, needs to interoperate with other applications (both local and remote), or can benefit from persisting and transmitting cached results, the dataset is an excellent choice. As an alternative, ADO.NET provides data commands and data readers to communicate directly with the data source. Direct database operations using data commands and data readers include running queries and stored procedures, creating database objects, and performing direct updates and deletes using DDL commands.
ADO.NET maximizes data sharing by supporting an XML-based persistence and transmission format for the fundamental object of distributed ADO.NET applications: the dataset. A dataset is a relational data structure that can be read from, written to, or serialized using XML. ADO.NET datasets make it easy to build applications that require loosely coupled data interchange between application tiers and multiple Web sites.
Because datasets are remoted as XML, any two components can share data and use XML schemas to define the relational structure of the dataset. And, because the dataset's serialization format is XML, DataSet objects can easily pass through firewalls without restrictions. In addition to loading data from XML, datasets can be populated with, and hold changes to, data from SQL Server as well as data sources exposed via OLE DB.
英文翻譯
1 ASP.NET環境簡介
ASP.NET 不僅僅是下壹版本的 Active Server Page (ASP)；它是統壹的 Web 開發平臺，用來提供開發人員生成企業級 Web 應用程序所需的服務。ASP.NET 的語法在很大程度上與 ASP 兼容，同時它還提供壹種新的編程模型和結構，用於生成更安全、可伸縮和穩定的應用程序。可以通過在現有 ASP 應用程序中逐
漸添加 ASP.NET 功能，隨時增強該 ASP 應用程序的功能。
ASP.NET 是壹個已編譯的、基於 .NET 的環境，可以用任何與 .NET 兼容的語言（包括 Visual Basic .NET、C# 和 JScript .NET.）創作應用程序。另外，任何 ASP.NET 應用程序都可以使用整個 .NET Framework。開發人員可以方便地獲得這些技術的優點，其中包括托管的公***語言運行庫環境、類型安全、繼承等等。
ASP.NET 可以無縫地與 WYSIWYG HTML 編輯器和其他編程工具（包括 Microsoft Visual Studio .NET）壹起工作。這不僅使得 Web 開發更加方便，而且還能提供這些工具必須提供的所有優點，包括開發人員可以用來將服務器控件拖放到 Web 頁的 GUI 和完全集成的調試支持。
2 ASP.NET 的功能
(1)如果具有 ASP 開發技能，則對新的 ASP.NET 編程模型將會是非常熟悉的。不過，與 ASP 相比，ASP.NET 對象模型變化顯著，它更為結構化並且面向對象。但這也意味著 ASP.NET 不是完全向後兼容的；幾乎所有現有的 ASP 頁都必須經過壹定程度的修改後才可以在 ASP.NET 下運行。此外，對 Visual Basic .NET 的壹些主要更改也意味著，用 Visual Basic Scripting 版本編寫的現有 ASP 頁通常將不會直接移植到 ASP.NET 中。不過，在大多數情況下，只需對少數幾行代碼進行必要的修改。
(2)從 ASP.NET 應用程序訪問數據庫是向 Web 站點訪問者顯示數據的常用技術。ASP.NET 使得為此目的而對數據庫的訪問比以往更加方便。它還使您能夠從您的代碼管理數據庫。
(3)ASP.NET 提供壹種簡單的模型，該模型使 Web 開發人員能夠編寫在應用程序級運行的邏輯。開發人員可以在 Global.asax 文本文件中或在作為程序集部署的已編譯類中編寫這種代碼。這種邏輯可以包括應用程序級事件，但開發人員可以輕松地擴展這種模型，以適應他們的 Web 應用程序的需要。
(4)ASP.NET 提供易用的應用程序和會話狀態功能，它們對於 ASP 開發人員來說是熟悉的，且容易與所有其他 .NET Framework API 兼容。
(5)對於需要使用像 ISAPI 編程接口（隨附於以前的 ASP 版本中）那樣功能強大的 API 的高級開發人員，ASP.NET 提供了IHttpHandler 和 IHttpModule 接口。實現IHttpHandler接口，給您提供了壹種與 IIS Web 服務器的低級別請求和響應服務交互的手段，並提供與 ISAPI 擴展非常類似的功能，但編程模型卻較為簡單。實現 IHttpModule接口使您可以包含參與對應用程序發出的每個請求的自定義事件。
(6)ASP.NET 利用 .NET Framework和公***語言運行庫中的性能增強功能。另外，它還可以提供相對於ASP和其他Web開發平臺來說顯著的性能改進。所有 ASP.NET 代碼都是編譯的，而不是解釋的，這就允許對本機代碼采用早期綁定，強類型處理，以及實時(JIT)編譯，這裏只列舉幾個優點而已。ASP.NET還可方便地分解，即開發人員可以移除那些與他們開發的應用程序不相關的模塊（例如，會話模塊）。ASP.NET還提供豐富的緩存服務（包括內置服務和緩存 API 兩種）。ASP.NET還提供性能計數器，開發人員和系統管理員可以監視這些性能計數器，以測試新的應用程序和搜集有關現有應用程序的度量標準。
(7)在Web頁中編寫自定義調試語句，對排除應用程序代碼中的錯誤非常有幫助。但是，如果不移除它們，則會帶來麻煩。問題是，在應用程序準備好移植到生產服務器時從頁面中移除調試語句，會需要很大的工作量。ASP.NET 提供 TraceContext類，在開發頁面時該類用於在頁面上編寫自定義調試語句。只有當您已經對頁面或整個應用程序啟用跟蹤時它們才出現。啟用跟蹤還將有關請求的細節追加到頁面，或者，追加到存儲在應用程序根目錄中的自定義跟蹤查看器（如果這樣指定的話）。
(8).NET Framework和ASP.NET為Web應用程序提供默認授權和驗證方案。可以方便地移除、添加或者替換這些方案，這取決於應用程序的需要。
(9)ASP.NET 配置設置存儲在基於 XML 的文件中，這些文件都是人可讀和可寫的。每壹個應用程序都可以有不同的配置文件，可以擴展配置方案，以適應您的要求。
(10)當應用程序安裝在同壹臺計算機上，但使用不同的 .NET Framework 版本時，就說應用程序是並行運行的。
(11)IIS 6.0 使用壹個稱為輔助進程隔離模式的新進程模型，它不同於 IIS 早期版本中使用的進程模型。當在 Windows Server 2003 上運行時，默認情況下 ASP.NET 使用該進程模型。
使用.NET技術構建解決方案，妳可以創建和連接壹個無限變化的個性化的.NET體驗.用工業標準的技術有助於保護妳的隱私和安全.可以充分享受.NET帶來的無盡的個性和精心特制的交互.壹旦.NET XML Web 服務被集成時，就可以用壹個獨立的應用程序通過互聯網在線或離線地獲取信息.
大多數消費者可能永遠不會註意到.NET框架運行在他們的Pocket PC(掌上電腦PDA)，智能電話，或是桌面機之上.盡管如此，消費者卻自始至終地可以享受到.NET框架在幕後帶來的可靠性，易用性，互聯性。開發者，系統管理員可在.NET框架下更容易地創建和維護系統，以獲得更好的性能，更高的安全，更強的可靠。
.NET框架是微軟Windows系列操作系統的壹個新的重要的組件.它是下壹代Windows應用程序的根基，非常容易開發和布署，整合至其他的網絡系統。.NET框架簡化了Windows平臺的軟件開發,為開發者提供了創建桌面應用程序(有時稱為智能客戶應用程序)和基於Web的應用程序的壹條捷徑,允許開發者利用相同的工具，經驗開發從手持智能電話到大型服務器的各種不同系統的應用軟件.基於.NET框架的應用程序比傳統的應用程序更易於布署，維護.應用程序可被設計成可自動更新到其最新版本。.NET框架也能最小化***存的不兼容的組件間的沖突.
.NET Framework 是壹種新的計算平臺，它簡化了在高度分布式 Internet 環境中的應用程序開發。.NET Framework 旨在實現下列目標：
提供壹個壹致的面向對象的編程環境，而無論對象代碼是在本地存儲和執行，還是在本地執行但在 Internet 上分布，或者是在遠程執行的。
提供壹個將軟件部署和版本控制沖突最小化的代碼執行環境。
提供壹個保證代碼（包括由未知的或不完全受信任的第三方創建的代碼）安全執行的代碼執行環境。
提供壹個可消除腳本環境或解釋環境的性能問題的代碼執行環境。使開發人員的經驗在面對類型大不相同的應用程序（如基於 Windows 的應用程序和基於 Web 的應用程序）時保持壹致。按照工業標準生成所有通信，以確保基於 .NET Framework 的代碼可與任何其他代碼集成。
.NET Framework 具有兩個主要組件：公***語言運行庫和 .NET Framework 類庫。公***語言運行庫是 .NET Framework 的基礎。您可以將運行庫看作壹個在執行時管理代碼的代理，它提供核心服務(如內存管理、線程管理和遠程處理)，而且還強制實施嚴格的類型安全以及可確保安全性和可靠性的其他形式的代碼準確性。事實上，代碼管理的概念是運行庫的基本原則。以運行庫為目標的代碼稱為托管代碼，而不以運行庫為目標的代碼稱為非托管代碼。.NET Framework 的另壹個主要組件是類庫，它是壹個綜合性的面向對象的可重用類型集合，您可以使用它開發多種應用程序，這些應用程序包括傳統的命令行或圖形用戶界面 (GUI) 應用程序，也包括基於 ASP.NET 所提供的最新創新的應用程序(如 Web 窗體和 XML Web services)。
3 ADO.NET的介紹
ADO.NET 是專為基於消息的 Web 應用程序而設計的，同時還能為其他應用程序結構提供較好的功能。通過支持對數據的松耦合訪問，ADO.NET 減少了與數據庫的活動連接數目（即減少了多個用戶爭用數據庫服務器上的有限資源的可能性），從而實現了最大程度的數據***享。
ADO.NET 提供幾種數據訪問方法。在有些情況下，Web 應用程序或 XML Web services 需要訪問多個源中的數據，或者需要與其他應用程序（包括本地和遠程應用程序）進行互操作，或者可受益於保持和傳輸緩存結果，這時使用數據集將是壹個明智的選擇。作為壹種替換方法，ADO.NET 提供數據命令和數據讀取器以便與數據源直接通信。使用數據命令和數據讀取器直接進行的數據庫操作包括：運行查詢和存儲過程、創建數據庫對象、使用 DDL 命令直接更新和刪除。
ADO.NET 還通過對分布式 ADO.NET 應用程序的基本對象“數據集”(Dataset)支持基於 XML 的持久性和傳輸格式，來實現最大程度的數據***享。數據集是壹種關系數據結構，可使用 XML 進行讀取、寫入或序列化。ADO.NET 數據集使得生成要求應用程序層與多個 Web 站點之間進行松耦合數據交換的應用程序變得很方便。
因為數據集被遠程處理為 XML 形式，所以任何兩個組件都可***享數據並使用 XML 架構來定義數據集的關系結構。而且，因為數據集的序列化格式是 XML，所以 DataSet 對象可輕松穿過防火墻，而不受任何限制。除了從 XML 加載數據以外，數據集還可用 SQL Server 中的數據以及通過 OLE DB 公開的數據源中的數據來填充，並可保存對這些數據的更改。