【正文】 ion on screen or sing a song, but cannot access their personal data, file system, or work. The security features of the runtime thus enable legitimate Interdeployed software to be exceptionally feature rich. The runtime also enforces code robustness by implementing a strict typeandcodeverification infrastructure called the mon type system (CTS). The CTS ensures that all managed code is selfdescribing. The various Microsoft and thirdparty language pilers generate managed code that conforms to the CTS. This means that managed code can consume other managed types and instances, while strictly enforcing type fidelity and type safety. In addition, the managed environment of the runtime eliminates many mon software issues. For example, the runtime automatically handles object layout and manages references to objects, releasing them when they are no longer being used. This automatic memory management resolves the two most mon application errors, memory leaks and invalid memory references. The runtime also accelerates developer productivity. For example, programmers can write applications in their development language of choice, yet take full advantage of the runtime, the class library, and ponents written in other languages by other developers. Any piler vendor who chooses to target the runtime can do so. Language pilers that target the .NET Framework make the features of the .NET Framework available to existing code written in that language, greatly easing the migration process for existing applications. While the runtime is designed for the software of the future, it also supports software of today and yesterday. Interoperability between managed and unmanaged code enables developers to continue to use necessary COM ponents and DLLs. The runtime is designed to enhance performance. Although the mon language runtime provides many standard runtime services, managed code is never interpreted. A feature called justintime (JIT) piling enables all managed code to run in the native machine language of the system on which it is executing. Meanwhile, the memory manager removes the possibilities of fragmented memory and increases memory localityofreference to further increase performance. Finally, the runtime can be hosted by highperformance, serverside applications, such as Microsoft174。 Overview of the .NET Framework The .NET Framework is an integral Windows ponent that supports building and running the next generation of applications and XML Web services. The .NET Framework is designed to fulfill the following objectives: ? To provide a consistent objectoriented programming environment whether object code is stored and executed locally, executed locally but Interdistributed, or executed remotely. ? To provide a codeexecution environment that minimizes software deployment and versioning conflicts. ? To provide a codeexecution environment that promotes safe execution of code, including code created by an unknown or semitrusted third party. ? To provide a codeexecution 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 Windowsbased applications and Webbased applications. ? To build all munication on industry standards to ensure that code based on the .NET Framework can integrate with any other code. The .NET Framework has two main ponents: the mon language runtime and the .NET Framework class library. The mon 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 promote 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 ponent of the .NET Framework, is a prehensive, objectoriented collection of reusable types that you can use to develop applications ranging from traditional mandline or graphical user interface (GUI) applications to applications based on the latest innovations provided by , such as Web Forms and XML Web services. The .NET Framework can be hosted by unmanaged ponents that load the mon 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. The .NET Framework not only provides several runtime hosts, but also supports the development of thirdparty runtime hosts. For example, hosts the runtime to provide a scalable, serverside environment for managed code. works directly with the runtime to enable applications and XML Web services, both of which are discussed later in this topic. Inter Explorer is an example of an unmanaged application that hosts the runtime (in the form of a MIME type extension). Using Inter Explorer to host the runtime enables you to embed managed ponents or Windows Forms controls in HTML documents. Hosting the runtime in this way makes managed mobile code (similar to Microsoft174。 [C] protected virtual object SaveViewState()。 基類 Control 為此目的提供兩個方法： SaveViewState 和 LoadViewState。 使用 ViewState 自定義狀態(tài)還原 為了提高效率，或者為了保存默認(rèn)情況下不能在 ViewState 中存儲的自定義類型，控件可以自定義在 ViewState 中存儲屬性數(shù)據(jù)的方式。如果有若干依賴通用數(shù)據(jù) 的屬性，則可以通過只將關(guān)鍵元素存留到 ViewState 來優(yōu)化性能。 ViewState 和性能 控件開發(fā)人員應(yīng)該知道， ViewState 中的任何數(shù)據(jù)自動生成到客戶端的往返過程。但是，與具有 TypeConverter 的那些類型相比，只可序列化的類型不但更慢而且生成大得多的 ViewState。 } set { ViewState[Text] = value。） 以下代碼段說明在 ViewState 中保存的