【正文】 nd C++. A great deal of the functionality of these programming languages overlaps. For example, for each language, you would have to include methods for accessing the file system, working with databases, and manipulating strings. Furthermore, these languages contain similar programming constructs. Every language, for example, can represent loops and conditionals. Even though the syntax of a conditional written in Visual Basic differs from the syntax of a conditional written in C++, the programming function is the same. Finally, most programming languages have similar variable data types. In most languages, you have some means of representing strings and integers, for example. The maximum and minimum size of an integer might depend on the language, but the basic data type is the same. Maintaining all this functionality for multiple languages requires a lot of work. Why keep reinventing the wheel? Wouldn39。ll find it easy to make the transition between the two languages. NOTE Microsoft includes an interesting tool named the IL Disassembler (ILDASM) with the .NET framework. You can use this tool to view the disassembled code for any of the classes in the Temporary Files directory. It lists all the methods and properties of the class and enables you to view the intermediatelevel code. This tool also works with all the controls discussed in this chapter. For example, you can use the IL Disassembler to view the intermediatelevel code for the TextBox control (located in a file named ). Introducing Controls controls provide the dynamic and interactive portions of the user interface for your Web application. The controls render the content that the users of your Web site actually see and interact with. For example, you can use controls to create HTML form elements, interactive calendars, and rotating banner advertisements. controls coexist peacefully with HTML content. Typically, you create the static areas of your Web pages with normal HTML content and create the dynamic or interactive portions with controls. The best way to understand how controls work in an HTML page is to look at a simple Web Forms Page. Adding Application Logic to an Page The second building block of an page is the application logic, which is the actual programming code in the page. You add application logic to a page to handle both control and page events. If a user clicks a Button control within an HTML form, for example, the Button control raises an event (the Click event). Typically, you want to add code to the page that does something in response to this event. For example, when someone clicks the Button control, you might want to save the form data to a file or database. Controls are not the only things that can raise events. An page itself raises several events every time it is requested. For example, whenever you request a page, the page39。s preferences. Finally, imagine that you want to break the tax form into multiple pages so that a person views only one part of the tax form at a time. In the following sections, you learn about the properties that you can use to hide and display controls in a form. You learn how to use the Visible and Enabled properties with individual controls and groups of controls to hide and display page content. Using the Visible and Enabled Properties Every control, including both HTML and Web controls, has a Visible property that determines whether the control is rendered. When a control39。 .NET類庫 假想你是微軟。 每種語言 ,舉例來說，都能夠使用循環(huán)語句和條件語句。舉例來說， 整型數(shù)據(jù)最大值和最小值可能依賴語言的種類，但是基本的數(shù)據(jù)類型是相同的。 它含有大量的滿足編程需要的類。 最重要地 , 寫這一本書的目的 , .NET類庫包含構(gòu)建的 頁面的類。 (超過 3,400) 幸運(yùn)地，類不是簡單的堆在一 起。 舉例來說，涉及到與文件系統(tǒng)協(xié)同工作的類就集合 在 命名空間中。 你通過完整的類的命名空間能唯一識別任何的類在 .NET framework中的位置 。 標(biāo)準(zhǔn)的 命名空間 在默認(rèn)情況下，在你的 ，類被包含在一個選定的命名空間中這些默認(rèn)的命名空間使你在 。 命名空間 包括 files類。 命 名空間 包含頁面緩沖內(nèi)容和自定義緩沖操作的類。 包含 HTML 控件的類。雖然你在這一本書中一直用 Visual Basic, 但是，你也需要了解用其它的支持公共語言庫的語言創(chuàng)建 。 這些其他的語言的一些例子包括 Python、 SmallTalk 、 Eiffel和 COBOL。對于一個 Temporary Files目錄下。 這些迷惑的方面體現(xiàn)在整 個過程都在后臺運(yùn)行，你必須要做的是用資源代碼為你的 。 Visual Basic 是一個 VBScript 的超集 ,意味著 Visual Basic 相對于 VBScript有更多的功能。 假如你過去只用 VBScript而不用 Visual Basic，也不用擔(dān)心。 它列出了類的所有方法和屬性使你能夠?yàn)g覽中間代碼。這些控件能夠使你的網(wǎng)站的使用者看見和交互。 了解 控件是怎么工作的？最好的方法是看一個簡單的 Web應(yīng)用窗體頁面。 舉例來說，當(dāng)某人單擊 Button按鈕控件的時(shí)候，你可以保存窗體數(shù)據(jù)到一個文件或者數(shù)據(jù)庫。 每當(dāng)初始化事件發(fā)生的時(shí)候，你能夠添加代碼到頁面中來執(zhí)行。首先，你學(xué)會怎么把一個 HTML窗體鏈接到另一個頁面來獲取信息。 首先，你瀏覽一下針對所有 Web控件格式屬性他們是基本控件類的格式屬性。 寫驗(yàn)證代碼到客戶端代 碼中的優(yōu)勢能夠及時(shí)反饋到你的用戶。 然而，問題是它不與所有的瀏覽器兼容。就這樣的做法更有安全的保障。 如果一個瀏覽器不支持 JavaScript，那個驗(yàn)證規(guī)則會自動在服務(wù)器端代碼中執(zhí)行。 然而，這個控件也可以用在其他的輸入型控件，例如： 。 比較值 : CompareValidator 控件 這個 CompareValidator 控件用于比較一個輸入的數(shù)據(jù)和另外一個值是否相同。 幸好，微軟除了包含上面提到的控件還包括 ValidationSummary 控件。 瀏覽狀態(tài)的妙處是它不依賴 任何的特定服務(wù)器或?yàn)g覽器的屬性。 你能夠自動地保存頁面里的數(shù)據(jù)狀態(tài)。 你可能想要隱藏或者顯示完成依靠用戶參考的問題的詳細(xì)說明。 使用 Visible and Enabled屬性 每個控件 ,包括 HTML 和 Web控件 ,有一個 Visible 屬性來 決定那個控件是否可見。 使瀏覽狀態(tài)失效 在特定的環(huán)境中，你可能想要對一個單獨(dú)的控件或 一個整體的瀏覽狀態(tài)失效。