11基本ASP.NET面试问题 *

程序员附加了回发事件处理程序，例如，使用 AutoPostBack 控件的属性. A small bit of JavaScript in the page causes it to submit the form when the control loses focus (or when the value changes, 比如用下拉控件). The server then invokes the event handler, which re-renders the page back to the browser.

一种替代方法是部分回发，使用名为an的控件 UpdatePanel. 用这种技术, AJAX用于从客户机向服务器发出单独的请求, 哪一个不提交整个表格. 响应只重新呈现有问题的面板，而不是整个页面.

第二种技术是绕过原生ASP.NET and write your own JavaScript code using jQuery or another way of supporting AJAX.

ASP.. NET使用一个称为 code behind 允许所有HTML标记在视图文件中(使用 .aspx 扩展)，而行为是在单独的c#类(类)中定义的 后台代码的类, with the .aspx.cs extension). JavaScript通常也作为单独的文件提供.

Keeping things separate allows the person responsible for visual layout to only touch that file, 而另一个人可能负责c#中的编码行为. 布局和行为可以独立改变而不会相互影响. ASP.NET鼓励(但不强制)以这种方式进行分离.

一种技术被称为 view state. 当你使用viewstate, the collection of server-side state variables gets serialized and sent to a hidden client-side form field. 当表单提交回服务器时, the serialized string is re-inflated to form the collection of server-side state variables.

另一个技巧是 会话状态. The collection of objects associated with a user session is persisted in server memory or a database, 客户端cookie用于将每个用户会话映射到集合.

It is possible to interleave all three kinds of code in one file, even in the same line of code. Notwithstanding the reasons to keep them separate, there are also some reasons to combine them.

一个原因是能够在HTML中直接包含服务器计算的值. 这个例子展示了HTML中的c#表达式:

Today is <%=DateTime.Today.Format("M d, yyyy")%>

另一个原因是将服务器计算的值注入到JavaScript中. 这个c#示例导致浏览器在一秒钟后跳转到一个新页面:

Response.Write("");

Visual Studio分析 .aspx page and auto-generates the declarations into another file—one which is rarely inspected by developers. The declarations are part of the same class using the mechanism of partial classes.

服务器端框架: .NET是微软一系列框架的名字. ASP.. NET是web相关技术的集合 .NET. Web Forms is a subset of that collection, encapsulating a particular programming model.

Tiers:在应用程序架构中有多个层次. 其中最常见的三个是数据库服务器, 应用程序服务器, 浏览器(也称为客户端).

通信协议层间通信的契约或风格. HTTP(或HTTPS)是客户机和应用服务器之间使用的协议.

序列化格式:数据如何在字节流和字节流之间转换. 格式包括JSON、二进制、XML和Base64(这些可以组合在一起). These are open to interpretation, and some can also be considered encoding schemes.

编程语言:数据库服务器通常使用SQL语言. 应用层使用c#或Visual Basic语言(通常不混合使用)。. 浏览器使用JavaScript语言.

客户端框架: The browser tier may use code libraries or frameworks, which usually consist of JavaScript and CSS. 列出的客户端框架是jQuery和Bootstrap.

Techniques: These items each involve different combinations of concepts mentioned above: AJAX, postback, 和验证.

Note申请人不需要得出与这个列表完全相同的结论, 因为在术语上有一些歧义. However a discussion of these points can yield insight into the applicant’s thought process.

对于页眉和页脚，您可以使用母版页来定义模板. Then each content page can refer to the master page instead of repeating the header and footer.

For the few pages that need a condensed header, you can use a separate master page.

对于捐赠按钮，您将使用用户控件.

A careless programmer forgot to URL-encode the URL in the “href” property of the link. 例如，链接可能在最终的HTML中被错误地呈现为:

Detail for Wiley & Sons

但是，服务器会解释 & 字符作为URL参数之间的分隔符. 正确的url编码版本如下:

Detail for Wiley & Sons

There are several statements that show the tester is not understanding the situation very well:

• 浏览器几乎不会直接与数据库通信.
• The HTTP PUT 动词不太可能与ASP一起使用.NET网页表格.
• 这不太可能是数据库错误，因为:
  1. It is possible, but unusual, to implement phone number formatting at the database level
  2. 如果它是在那个层次上实施的, it would be unlikely to break in a manner that would allow some misformatted values into the database
  3. 错误消息看起来不像数据库服务器发出的消息

错误消息表明服务器和/或客户端存在代码错误, 哪个更可能与电话号码验证功能相关. 具体来说，可能是检查失败 -1 的结果 IndexOf 方法(或 indexOf 在JavaScript中).

The reason is most likely that a postback event was added to the client dropdown, 导致页面刷新, 但是复选框的视图状态没有正确地进行往返. 也就是说, 这些值没有包含在提交给服务器回发的表单中, 和/或在页面刷新期间不重新渲染.

There are a couple complications with the page’s requirements that make this scenario likely:

1. Checkboxes only send values to the server when checked and are simply omitted when cleared. 所有其他输入类型总是发送值.
2. When a page requires a variable-length list of controls, it becomes harder to stay within the ASP.. NET编程模型, so programmers might resort to emitting the controls by code in a manner that does not participate in the round-tripping of values.