What is the use of PlaceHolder control? Can we see it at runtime?

The PlaceHolder control acts as a container for those controls that are dynamically generated at runtime. We cannot see it at runtime because it does not produce any visible output. It used only as a container.

Explain login controls.

Login controls are built-in controls in ASP.Net for providing a login solution to ASP.NET application. The login controls use the membership system to authenticate a user credentials for a Web site.

There are many controls in login controls.

• ChangePassword control - Allows users to change their password.
• CreateUserWizard control - Provides an interface to the user to register for that Web site.
• Login control - Provides an interface for user authentication. It consists of a set of controls, such as TextBox, Label, Button, CheckBox, HyperLink.
• LoginView control - Displays appropriate information to different users according to the user's status.
• LoginStatus control - Shows a login link to users, who are not authenticated and logout link, who are authenticated
• LoginName control - Displays a user name, if the user logs in.
• PasswordRecovery control - Allows users to get back the password through an e-mail, if they forget. 

Explain how Cookies work. Give an example of Cookie abuse.

The server tells the browser to put some files in a cookie, and the client then sends all the cookies for the domain in each request. An example of cookie abuse is large cookies affecting the network traffic.

How can you implement the postback property of an ASP.NET control?

You need to set the AutoPostBack property to True to implement the PostBack property of controls.

Explain file-based dependency and key-based dependency

In file-based dependency, you have to depend on a file that is saved in a disk. In key-based dependency, you have to depend on another cached item.

What are the events that happen when a client requests an ASP.NET page from IIS server?

The following events happen when a client requests an ASP.NET page from the IIS server:

1. User requests for an application resource.
2. The integrated request-processing pipeline receives the first user request.
3. Response objects are created for each user request.
4. An object of the HttpApplication class is created and allocated to the Request object.
5. The HttpApplication class processes the user request. 

What are HTTP handlers in ASP.NET?

HTTP handlers, as the name suggests, are used to handle user requests for Web application resources. They are the backbone of the request-response model of Web applications. There is a specific event handler to handle the request for each user request type and send back the corresponding response object.

Each user requests to the IIS Web server flows through the HTTP pipeline, which refers to a series of components (HTTP modules and HTTP handlers) to process the request. HTTP modules act as filters to process the request as it passes through the HTTP pipeline. The request, after passing through the HTTP modules, is assigned to an HTTP handler that determines the response of the server to the user request. The response then passes through the HTTP modules once again and is then sent back to the user.

You can define HTTP handlers in the <httpHandlers> element of a configuration file. The <add> element tag is used to add new handlers and the <remove> element tag is used to remove existing handlers. To create an HTTP handler, you need to define a class that implements the IHttpHandler interface.

What is the default timeout for a Cookie?

The default time duration for a Cookie is 30 minutes.

Suppose you want an ASP.NET function (client side) executed on the MouseOver event of a button. Where do you add an event handler?

The event handler is added to the Add() method of the Attributes property.

How does a content page differ from a master page?

A content page does not have complete HTML source code; whereas a master page has complete HTML source code inside its source file.