Hanselman's Early Asp.net Interview Questions

Front 1

general page life-cycle stages

Back 1

Page request

Start

Initialization

Load

Postback event handling

Rendering

Unload

Front 2

life-cycle events of a page

Back 2

PreInit

Init

InitComplete

PreLoad

Load

Control events

LoadComplete

PreRender

PreRenderComplete

SaveStateComplete

Render

Unload

Front 3

PreInit page event

Back 3

raised after the start stage is complete and before initialize stage begins (first event of the page)

use this event for the following:
1. check the isPostBack property to determine whether this is the first time the page is being processed
2. create or re-create dynamic controls
3. set a master page dynamically
4. set the Theme property dynamically
5. read or set profile property values

* if the request is a postback, the values of the controls have not yet been restored from the view state. If you set a control property at this stage, its value might be overwritten in the Init event

Front 4

Init page event

Back 4

raised after all controls have been initialized and any skin settings have been applied

the Init event of individual controls occurs before the Init event of the page, therefore, you can use this event to read or initialize control properties

Front 5

InitComplete page event

Back 5

raised at the end of the page's initialization stage

only one operation takes place between Init and InitComplete:
tracking of view state changes is turned on

use this event to make changes to view state that you want to make sure are persisted after the next postback

Front 6

view state tracking

Back 6

turned on between Init and InitComplete page events

enables controls to persist any values that are programmatically added to the ViewState collection

until view state tracking is turned on, any values added to view state are lost across postbacks

controls typically turn on view state tracking immediately after they raise their Init event

Front 7

PreLoad page event

Back 7

raised after the page loads view state for itself and all controls, and after it processes postback data that is included with the Request instance

Front 8

Load page event

Back 8

the Page object calls the OnLoad method on the Page object, and then recursively does the same for each child control until the page and all controls are loaded.

the Load event of individual controls occurs after the Load event of the page

use the OnLoad event method to set properties in controls and to establish database connections

Front 9

OnLoad event method

Back 9

use the OnLoad event method to set properties in controls and to establish database connections

Front 10

control events

Back 10

use these events to handle specific control events, such as a Button control's Click event or a TextBox control's TextChanged event

Front 11

LoadComplete page event

Back 11

raised at the end of the event-handling stage

use this event for tasks that require that all other controls on the page be loaded

Front 12

PreRender page event

Back 12

raised after the Page object has created all controls that are required in order to render the page, including child controls of composite controls

use this event to make final changes to the contents of the page or its controls before the rendering stage begins

Front 13

PreRenderComplete page event

Back 13

raised after each data bound control whose DataSourceID property is set calls its DataBind method

Front 14

SaveStateComplete page event

Back 14

raised after view state and control state have been saved for the page and for all controls

any changes to the page or controls at this point affect rendering, but the changes will not be retrieved on the next post back

Front 15

Render page event

Back 15

this is not an event - instead, at this stage of processing, the Page object calls this method on each control

all ASP.Net web server controls have a Render method that writes out the control's markup to send to the browser

Front 16

Unload page event

Back 16

raised for each control and then for the page

in controls, use this event to do final cleanup for specific controls, such as closing control-specific database connections

for the page itself, use this event to do final cleanup work, such as:
1. closing open files
2. closing open database connections
3. finishing up logging or other request-specific tasks

Front 17

what are ASHX files

Back 17

used to write custom httphandlers without the overhead of processing a page request (aspx file)

a placeholder for an HttpHandler which allows you to create an IHttpHandler implementation without any reconfiguration of web.config

it provides you access to the Request and Response without any of the facilities or overhead of the page model

Front 18

what are HttpHandlers

Back 18

low level implementations of the request/response http cycle

using an HttpHandler, you can deliver responses back to the browser with minimal overhead

Front 19

how are HttpHandlers configured?

Back 19

by registering them in web.config

you may also need to configure IIS to send certain file extension requests to aspnet_isapi.dll

Front 20

what are some uses of a handler file (.ashx)

Back 20

1. apply security mechanism
2. url rewriting
3. filter something in the request that is sent to IIS

Front 21

data binding events for data-bound controls

Back 21

1. Databinding

2. RowCreated (GridView only)
OR
ItemCreated (all other data controls)

3. RowDataBound (GridView only)
OR
ItemDataBound (all other data controls)

4. DataBound

Front 22

DataBinding event for data-bound controls

Back 22

raised after the control's PreRender event

this event marks the beginning of the process that binds the control to the data

USE: use this event to manually open database connections and to set parameter values dynamically before a query is run

Front 23

RowCreated or ItemCreated event for data-bound controls

Back 23

raised after the control's DataBinding event

USE: use this event to manipuluate content that is not dependent on data binding (i.e.: you might programmatically add formatting to a header or footer row in a GridView control)

Front 24

RowDataBound or ItemDataBound event for data-bound controls

Back 24

raised after the control's RowCreated or ItemCreated event

USE: when this event occurs, data is available in the row or item so you can format data or set the FilterExpression property on child data source controls

Front 25

DataBound event for data-bound controls

Back 25

raised at the end of data-binding operations in a data-bound control

USE: use this event to format data-bound content or to initiate data binding in other controls that depend on values from the current control's content

Front 26

PostBack

Back 26

the process of submitting an ASP.Net page to the server for processing (posting back to the server)

if a web page consists of one or more Web Controls configured to use AutoPostBack, the ASP.Net adds a special JavaScript function to the rendered HTML Page called _doPostBack()

Front 27

How do I chain my own JavaScript into the client side without losing PostBack functionality?

Back 27

you can use control events like OnClientClick to chain in your client side JavaScript, or you can use the GetPostBackEventReference method to give your scripts access to the postback method on the client side.

Front 28

what is ViewState

Back 28

the technique used by ASP.Net web pages to persist changes to the state of a Web Form across postbacks

Front 29

where is view state stored?

Back 29

by default it is placed in a hidden form field names __VIEWSTATE

the view state is serialized to the hidden form field and deserialized back on postback

Front 30

what is the drawback of ViewState?

Back 30

it is a hidden form filed which can easily get very larger causing slower downloads

whenever the user posts back the Web page, the contents of this hidden form field must be posted back in the HTTP request, thereby lengthening request time as well

Front 31

What happens when an HTTP request is received on a TCP/IP port

Back 31

when a web server receives a request, it examines the file name extension of the requested file, determines which ISAPI extension should handle the request and then passes the request to the appropriate ISAPI extension

Front 32

what is ASP.Net?

Back 32

an ISAPI extension under the Web server

Front 33

How does IIS communicate with ASP.Net

Back 33

When an aspx page is requested, IIS checks the file extension in its metabase.

aspx is mapped to aspnet_isapi.dll

When IIS find the extension aspx, then it loads the aspnet_isapi.dll and passes all the request details to it.

aspnet_isapi.dll then loads the CLR and passes all the request details that received.

CLR then create HttpRuntime engine.

The begining of the runtime engine is HttpRunTime class. It creates the HttpContext object and stores all the request details.

From there HttpContext object passes through a pipeline which consists of HttpApplication object, HttpModule objects and finally HttpHandler object.
HttpHandler object creates the html page.

Front 34

what is an assembly binding redirect

Back 34

you can redirect your app to use a different version of an assembly

how:
1. through a publisher policy
2. through an app configuration file
3. through a machine configuration file

Front 35

compare LoadLibrary(), CreateObject() and Assembly.Load()

Back 35

LoadLibrary() : loads the specified module into the address space of the calling process

CreateObject() : creates and returns a reference to an Automation object

Assembly.Load() : Loads an assembly

Front 36

What is the OO relationship between an ASPX page and its CS/VB code behind file

Back 36

inheritance
(the aspx simply inherits from the code behind class so that it can access protected methods)