.NET Interview Questions – Part 13
1.What’s a bubbled event?
When you have a complex control, like DataGrid, writing an event processing routine for each object (cell, button, row, etc.) is quite tedious. The controls can bubble up their event handlers, allowing the main DataGrid event handler to take care of its constituents.
2.Suppose you want a certain ASP.NET function executed on MouseOver for a certain button. Where do you add an event handler?
Add an OnMouseOver attribute to the button. Example: btnSubmit.Attribute s.Add(“onmouseov er”,”someClientC odeHere() ;”);
3.What data types do the RangeValidator control support?
Integer, String, and Date.
4.When during the page processing cycle is ViewState available?
After the Init() and before the Page_Load(), or OnLoad() for a control.
5.What namespace does the Web page belong in the .NET Framework class hierarchy?
6. Where do you store the information about the user’s locale?
7. What’s the difference between Codebehind=” MyCode.aspx. cs” and Src=”MyCode. aspx.cs”?
CodeBehind is relevant to Visual Studio.NET only.
8.Explain the differences between Server-side and Client-side code?
Server-side code executes on the server. Client-side code executes in the client’s browser.
9. What type of code (server or client) is found in a Code-Behind class?
10. Should user input data validation occur server-side or client-side? Why?
All user input data validation should occur on the server at a minimum. Additionally, client-side validation can be performed where deemed appropriate and feasable to provide a richer, more responsive experience for the user.
11. What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?
Server.Transfer transfers page processing from one page directly to the next page without making a round-trip back to the client’s browser. This provides a faster response with a little less overhead on the server. Server.Transfer does not update the clients url history list or current url. Response.Redirect is used to redirect the user’s browser to another page or site. This perform as a trip back to the client where the client’s browser is redirected to the new page. The user’s browser history list is updated to reflect the new address.
12.Describe the role of inetinfo.exe, aspnet_isapi. dll and aspnet_wp.exe in the page loading process ?
inetinfo.exe is the Microsoft IIS server running, handling ASP.NET requests among other things. When an ASP.NET request is received (usually a file with .aspx extension), the ISAPI filter aspnet_isapi. dll takes care of it by passing the request to the actual worker process aspnet_wp.exe.
13. What’s the difference between Response.Write( ) and Response.Output. Write()?
Response.Output. Write() allows you to write formatted output.
14. What methods are fired during the page load?
Init() – when the page is instantiated
Load() – when the page is loaded into server memory
PreRender() – the brief moment before the page is displayed to the user as HTML
Unload() – when page finishes loading.
15. Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?
· A DataSet can represent an entire relational database in memory, complete with tables, relations, and views.
· A DataSet is designed to work without any continuing connection to the original data source.
· Data in a DataSet is bulk-loaded, rather than being loaded on demand.
· There’s no concept of cursor types in a DataSet.
· DataSets have no current record pointer You can use For Each loops to move through the data.
· You can store many edits in a DataSet, and write them to the original data source in a single operation.
· Though the DataSet is universal, other objects in ADO.NET come in different versions for different data sources.
16. What is the Global.asax used for?
The Global.asax (including the Global.asax. cs file) is used to implement application and session level events.
17. What are the Application_ Start and Session_Start subroutines used for?
This is where you can set the specific variables for the Application and Session objects.
18. Which method do you invoke on the DataAdapter control to load your generated dataset with data?
The Fill() method.
19. Can you edit data in the Repeater control?
No, it just reads the information from its data source.
20. Which template must you provide, in order to display data in a Repeater control?
21. How can you provide an alternating color scheme in a Repeater control?
Use the AlternatingItemTemp late.
22. What property must you set, and what method must you call in your code, in order to bind the data from a data source to the Repeater control?
You must set the DataSource property and call the DataBind method.
23. What base class do all Web Forms inherit from?
The Page class.
24. Name two properties common in every validation control?
ControlToValidate property and Text property.
25. Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box?
26. Which control would you use if you needed to make sure the values in two different controls matched?
27. Can you explain what inheritance is and an example of when you might use it?
When you want to inherit (use the functionality of) another class. Example: With a base class named Employee, a Manager class could be derived from the Employee base class.
28. Whats an assembly?
Assemblies are the building blocks of the .NET framework.
29. Describe the difference between inline and code behind.
Inline code written along side the html in a page. Code-behind is code written in a separate file and referenced by the .aspx page.
30. Explain what a diffgram is, and a good use for one?
The DiffGram is one of the two XML formats that you can use to render DataSet object contents to XML. A good use is reading database data to an XML file to be sent to a Web Service.
31. Whats MSIL, and why should my developers need an appreciation of it if at all?
MSIL is the Microsoft Intermediate Language. All .NET compatible languages will get converted to MSIL. MSIL also allows the .NET Framework to JIT compile the assembly on the installed computer.
32. How many classes can a single .NET DLL contain?
It can contain many classes.
33. What is ViewState?
ViewState allows the state of objects (serializable) to be stored in a hidden field on the page. ViewState is transported to the client and back to the server, and is not stored on the server or any other external source. ViewState is used to retain the state of server-side objects between post backs.
34. What is CLS (Common Language Specificaiton) ?
It provides the set of specificaiton which has to be adhered by any new language writer / Compiler writer for .NET Framework. This ensures Interoperability. For example: Within a ASP.NET application written in C#.NET language, we can refer to any DLL written in any other language supported by .NET Framework. As of now .NET Supports around 32 languages.
35. What is CTS (Common Type System)?
It defines about how Objects should be declard, defined and used within .NET. CLS is the subset of CTS.
36. What is Boxing and UnBoxing?
Boxing is implicit conversion of ValueTypes to Reference Types (Object). UnBoxing is explicit conversion of Reference Types (Object) to its equivalent ValueTypes. It requires type-casting.
37.. What is the difference between Value Types and Reference Types?
Value Types uses Stack to store the data where as the later uses the Heap to store the data.
38. What is the lifespan for items stored in ViewState?
Item stored in ViewState exist for the life of the current page. This includes postbacks (to the same page).
39. What does the “EnableViewState” property do? Why would I want it on or off?
It allows the page to save the users input on a form across postbacks. It saves the server-side values for a given control into ViewState, which is stored as a hidden value on the page before sending the page to the clients browser. When the page is posted back to the server the server control is recreated with the state stored in viewstate.
40. What are the different types of Session state management options available with ASP.NET?
ASP.NET provides In-Process and Out-of-Process state management. In-Process stores the session in memory on the web server. This requires the a “sticky-server” (or no load-balancing) so that the user is always reconnected to the same web server. Out-of-Process Session state management stores data in an external data source. The external data source may be either a SQL Server or a State Server service. Out-of-Process state management requires that all objects stored in session are serializable.
41. What are the different types of assemblies available and their purpose?
Private, Public/shared and Satellite Assemblies.
Private Assemblies : Assembly used within an application is known as private assemblies.
Public/shared Assemblies : Assembly which can be shared across applicaiton is known as shared assemblies. Strong Name has to be created to create a shared assembly. This can be done using SN.EXE. The same has to be registered using GACUtil.exe (Global Assembly Cache).
Satellite Assemblies : These assemblies contain resource files pertaining to a locale (Culture+Language) . These assemblies are used in deploying an Gloabl applicaiton for different languages.
42. What is view state and use of it?
The current property settings of an ASP.NET page and those of any ASP.NET server controls contained within the page. ASP.NET can detect when a form is requested for the first time versus when the form is posted (sent to the server), which allows you to program accordingly.
43. What are user controls and custom controls?
Custom controls: A control authored by a user or a third-party software vendor that does not belong to the .NET Framework class library. This is a generic term that includes user controls. A custom server control is used in Web Forms (ASP.NET pages). A custom client control is used in Windows Forms applications.
User Controls: In ASP.NET: A user-authored server control that enables an ASP.NET page to be re-used as a server control. An ASP.NET user control is authored declaratively and persisted as a text file with an .ascx extension. The ASP.NET page framework compiles a user control on the fly to a class that derives from the System.Web.UI. UserControl class.
44. What are the validation controls?
A set of server controls included with ASP.NET that test user input in HTML and Web server controls for programmer-defined requirements. Validation controls perform input checking in server code. If the user is working with a browser that supports DHTML, the validation controls can also perform validation using client script.
45. What’s the difference between Response.Write( ) andResponse. Output.Write( )?
The latter one allows you to write formattedoutput.
46. What are the different types of caching?
Caching is a technique widely used in computing to increase performance by keeping frequently accessed or expensive data in memory. In context of web application, caching is used to retain the pages or data across HTTP requests and reuse them without the expense of recreating them. ASP.NET has 3 kinds of caching strategies Output Caching, Fragment Caching, Data Caching.
Output Caching: Caches the dynamic output generated by a request. Some times it is useful to cache the output of a website even for a minute, which will result in a better performance. For caching the whole page the page should have OutputCache directive.<%@ OutputCache Duration=”60″ VaryByParam= “state” %>
Fragment Caching: Caches the portion of the page generated by the request. Some times it is not practical to cache the entire page, in such cases we can cache a portion of page<%@ OutputCache Duration=”120″ VaryByParam= “CategoryID; SelectedID” %>
Data Caching: Caches the objects programmatically. For data caching asp.net provides a cache object for eg: cache[“States” ] = dsStates;
47. What do you mean by authentication and authorization?
Authentication is the process of validating a user on the credentials (username and password) and authorization performs after authentication. After Authentication a user will be verified for performing the various tasks, Its access is limited it is known as authorization.
48. What are different types of directives in .NET?
@Page: Defines page-specific attributes used by the ASP.NET page parser and compiler. Can be included only in .aspx files <%@ Page AspCompat=”TRUE” language=”C# ” %>
@Control:Defines control-specific attributes used by the ASP.NET page parser and compiler. Can be included only in .ascx files. <%@ Control Language=”VB” EnableViewState= “false” %>
@Import: Explicitly imports a namespace into a page or user control. The Import directive cannot have more than one namespace attribute. To import multiple namespaces, use multiple @Import directives. <% @ Import Namespace=”System. web” %>
@Implements: Indicates that the current page or user control implements the specified .NET framework interface.<%@ Implements Interface=”System. Web.UI.IPostBack EventHandler” %>
@Register: Associates aliases with namespaces and class names for concise notation in custom server control syntax.<%@ Register Tagprefix=”Acme” Tagname=”AdRotator” Src=”AdRotator. ascx” %>
@Assembly: Links an assembly to the current page during compilation, making all the assembly’s classes and interfaces available for use on the page. <%@ Assembly Name=”MyAssembly” %> <%@Assembly Src=”MySource. vb” %>
@OutputCache: Declaratively controls the output caching policies of an ASP.NET page or a user control contained in a page<%@ OutputCache Duration=”#ofsecond s” Location=”Any | Client | Downstream | Server | None” Shared=”True | False” VaryByControl= “controlname” VaryByCustom= “browser | customstring” VaryByHeader= “headers” VaryByParam= “parametername” %>
@Reference: Declaratively indicates that another user control or page source file should be dynamically compiled and linked against the page in which this directive is declared.
49. How do I debug an ASP.NET application that wasn’t written with Visual Studio.NET and that doesn’t use code-behind?
Start the DbgClr debugger that comes with the .NET Framework SDK, open the file containing the code you want to debug, and set your breakpoints. Start the ASP.NETapplication. Go back to DbgClr, choose Debug Processes from the Tools menu, and select aspnet_wp.exe from the list of processes. (If aspnet_wp.exe doesn’t appear in the list,check the “Show system processes” box.) Click the Attach button to attach to aspnet_wp.exe and begin debugging.
Be sure to enable debugging in the ASPX file before debugging it with DbgClr. You can enable tell ASP.NET to build debug executables by placing a
<%@ Page Debug=”true” %> statement at the top of an ASPX file or a <COMPILATION debug=”true” />statement in a Web.config file.
50. Can a user browsing my Web site read my Web.config or Global.asax files?
No. The <HTTPHANDLERS>section of Machine.config, which holds the master configuration settings forASP.NET, contains entries that map ASAX files, CONFIG files, and selected other file types to an HTTP handler named HttpForbiddenHandle r, which fails attempts to retrieve the associated file. You can modify it by editing Machine.config or including an section in a local Web.config file.
51. What methods are fired during the page load? Init()
When the page is instantiated, Load() – when the page is loaded into server memory,PreRender () – the brief moment before the page is displayed to the user as HTML, Unload() – when page finishes loading.
52. Where does the Web page belong in the .NET Framework class hierarchy?
53. Where do you store the information about the user’s locale?
54. What’s the difference between Codebehind=” MyCode.aspx. cs” and Src=”MyCode. aspx.cs”?
CodeBehind is relevant to Visual Studio.NET only.
55. What’s a bubbled event?
When you have a complex control, likeDataGrid, writing an event processing routine for each object (cell, button,row, etc.) is quite tedious. The controls can bubble up their eventhandlers, allowing the main DataGrid event handler to take care of its constituents. Suppose you want a certain ASP.NET function executed on MouseOver over a certain button.
56. Where do you add an event handler?
It’s the Attributesproperty, the Add function inside that property. e.g. btnSubmit.Attribute s.Add(“onMouseOv er”,”someClientC ode();”)
57. What data type does the RangeValidator control support?
Integer,String and Date.
58. What’s the difference between Page.RegisterClient ScriptBlock and Page.RegisterStartu pScript?
RegisterClientScrip tBlock is for returning blocks of client-side script containing functions. RegisterStartupScri pt is for returning blocks of client-script not packaged in functions-in other words, code that’s to execute when the page is loaded. The latter positions script blocks near the end of the document so elements on the page that the script interacts are loaded before the script runs.<%@ Reference Control=”MyControl. ascx” %>
59. Is it necessary to lock application state before accessing it?
Only if you’re performing a multistep update and want the update to be treated as an atomic operation. Here’s an example:
Application. Lock ();
Application[ “ItemsSold” ] = (int) Application[ “ItemsSold” ] + 1;
Application[ “ItemsLeft” ] = (int) Application[ “ItemsLeft” ] – 1;
Application. UnLock ();
By locking application state before updating it and unlocking it afterwards, you ensure that another request being processed on another thread doesn’t read application state at exactly the wrong time and see an inconsistent view of it. If I update session state, should I lock it, too? Are concurrent accesses by multiple requests executing on multiple threads a concern with session state? Concurrent accesses aren’t an issue with session state, for two reasons. One, it’s unlikely that two requests from the same user will overlap. Two, if they do overlap, ASP.NET locks down session state during request processing so that two threads can’t touch it at once. Session state is locked down when the HttpApplication instance that’s processing the request fires an AcquireRequestState event and unlocked when it fires a ReleaseRequestState event.
Do ASP.NET forms authentication cookies provide any protection against replay attacks? Do they, for example, include the client’s IP address or anything else that would distinguish the real client from an attacker?
No. If an authentication cookie is stolen, it can be used by an attacker. It’s up to you to prevent this from happening by using an encrypted communications channel (HTTPS). Authentication cookies issued as session cookies, do, however,include a time-out valid that limits their lifetime. So a stolen session cookie can only be used in replay attacks as long as the ticket inside the cookie is valid. The default time-out interval is 30 minutes.You can change that by modifying the timeout attribute accompanying the <forms> element in Machine.config or a local Web.config file. Persistent authentication cookies do not time-out and therefore are a more serious security threat if stolen.
60. How do I send e-mail from an ASP.NET application?
MailMessage message = new MailMessage ();
message.From = <email>;
message.To = <email>;
message.Subject = “Scheduled Power Outage”;
message.Body = “Our servers will be down tonight.”;
SmtpMail.SmtpServer = “localhost”;
MailMessage and SmtpMail are classes defined in the .NET Framework Class Library’s System.Web.Mail namespace. Due to a security change made to ASP.NET just before it shipped, you need to set SmtpMail’s SmtpServer property to “localhost” even though “localhost” is the default. In addition, you must use the IIS configuration applet to enable localhost (127.0.0.1) to relay messages through the local SMTP service.
61. What are VSDISCO files?
VSDISCO files are DISCO files that support dynamic discovery of Web services. If you place the following VSDISCO file in a directory on your Web server, for example, it returns references to all ASMX and DISCO files in the host directory and any subdirectories not noted in <exclude> elements:
<?xml version=”1.0″ ?>
xmlns=”urn:schemas- dynamicdiscovery :disco.2000- 03-17″>
<exclude path=”_vti_cnf” />
<exclude path=”_vti_pvt” />
<exclude path=”_vti_log” />
<exclude path=”_vti_script” />
<exclude path=”_vti_txt” />
62. How does dynamic discovery work?
ASP.NET maps the file name extension VSDISCO to an HTTP handler that scans the host directory and subdirectories for ASMX and DISCO files and returns a dynamically generated DISCO document. A client who requests a VSDISCO file gets back what appears to be a static DISCO document.
Note that VSDISCO files are disabled in the release version of ASP.NET. You can reenable them by uncommenting the line in the <httpHandlers> section of Machine.config that maps *.vsdisco to System.Web.Services .Discovery. DiscoveryRequest Handler and granting the ASPNET user account permission to read the IIS metabase. However, Microsoft is actively discouraging the use of VSDISCO files because they could represent a threat to Web server security.
63. Is it possible to prevent a browser from caching an ASPX page? Just call SetNoStore on the HttpCachePolicy object exposed through the Response object’s Cache property, as demonstrated here:
<%@ Page Language=”C# ” %>
Response.Cache. SetNoStore ();
Response.Write (DateTime.Now. ToLongTimeString ());
SetNoStore works by returning a Cache-Control: private, no-store header in the HTTP response. In this example, it prevents caching of a Web page that shows the current time.
64. What does AspCompat=”true” mean and when should I use it?
AspCompat is an aid in migrating ASP pages to ASPX pages. It defaults to false but should be set to true in any ASPX file that creates apartment-threaded COM objects–that is, COM objects registered ThreadingModel= Apartment. That includes all COM objects written with Visual Basic 6.0. AspCompat should also be set to true (regardless of threading model) if the page creates COM objects that access intrinsic ASP objects such as Request and Response. The following directive sets AspCompat to true:
<%@ Page AspCompat=”true” %>
Setting AspCompat to true does two things. First, it makes intrinsic ASP objects available to the COM components by placing unmanaged wrappers around the equivalent ASP.NETobjects. Second, it improves the performance of calls that the page places to apartment- threaded COM objects by ensuring that the page (actually, the thread that processes the request for the page) and the COM objects it creates share an apartment. AspCompat=”true” forces ASP.NET request threads into single-threaded apartments (STAs). If those threads create COM objects marked ThreadingModel= Apartment, then the objects are created in the same STAs as the threads that created them. Without AspCompat=”true, ” request threads run in a multithreaded apartment (MTA) and each call to an STA-based COM object incurs a performance hit when it’s marshaled across apartment boundaries.
Do not set AspCompat to true if your page uses no COM objects or if it uses COM objects that don’t access ASP intrinsic objects and that are registered ThreadingModel= Free or ThreadingModel= Both.
65. Explain the differences between Server-side and Client-side code?
66. What type of code (server or client) is found in a Code-Behind class?
67. Should validation (did the user enter a real date) occur server-side or client-side? Why?
Client-side validation because there is no need to request a server side date when you could obtain a date from the client machine.
68. What are ASP.NET Web Forms? How is this technology different than what is available though ASP?
Web Forms are the heart and soul of ASP.NET. Web Forms are the User Interface (UI) elements that give your Web applications their look and feel. Web Forms are similar to Windows Forms in that they provide properties, methods, and events for the controls that are placed onto them. However, these UI elements render themselves in the appropriate markup language required by the request, e.g. HTML. If you use Microsoft Visual Studio .NET, you will also get the familiar drag-and-drop interface used to create your UI for your Web application.
69. What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?
In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they’re difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems.
As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.
70. How can you provide an alternating color scheme in a Repeater control?
AlternatingItemTemp late Like the ItemTemplate element, but rendered for every other row (alternating items) in the Repeater control. You can specify a different appearance for the AlternatingItemTemp late element by setting its style properties.
71. Which template must you provide, in order to display data in a Repeater control?
72. What event handlers can I include in Global.asax?
Application_ Start,Applicatio n_End, Application_ AcquireRequestSt ate, Application_ AuthenticateRequ est, Application_ AuthorizeRequest , Application_ BeginRequest, Application_ Disposed, Application_ EndRequest, Application_ Error, Application_ PostRequestHandl erExecute, Application_ PreRequestHandle rExecute,
Application_ PreSendRequestCo ntent, Application_ PreSendRequestHe aders, Application_ ReleaseRequestSt ate, Application_ ResolveRequestCa che, Application_ UpdateRequestCac he, Session_Start, Session_End
You can optionally include “On” in any of method names. For example, you can name a BeginRequest event handler.Application _BeginRequest or Application_ OnBeginRequest. You can also include event handlers in Global.asax for events fired by custom HTTP modules.Note that not all of the event handlers make sense for Web Services (they’re designed forASP.NET applications in general, whereas .NET XML Web Services are specialized instances of an ASP.NET app). For example, the Application_ AuthenticateRequ est and Application_ AuthorizeRequest events are designed to be used with ASP.NET Forms authentication.
73. What is different b/w webconfig.xml & Machineconfig. xml?
Web.config & machine.config both are configuration files.Web.config contains settings specific to an application where as machine.config contains settings to a computer. The Configuration system first searches settings in machine.config file & then looks in application configuration files.Web.config, can appear in multiple directories on an ASP.NET Web application server. Each Web.config file applies configuration settings to its own directory and all child directories below it. There is only Machine.config file on a web server.
If I’m developing an application that must accomodate multiple security levels though secure login and my ASP.NET web appplication is spanned across three web-servers (using round-robbin load balancing) what would be the best approach to maintain login-in state for the users?
Use the state server or store the state in the database. This can be easily done through simple setting change in the web.config.
StateConnectionStri ng=”tcpip= 127.0.0.1: 42424″
sqlConnectionString =”data source=127.0. 0.1; user id=sa; password=”
You can specify mode as “stateserver” or “sqlserver”.
Where would you use an iHTTPModule, and what are the limitations of any approach you might take in implementing one
“One of ASP.NET’s most useful features is the extensibility of the HTTP pipeline, the path that data takes between client and server. You can use them to extend your ASP.NETapplications by adding pre- and post-processing to each HTTP request coming into your application. For example, if you wanted custom authentication facilities for your application, the best technique would be to intercept the request when it comes in and process the request in a custom HTTP module.
74. How do you turn off cookies for one page in your site?
Since no Page Level directive is present, I am afraid that cant be done.
75. How do you create a permanent cookie?
Permanent cookies are available until a specified expiration date, and are stored on the hard disk.So Set the ‘Expires’ property any value greater than DataTime.MinValue with respect to the current datetime. If u want the cookie which never expires set its Expires property equal to DateTime.maxValue.
76. Which method do you use to redirect the user to another page without performing a round trip to the client?
Server.Transfer and Server.Execute
77. What property do you have to set to tell the grid which page to go to when using the Pager object?
78. Should validation (did the user enter a real date) occur server-side or client-side? Why?
It should occur both at client-side and Server side.By using expression validator control with the specified expression ie.. the regular expression provides the facility of only validatating the date specified is in the correct format or not. But for checking the date where it is the real data or not should be done at the server side, by getting the system date ranges and checking the date whether it is in between that range or not.
79. What does the “EnableViewState” property do? Why would I want it on or off?
Enable ViewState turns on the automatic state management feature that enables server controls to re-populate their values on a round trip without requiring you to write any code. This feature is not free however, since the state of a control is passed to and from the server in a hidden form field. You should be aware of when ViewState is helping you and when it is not. For example, if you are binding a control to data on every round trip, then you do not need the control to maintain it’s view state, since you will wipe out any re-populated data in any case. ViewState is enabled for all server controls by default. To disable it, set the EnableViewState property of the control to false.
80. What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?
Server.Transfer( ) : client is shown as it is on the requesting page only, but the all the content is of the requested page. Data can be persist accros the pages using Context.Item collection, which is one of the best way to transfer data from one page to another keeping the page state alive.
Response.Dedirect( ) :client know the physical location (page name and query string as well). Context.Items loses the persisitance when nevigate to destination page. In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they’re difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems. As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.
81. Can you give an example of when it would be appropriate to use a web service as opposed to a non-serviced .NET component?
Communicating through a Firewall When building a distributed application with 100s/1000s of users spread over multiple locations, there is always the problem of communicating between client and server because of firewalls and proxy servers. Exposing your middle tier components as Web Services and invoking the directly from a Windows UI is a very valid option.
Application Integration When integrating applications written in various languages and running on disparate systems. Or even applications running on the same platform that have been written by separate vendors.
Business-to- Business Integration This is an enabler for B2B intergtation which allows one to expose vital business processes to authorized supplier and customers. An example would be exposing electronic ordering and invoicing, allowing customers to send you purchase orders and suppliers to send you invoices electronically.
Software Reuse This takes place at multiple levels. Code Reuse at the Source code level or binary componet-based resuse. The limiting factor here is that you can reuse the code but not the data behind it. Webservice overcome this limitation. A scenario could be when you are building an app that aggregates the functionality of serveral other Applicatons. Each of these functions could be performed by individual apps, but there is value in perhaps combining the the multiple apps to present a unifiend view in a Portal or Intranet.
When not to use Web Services: Single machine Applicatons When the apps are running on the same machine and need to communicate with each other use a native API. You also have the options of using component technologies such as COM or .NET Componets as there is very little overhead.
Homogeneous Applications on a LAN If you have Win32 or Winforms apps that want to communicate to their server counterpart. It is much more efficient to use DCOM in the case of Win32 apps and .NET Remoting in the case of .NET Apps
82. Can you give an example of what might be best suited to place in the Application_ Start and Session_Start subroutines?
The Application_ Start event is guaranteed to occur only once throughout the lifetime of the application. It’s a good place to initialize global variables. For example, you might want to retrieve a list of products from a database table and place the list in application state or the Cache object. SessionStateModule exposes both Session_Start and Session_End events.
83. What are the advantages and disadvantages of viewstate?
The primary advantages of the ViewState feature in ASP.NET are:
1. Simplicity. There is no need to write possibly complex code to store form data between page submissions.
2. Flexibility. It is possible to enable, configure, and disable ViewState on a control-by-control basis, choosing to persist the values of some fields but not others.
There are, however a few disadvantages that are worth pointing out:
1. Does not track across pages. ViewState information does not automatically transfer from page to page. With the session
approach, values can be stored in the session and accessed from other pages. This is not possible with ViewState, so storing
data into the session must be done explicitly.
2. ViewState is not suitable for transferring data for back-end systems. That is, data still has to be transferred to the back
end using some form of data object.
84. Describe session handling in a webfarm, how does it work and what are the limits? ASP.NET Session supports storing of session data in 3 ways, i] in In-Process ( in the same memory that ASP.NET uses) , ii] out-of-process using Windows NT Service )in separate memory from ASP.NET ) or iii] in SQL Server (persistent storage). Both the Windows Service and SQL Server solution support a webfarm scenario where all the web-servers can be configured to share common session state store.
1. Windows Service : We can start this service by Start | Control Panel | Administrative Tools | Services | . In that we service names ASP.NET State Service. We can start or stop service by manually or configure to start automatically. Then we have to configure our web.config file
mode = “StateServer”
stateConnectionStri ng = “tcpip=127.0. 0.1:42424”
stateNetworkTimeout = “10”
sqlConnectionString =”data source = 127.0.0.1; uid=sa;pwd=”
timeout= “20” />
Here ASP.Net Session is directed to use Windows Service for state management on local server (address : 127.0.0.1 is TCP/IP loop-back address). The default port is 42424. we can configure to any port but for that we have to manually edit the registry.
Follow these simple steps
– In a webfarm make sure you have the same config file in all your web servers.
– Also make sure your objects are serializable.
– For session state to be maintained across different web servers in the webfarm, the application path of the web-site in the IIS Metabase should be identical in all the web-servers in the webfarm.
85. Which template must you provide, in order to display data in a Repeater control?
You have to use the ItemTemplate to Display data. Syntax is as follows,
< ItemTemplate >
< div class =”rItem” >
< img src=”images/<%# Container.DataItem(“ ImageURL”) %>” hspace=”10” />
< b > <% # Container.DataItem(“ Title”)%>
< /div >
< ItemTemplate >
How can you provide an alternating color scheme in a Repeater control?
Using the AlternatintItemTemp late
86. What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeater control?
Set the DataMember property to the name of the table to bind to. (If this property is not set, by default the first table in the dataset is used.) DataBind method, use this method to bind data from a source to a server control. This method is commonly used after retrieving a data set through a database query.
87. What method do you use to explicitly kill a user s session?
You can dump (Kill) the session yourself by calling the method Session.Abandon.
ASP.NET automatically deletes a user’s Session object, dumping its contents, after it has been idle for a configurable timeout interval. This interval, in minutes, is set in the <SESSIONSTATE>section of the web.config file. The default is 20 minutes.
88. How do you turn off cookies for one page in your site?
Use Cookie.Discard property, Gets or sets the discard flag set by the server. When true, this property instructs the client application not to save the Cookie on the user’s hard disk when a session ends.
89. Which two properties are on every validation control?
We have two common properties for every validation controls
1. Control to Validate,
2. Error Message.
90. What tags do you need to add within the asp:datagrid tags to bind columns manually?
< asp:DataGrid id=”dgCart” AutoGenerateColumns =”False” CellPadding= “4” Width=”448px” runat=”server” >
< Columns >
< asp:ButtonColumn HeaderText=” SELECT” Text=”SELECT” CommandName= “select” >< /asp:ButtonColumn >
< asp:BoundColumn DataField=”ProductI d” HeaderText=” Product ID” > < /asp:BoundColumn >
< asp:BoundColumn DataField=”ProductN ame” HeaderText=” Product Name” >< /asp:BoundColumn >
< asp:BoundColumn DataField=”UnitPric e” HeaderText=” UnitPrice” > </asp:BoundColumn >
< /Columns >
< /asp:DataGrid >
91. How do you create a permanent cookie?
Permanent cookies are the ones that are most useful. Permanent cookies are available until a specified expiration date, and are stored on the hard disk. The location of cookies differs with each browser, but this doesn’t matter, as this is all handled by your browser and the server. If you want to create a permanent cookie called Name with a value of Nigel, which expires in one month, you’d use the following code Response.Cookies (“Name”) = “Nigel” Response.Cookies (“Name”). Expires = DateAdd (“m”, 1, Now ())
92. What tag do you use to add a hyperlink column to the DataGrid?
< asp:HyperLinkColumn > </ asp:HyperLinkColumn>
93. Which method do you use to redirect the user to another page without performing a round trip to the client?
94. What is the transport protocol you use to call a Web service SOAP ?
95. Explain role based security ?
Role Based Security lets you identify groups of users to allow or deny based on their role in the organization. In Windows NT and Windows XP, roles map to names used to identify user groups. Windows defines several built-in groups, including Administrators, Users, and Guests.To allow or deny access to certain groups of users, add the <ROLES>element to the authorization list in your Web application’ s Web.config file.e.g.
<AUTHORIZATION>< authorization >
< allow roles=”Domain NameAdministrators ” / > < !– Allow Administrators in domain. — >
< deny users=”*” / > < !– Deny anyone else. — >
< /authorization >
97. When do you set “<IDENTITY impersonate= “true” />” ?
Identity is a webconfig declaration under System.web, which helps to control the application Identity of the web applicaton. Which can be at any level(Machine, Site,application ,subdirectory, or page), attribute impersonate with “true” as value specifies that client impersonation is used.
98. What are different templates available in Repeater,DataList and Datagrid ?
Templates enable one to apply complicated formatting to each of the items displayed by a control.Repeater control supports five types of templates.HeaderTem plate controls how the header of the repeater control is formatted.ItemTempl ate controls the formatting of each item displayed.Alternati ngItemTemplate controls how alternate items are formatted and the SeparatorTemplate displays a separator between each item displyed.FooterTemp late is used for controlling how the footer of the repeater control is formatted.The DataList and Datagrid supports two templates in addition to the above five.SelectedItem Template controls how a selected item is formatted and EditItemTemplate controls how an item selected for editing is formatted.
99. What is ViewState ? and how it is managed ?
ASP.NET ViewState is a new kind of state service that developers can use to track UI state on a per-user basis. Internally it uses an an old Web programming trick-roundtripping state in a hidden form field and bakes it right into the page-processing framework.It needs less code to write and maintain state in your Web-based forms.
100. What is web.config file ?
Web.config file is the configuration file for the Asp.net web application. There is one web.config file for one asp.net application which configures the particular application. Web.config file is written in XML with specific tags having specific meanings.It includes databa which includes connections, Session States,Error Handling,Security etc. For example :
< configuration >
< appSettings >
< add key=”ConnectionStri ng”
value=”server= localhost; uid=sa;pwd= ;database= MyDB” / >
< /appSettings >
< /configuration >
101. What is advantage of viewstate and what are benefits?
When a form is submitted in classic ASP, all form values are cleared. Suppose you have submitted a form with a lot of information and the server comes back with an error. You will have to go back to the form and correct the information. You click the back button, and what happens….. ..ALL form values are CLEARED, and you will have to start all over again! The site did not maintain your ViewState.With ASP .NET, the form reappears in the browser window together with all form values.This is because ASP .NET maintains your ViewState. The ViewState indicates the status of the page when submitted to the server.
102. What tags do you need to add within the asp:datagrid tags to bind columns manually?
Set AutoGenerateColumns Property to false on the datagrid tag and then use Column tag and an ASP:databound tag
< asp:DataGrid runat=”server” id=”ManualColumnBin ding” AutoGenerateColumns =”False” >
< Columns >
< asp:BoundColumn HeaderText=” Column1″ DataField=”Column1″ / >
< asp:BoundColumn HeaderText=” Column2″ DataField=”Column2″ / >
< /Columns >
< /asp:DataGrid >
<asp:DataGrid id=ManualColumnBind ing runat=”server” AutoGenerateColumns =”False”>
<COLUMNS> <asp:BoundColumn HeaderText=” Column2″ DataField=”Column2″></asp:BoundColumn>
103. Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box?
DataTextField and DataValueField
104. Which control would you use if you needed to make sure the values in two different controls matched?
CompareValidator is used to ensure that two fields are identical.
105. What is validationsummary server control?where it is used?.
The ValidationSummary control allows you to summarize the error messages from all validation controls on a Web page in a single location. The summary can be displayed as a list, a bulleted list, or a single paragraph, based on the value of the DisplayMode property. The error message displayed in the ValidationSummary control for each validation control on the page is specified by the ErrorMessage property of each validation control. If the ErrorMessage property of the validation control is not set, no error message is displayed in the ValidationSummary control for that validation control. You can also specify a custom title in the heading section of the ValidationSummary control by setting the HeaderText property. You can control whether the ValidationSummary control is displayed or hidden by setting the ShowSummary property. The summary can also be displayed in a message box by setting the ShowMessageBox property to true.
106. What is the sequence of operation takes place when a page is loaded?
BeginTranaction – only if the request is transacted
Init – every time a page is processed
LoadViewState – Only on postback
ProcessPostData1 – Only on postback
Load – every time
ProcessData2 – Only on Postback
RaiseChangedEvent – Only on Postback
RaisePostBackEvent – Only on Postback
PreRender – everytime
BuildTraceTree – only if tracing is enabled
SaveViewState – every time
Render – Everytime
End Transaction – only if the request is transacted
Trace.EndRequest – only when tracing is enabled
UnloadRecursive – Every request
107. Difference between asp and asp.net?.
“ASP (Active Server Pages) and ASP.NET are both server side technologies for building web sites and web applications, ASP.NET is Managed compiled code – asp is interpreted. and ASP.net is fully Object oriented. ASP.NET has been entirely re-architected to provide a highly productive programming experience based on the .NET Framework, and a robust infrastructure for building reliable and scalable web
108. Name the validation control available in asp.net?.
RequiredField, RangeValidator, RegularExpressio n,Custom validator,compare Validator
109. What are the various ways of securing a web site that could prevent from hacking etc .. ?
1) Authentication/ Authorization
2) Encryption/Decrypti on
3) Maintaining web servers outside the corporate firewall. etc.,
110. What is the difference between in-proc and out-of-proc?
An inproc is one which runs in the same process area as that of the client giving tha advantage of speed but the disadvantage of stability becoz if it crashes it takes the client application also with it.Outproc is one which works outside the clients memory thus giving stability to the client, but we have to compromise a bit on speed.
111. When you’re running a component within ASP.NET, what process is it running within on Windows XP? Windows 2000? Windows 2003? On Windows 2003 (IIS 6.0) running in native mode, the component is running within the w3wp.exe process associated with the application pool which has been configured for the web application containing the component.
On Windows 2003 in IIS 5.0 emulation mode, 2000, or XP, it’s running within the IIS helper process whose name I do not remember, it being quite a while since I last used IIS 5.0.
112. What does aspnet_regiis -i do ?
Aspnet_regiis. exe is The ASP.NET IIS Registration tool allows an administrator or installation program to easily update the script maps for anASP.NET application to point to the ASP.NET ISAPI version associated with the tool. The tool can also be used to display the status of all installed versions of ASP. NET, register theASP.NET version coupled with the tool, create client-script directories, and perform other configuration operations.
When multiple versions of the .NET Framework are executing side-by-side on a single computer, the ASP.NET ISAPI version mapped to an ASP.NET application determines which version of the common language runtime is used for the application.
The tool can be launched with a set of optional parameters. Option “i” Installs the version of ASP.NET associated with Aspnet_regiis. exe and updates the script maps at the IIS metabase root and below. Note that only applications that are currently mapped to an earlier version of ASP.NET are affected
113. What is a PostBack?
The process in which a Web page sends data back to the same page on the server.
114. What is ViewState? How is it encoded? Is it encrypted? Who uses ViewState?
ViewState is the mechanism ASP.NET uses to keep track of server control state values that don’t otherwise post back as part of the HTTP form. ViewState Maintains the UI State of a Page
ViewState is base64-encoded. It is not encrypted but it can be encrypted by setting EnableViewStatMAC= “true” & setting the machineKey validation type to 3DES. If you want to NOT maintain the ViewState, include the directive < %@ Page EnableViewState= “false” % > at the top of an .aspx page or add the attribute EnableViewState= “false” to any control.
115. What is the < machinekey > element and what two ASP.NET technologies is it used for?
Configures keys to use for encryption and decryption of forms authentication cookie data and view state data, and for verification of out-of-process session state identification. There fore 2 ASP.Net technique in which it is used are Encryption/Decrypti on & Verification
116. What three Session State providers are available in ASP.NET 1.1? What are the pros and cons of each? ASP.NET provides three distinct ways to store session data for your application: in-process session state, out-of-process session state as a Windows service, and out-of-process session state in a SQL Server database. Each has it advantages.
1.In-process session-state mode
* When using the in-process session-state mode, session-state data is lost if aspnet_wp.exe or the application domain restarts.
* If you enable Web garden mode in the < processModel > element of the application’ s Web.config file, do not use in-process session-state mode. Otherwise, random data loss can occur.
* in-process session state is by far the fastest solution. If you are storing only small amounts of volatile data in session state, it is recommended that you use the in-process provider.
2. The State Server simply stores session state in memory when in out-of-proc mode. In this mode the worker process talks directly to the State Server
3. SQL mode, session states are stored in a SQL Server database and the worker process talks directly to SQL. The ASP.NET worker processes are then able to take advantage of this simple storage service by serializing and saving (using .NET serialization services) all objects within a client’s Session collection at the end of each Web request
Both these out-of-process solutions are useful primarily if you scale your application across multiple processors or multiple computers, or where data cannot be lost if a server or process is restarted.
117. What is the difference between HTTP-Post and HTTP-Get?
As their names imply, both HTTP GET and HTTP POST use HTTP as their underlying protocol. Both of these methods encode request parameters as name/value pairs in the HTTP request.
The GET method creates a query string and appends it to the script’s URL on the server that handles the request.
The POST method creates a name/value pairs that are passed in the body of the HTTP request message.
118. Name and describe some HTTP Status Codes and what they express to the requesting client. When users try to access content on a server that is running Internet Information Services (IIS) through HTTP or File Transfer Protocol (FTP), IIS returns a numeric code that indicates the status of the request. This status code is recorded in the IIS log, and it may also be displayed in the Web browser or FTP client. The status code can indicate whether a particular request is successful or unsuccessful and can also reveal the exact reason why a request is unsuccessful. There are 5 groups ranging from * – * of http status codes exists.
101 – Switching protocols.
200 – OK. The client request has succeeded
302 – Object moved.
400 – Bad request.
50013 – Web server is too busy.
119. Explain < @OutputCache% > and the usage of VaryByParam, VaryByHeader. OutputCache is used to control the caching policies of an ASP.NET page or user control. To cache a page @OutputCache directive should be defined as follows < %@ OutputCache Duration=”100″ VaryByParam= “none” %>
VaryByParam: A semicolon-separated list of strings used to vary the output cache. By default, these strings correspond to a query string value sent with GET method attributes, or a parameter sent using the POST method. When this attribute is set to multiple parameters, the output cache contains a different version of the requested document for each specified parameter. Possible values include none, *, and any valid query string or POST parameter name.
VaryByHeader: A semicolon-separated list of HTTP headers used to vary the output cache. When this attribute is set to multiple headers, the output cache contains a different version of the requested document for each specified header.
120. What is the difference between repeater over datalist and datagrid?
The Repeater class is not derived from the WebControl class, like the DataGrid and DataList. Therefore, the Repeater lacks the stylistic properties common to both the DataGrid and DataList. What this boils down to is that if you want to format the data displayed in the Repeater, you must do so in the HTML markup. The Repeater control provides the maximum amount of flexibility over the HTML produced. Whereas the DataGrid wraps the DataSource contents in an HTML < table >, and the DataList wraps the contents in either an HTML < table > or < span > tags (depending on the DataList’s RepeatLayout property), the Repeater adds absolutely no HTML content other than what you explicitly specify in the templates. While using Repeater control, If we wanted to display the employee names in a bold font we’d have to alter the “ItemTemplate” to include an HTML bold tag, Whereas with the DataGrid or DataList, we could have made the text appear in a bold font by setting the control’s ItemStyle-Font- Bold property to True. The Repeater’s lack of stylistic properties can drastically add to the development time metric. For example, imagine that you decide to use the Repeater to display data that needs to be bold, centered, and displayed in a particular font-face with a particular background color. While all this can be specified using a few HTML tags, these tags will quickly clutter the Repeater’s templates. Such clutter makes it much harder to change the look at a later date. Along with its increased development time, the Repeater also lacks any built-in functionality to assist in supporting paging, editing, or editing of data. Due to this lack of feature-support, the Repeater scores poorly on the usability scale.
However, The Repeater’s performance is slightly better than that of the DataList’s, and is more noticeably better than that of the DataGrid’s. Following figure shows the number of requests per second the Repeater could handle versus the DataGrid and DataList