A cookie is a small bit of text that accompanies requests and pages as they go between the Web server and browser. The cookie contains information the Web application can read whenever the user visits the site.
For example, if a user requests a page from your site and your application sends not just a page, but also a cookie containing the date and time, when the user's browser gets the page, the browser also gets the cookie, which it stores in a folder on the user's hard disk.
Later, if user requests a page from your site again, when the user enters the URL the browser looks on the local hard disk for a cookie associated with the URL. If the cookie exists, the browser sends the cookie to your site along with the page request. Your application can then determine the date and time that the user last visited the site. You might use the information to display a message to the user or check an expiration date.
Cookies are associated with a Web site, not with a specific page, so the browser and server will exchange cookie information no matter what page the user requests from your site. As the user visits different sites, each site might send a cookie to the user's browser as well; the browser stores all the cookies separately.
Cookies help Web sites store information about visitors. More generally, cookies are one way of maintaining continuity in a Web application—that is, of performing state management. Except for the brief time when they are actually exchanging information, the browser and Web server are disconnected. Each request a user makes to a Web server is treated independently of any other request. Many times, however, it's useful for the Web server to recognize users when they request a page. For example, the Web server on a shopping site keeps track of individual shoppers so the site can manage shopping carts and other user-specific information. A cookie therefore acts as a kind of calling card, presenting pertinent identification that helps an application know how to proceed.
Cookies are used for many purposes, all relating to helping the Web site remember users. For example, a site conducting a poll might use a cookie simply as a Boolean value to indicate whether a user's browser has already participated in voting so that the user cannot vote twice. A site that asks a user to log on might use a cookie to record that the user already logged on so that the user does not have to keep entering credentials.
Cookie Limitations
Most browsers support cookies of up to 4096 bytes. Because of this small limit, cookies are best used to store small amounts of data, or better yet, an identifier such as a user ID. The user ID can then be used to identify the user and read user information from a database or other data store. (See the section "Cookies and Security" below for information about security implications of storing user information.)
Browsers also impose limitations on how many cookies your site can store on the user's computer. Most browsers allow only 20 cookies per site; if you try to store more, the oldest cookies are discarded. Some browsers also put an absolute limit, usually 300, on the number of cookies they will accept from all sites combined.
A cookie limitation that you might encounter is that users can set their browser to refuse cookies. If you define a P3P privacy policy and place it in the root of your Web site, more browsers will accept cookies from your site. However, you might have to avoid cookies altogether and use a different mechanism to store user-specific information. A common method for storing user information is session state, but session state depends on cookies, as explained later in the section "Cookies and Session State."
The ASP.NET AJAX Interview Questions contains the most frequently asked questions in ASP.NET AJAX. These lists of questions will gauge your familiarity with the ASP.NET AJAX platform.
What is Ajax?
The term Ajax was coined by Jesse James Garrett and is a short form for "Asynchronous Javascript and XML". Ajax represents a set of commonly used techniques, like HTML/XHTML, CSS, Document Object Model(DOM), XML/XSLT, Javascript and the XMLHttpRequest object, to create RIA's (Rich Internet Applications).
Ajax gives the user, the ability to dynamically and asynchronously interact with a web server, without using a plug-in or without compromising on the user’s ability to interact with the page. This is possible due to an object found in browsers called the XMLHttpRequest object.
What is ASP.NET AJAX?
‘ASP.NET AJAX’ is a terminology coined by Microsoft for ‘their’ implementation of AJAX, which is a set of extensions to ASP.NET. These components allow you to build rich AJAX enabled web applications, which consists of both server side and client side libraries.
Which is the current version of ASP.NET AJAX Control Toolkit?
As of this writing, the toolkit version is Version 1.0.20229 (if you are targeting Framework 2.0, ASP.NET AJAX 1.0 and Visual Studio 2005) and Version 3.0.20229 (if targeting .NET Framework 3.5 and Visual Studio 2008).
What role does the ScriptManager play?
The ScriptManager manages all ASP.NET AJAX resources on a page and renders the links for the ASP.NET AJAX client libraries, which lets you use AJAX functionality like PageMethods, UpdatePanels etc. It creates the PageRequestManager and Application objects, which are prominent in raising events during the client life cycle of an ASP.NET AJAX Web page. It also helps you create proxies to call web services asynchronously.
Can we use multiple ScriptManager on a page?
No. You can use only one ScriptManager on a page.
What is the role of a ScriptManagerProxy?
A page can contain only one ScriptManager control. If you have a Master-Content page scenario in your application and the MasterPage contains a ScriptManager control, then you can use the ScriptManagerProxy control to add scripts to content pages.
Also, if you come across a scenario where only a few pages in your application need to register to a script or a web service, then its best to remove them from the ScriptManager control and add them to individual pages, by using the ScriptManagerProxy control. That is because if you added the scripts using the ScriptManager on the Master Page, then these items will be downloaded on each page that derives from the MasterPage, even if they are not needed, which would lead to a waste of resources.
What are the requirements to run ASP.NET AJAX applications on a server?
You would need to install ‘ASP.NET AJAX Extensions’ on your server. If you are using the ASP.NET AJAX Control toolkit, then you would also need to add the AjaxControlToolkit.dll in the /Bin folder.
Note: ASP.NET AJAX 1.0 was available as a separate downloadable add-on for ASP.NET 2.0. With ASP.NET 3.5, the AJAX components have been integrated into ASP.NET.
Explain the UpdatePanel?
The UpdatePanel enables you to add AJAX functionality to existing ASP.NET applications. It can be used to update content in a page by using Partial-page rendering. By using Partial-page rendering, you can refresh only a selected part of the page instead of refreshing the whole page with a postback.
Can I use ASP.NET AJAX with any other technology apart from ASP.NET?
To answer this question, check out this example of using ASP.NET AJAX with PHP, to demonstrate running ASP.NET AJAX outside of ASP.NET. Client-Side ASP.NET AJAX framework can be used with PHP and Coldfusion.
How can you cancel an Asynchronous postback?
Yes you can. Read my article over here.
Difference between Server-Side AJAX framework and Client-side AJAX framework?
ASP.NET AJAX contains both a server-side Ajax framework and a client-side Ajax framework. The server-side framework provides developers with an easy way to implement Ajax functionality, without having to possess much knowledge of JavaScript. The framework includes server controls and components and the drag and drop functionality. This framework is usually preferred when you need to quickly ajaxify an asp.net application. The disadvantage is that you still need a round trip to the server to perform a client-side action.
The Client-Side Framework allows you to build web applications with rich user-interactivity as that of a desktop application. It contains a set of JavaScript libraries, which is independent from ASP.NET. The library is getting rich in functionality with every new build released.
How can you debug ASP.NET AJAX applications?
Explain about two tools useful for debugging: Fiddler for IE and Firebug for Mozilla.
Can we call Server-Side code (C# or VB.NET code) from javascript?
Yes. You can do so using PageMethods in ASP.NET AJAX or using webservices.
Can you nest UpdatePanel within each other?
Yes, you can do that. You would want to nest update panels to basically have more control over the Page Refresh.
How can you to add JavaScript to a page when performing an asynchronous postback?
Use the ScriptManager class. This class contains several methods like the RegisterStartupScript(), RegisterClientScriptBlock(), RegisterClientScriptInclude(), RegisterArrayDeclaration(),RegisterClientScriptResource(), RegisterExpandoAttribute(), RegisterOnSubmitStatement() which helps to add javascript while performing an asynchronous postback.
Explain differences between the page execution lifecycle of an ASP.NET page and an ASP.NET AJAX page?
In an asynchronous model, all the server side events occur, as they do in a synchronous model. The Microsoft AJAX Library also raises client side events. However when the page is rendered, asynchronous postback renders only the contents of the update panel, where as in a synchronous postback, the entire page is recreated and sent back to the browser.
Explain the AJAX Client life-cycle events
Here’s a good article about the same.
Is the ASP.NET AJAX Control Toolkit(AjaxControlToolkit.dll) installed in the Global Assembly Cache?
No. You must copy the AjaxControlToolkit.dll assembly to the /Bin folder in your application.
Those were some frequently asked questions you should have knowledge about. In one of the coming articles, we will cover some more ASP.NET AJAX FAQ’s which were not covered in this article. I hope this article was useful and I thank you for viewing it.
First things first. Do they even know what MVC. Not just the TAL but can they describe it to you. Then what are the benefits. Also it doesn't hurt to ask them their opinion on it. It is good to know if they even like MVC frameworks.
Next, ask them if they have used any other MVC frameworks. Struts, Spring MVC, Zend or anything like that.
Ask them if they know when a session starts, the general state problem on the net etc etc.
Also a little bit of database. Ask them if they have any experience with database persistence layers.
Then just because you can ask a hard technical question, ask them to write a function that compares two binary trees both in value and structure to see if they are identicial.
There are two main ways of multi-threading which .NET encourages:
To start your own threads with ThreadStart delegates, you should create a new thread "manually" for long-running tasks.
Using the ThreadPool class either directly (using ThreadPool.QueueUserWorkItem) or indirectly using asynchronous methods (such as Stream.BeginRead, or calling BeginInvoke on any delegate).
Use the thread pool only for brief jobs.
Benefits of using the Thread Pool.
Benefits of using the Thread Pool.
The benefits of using a Thread Pool are:
Thread creation and destruction overhead is negated,
Better performance and better system stability.
It is better to use a thread pool in cases where the number of threads is very large.
What is Master Page in ASP.NET?
A Master page offers a template for one or more web forms. It defines placeholders for the content, which can be overridden by the content pages. The content pages contains only content. When users request the content page, ASP.NET merges the layout of the master page with the content of the content page and produce output.
Advantages of using Master Page in ASP.NET
Master pages enables consistent and standardized layout to the website.
You can make layout changes of the site in the master page instead of making change in the pages.
It is very easy to implement.
Advantages and disadvantages of using multithreading
Advantages:
Simultaneous access to multiple applications
Reduced number of required servers
Improved performance and concurrency
Simplified coding of remote procedure calls and conversations
Disadvantages:
Code writing, debugging, managing concurrency, testing, porting existing code is difficult in multithreading and multicontexting.
Programmers need to remove static variables and replace any code that is not thread-safe to introduce threading into a previously non threaded application.
ADO.NET is a part of the Microsoft .NET Framework. This framework provides the set of classes that deal with data communication between various layers of the software architecture and the database. It provides a continious access to different data source types such as SQL Server versions 7, 2000, 2005. It also provides connectivity options to data sources through OLE DB and XML. Connectivity may be established with other databases like Oracle, MySQL etc. as well.
ADO.NET has the ability to separate data access
mechanisms, data manipulation mechanisms and data connectivity mechanisms.
ADO.NET introduces along with it the disconnected architecture. In a disconncted architecture, data may be stored in a DataSet. It contains providers for connecting to databases, commands for execution and retrieval of results.
The classes for ADO.NET are stored in the DLL System.Data.dll.
The OPTIONS method represents a request for information about the communication options available on the request/response chain identified by the Request-URI. This method allows the client to determine the options and/or requirements associated with a resource, or the capabilities of a server, without implying a resource action or initiating a resource retrieval.
Responses to this method are not cacheable.
If the OPTIONS request includes an entity-body (as indicated by the presence of Content-Length or Transfer-Encoding), then the media type MUST be indicated by a Content-Type field. Although this specification does not define any use for such a body, future extensions to HTTP might use the OPTIONS body to make more detailed queries on the server. A server that does not support such an extension MAY discard the request body.
If the Request-URI is an asterisk ("*"), the OPTIONS request is intended to apply to the server in general rather than to a specific resource. Since a server's communication options typically depend on the resource, the "*" request is only useful as a "ping" or "no-op" type of method; it does nothing beyond allowing the client to test the capabilities of the server. For example, this can be used to test a proxy for HTTP/1.1 compliance (or lack thereof).
If the Request-URI is not an asterisk, the OPTIONS request applies only to the options that are available when communicating with that resource.
A 200 response SHOULD include any header fields that indicate optional features implemented by the server and applicable to that resource (e.g., Allow), possibly including extensions not defined by this specification. The response body, if any, SHOULD also include information about the communication options. The format for such a
body is not defined by this specification, but might be defined by future extensions to HTTP. Content negotiation MAY be used to select the appropriate response format. If no response body is included, the response MUST include a Content-Length field with a field-value of "0".
The Max-Forwards request-header field MAY be used to target a specific proxy in the request chain. When a proxy receives an OPTIONS request on an absoluteURI for which request forwarding is permitted, the proxy MUST check for a Max-Forwards field. If the Max-Forwards field-value is zero ("0"), the proxy MUST NOT forward the message; instead, the proxy SHOULD respond with its own communication options. If the Max-Forwards field-value is an integer greater than zero, the proxy MUST decrement the field-value when it forwards the request. If no Max-Forwards field is present in the request, then the forwarded request MUST NOT include a Max-Forwards field.
24. While developing ASP.NET 2.0 web application you have a DataSet containing a Customer DataTable and an Order DataTable. You want to easily navigate from an Order DataRow to the Customer who placed the order. What object will allow you to easily navigate from the Order to the Customer?
A. The DataColumn object
B. The DataTable object
C. The DataRow object
D. The DataRelation object
25. Which of the following is a requirement when merging modified data into a DataSet?
A. A primary key must be defined on the DataTable objects.
B. The DataSet schemas must match in order to merge.
C. The destination DataSet must be empty prior to merging.
D. A DataSet must be merged into the same DataSet that created it.
26. You are working with a DataSet and want to be able to display data, sorted different ways. How do you do so?
A. Use the Sort method on the DataTable object.
B. Use the DataSet object’s Sort method.
C. Use a DataView object for each sort.
D. Create a DataTable for each sort, using the DataTable object’s Copy method, and then Sort the result.
27. Which of the following ways can you proactively clean up a database connection’s resources?
A. Execute the DbConnection object’s Cleanup method.
B. Execute the DbConnection object’s Close method.
C. Assign Nothing (C# null) to the variable that references the DbConnection object.
D. Create a using block for the DbConnection object.
29. What event can you subscribe to if you want to display information from SQL Print statements?
A. InfoMessage
B. MessageReceived
C. PostedMessage
D. NewInfo
30. To perform asynchronous data access, what must be added to the connection string?
A. BeginExecute=true
B. MultiThreaded=true
C. MultipleActiveResultSets=true
D. Asynchronous=true
31. Which class can be used to create an XML document from scratch?
A. XmlConvert
B. XmlDocument
C. XmlNew
D. XmlSettings
32. Which class can be used to perform data type conversion between .NET data types and XML types?
A. XmlType
B. XmlCast
C. XmlConvert
D. XmlSettings
24. While developing ASP.NET 2.0 web application you have a DataSet containing a Customer DataTable and an Order DataTable. You want to easily navigate from an Order DataRow to the Customer who placed the order. What object will allow you to easily navigate from the Order to the Customer? A. The DataColumn object B. The DataTable object C. The DataRow object D. The DataRelation object
25. Which of the following is a requirement when merging modified data into a DataSet? A. A primary key must be defined on the DataTable objects. B. The DataSet schemas must match in order to merge. C. The destination DataSet must be empty prior to merging. D. A DataSet must be merged into the same DataSet that created it.
26. You are working with a DataSet and want to be able to display data, sorted different ways. How do you do so? A. Use the Sort method on the DataTable object. B. Use the DataSet object’s Sort method. C. Use a DataView object for each sort. D. Create a DataTable for each sort, using the DataTable object’s Copy method, and then Sort the result.
27. Which of the following ways can you proactively clean up a database connection’s resources? A. Execute the DbConnection object’s Cleanup method. B. Execute the DbConnection object’s Close method. C. Assign Nothing (C# null) to the variable that references the DbConnection object. D. Create a using block for the DbConnection object.
29. What event can you subscribe to if you want to display information from SQL Print statements? A. InfoMessage B. MessageReceived C. PostedMessage D. NewInfo
30. To perform asynchronous data access, what must be added to the connection string? A. BeginExecute=true B. MultiThreaded=true C. MultipleActiveResultSets=trueD. Asynchronous=true
31. Which class can be used to create an XML document from scratch? A. XmlConvert B. XmlDocument C. XmlNew D. XmlSettings
32. Which class can be used to perform data type conversion between .NET data types and XML types? A. XmlType B. XmlCast C. XmlConvert D. XmlSettings
