Asp.Net 2.0 Interview Questions

ASP.NET 2.0 Interview Questions

What is an interface and what is an abstract class?
In an interface, all methods must be abstract (must not be defined). In an abstract class, some methods can be defined. In an interface, no accessibility modifiers are allowed, whereas it is allowed in abstract classes.

Session state vs. View state:
In some cases, using view state is not feasible. The alternative for view state is session state. Session state is employed under the following situations:

Large amounts of data – View state tends to increase the size of both the HTML page sent to the browser and the size of form posted back. Hence session state is used.
Secure data – Though the view state data is encoded and may be encrypted, it is better and secure if no sensitive data is sent to the client. Thus, session state is a more secure option.
Problems in serializing of objects into view state – View state is efficient for a small set of data. Other types like DataSet are slower and can generate a very large view state.
Can two different programming languages be mixed in a single ASPX file?
ASP.NET’s built-in parsers are used to remove code from ASPX files and create temporary files. Each parser understands only one language. Therefore mixing of languages in a single ASPX file is not possible.

Is it possible to see the code that ASP.NET generates from an ASPX file?
By enabling debugging using a directive in the ASPX file or a statement in Web.config, the generated code can be viewed. The code is stored in a CS or VB file (usually in the \%SystemRoot%\Microsoft.NET\Framework\v1.0.nnnn\Temporary ASP.NET Files).

Can a custom .NET data type be used in a Web form?
This can be achieved by placing the DLL containing the custom data type in the application root’s bin directory and ASP.NET will automatically load the DLL when the type is referenced.

List the event handlers that can be included in Global.asax?
Application start and end event handlers
Session start and end event handlers
Per-request event handlers
Non-deterministic event handlers
Can the view state be protected from tampering?
This can be achieved by including an @ Page directive with an EnableViewStateMac=”true” attribute in each ASPX file that has to be protected. Another way is to include the
statement in the Web.config file.

Can the view state be encrypted?
The view state can be encrypted by setting EnableViewStateMac to true and either modifying the element in Machine.config to tag. Then, a byte[] can be declared to read in the data from the input file. This can then be sent to the server.

How do I create an ASPX page that periodically refreshes itself?
The following META tag can be used as a trigger to automatically refresh the page every n seconds:
How do I initialize a TextBox whose TextMode is “password”, with a password?
The TextBox’s Text property cannot be used to assign a value to a password field. Instead, its Value field can be used for that purpose.

ID=”Password” RunAt=”server” />
Why does the control’s PostedFile property always show null when using HtmlInputFile control to upload files to a Web server?
This occurs when an enctype=”multipart/form-data” attribute is missing in the
tag.

How can the focus be set to a specific control when a Web form loads?
This can be achieved by using client-side script:

document.forms[0].TextBox1.focus ()
The above code will set the focus to a TextBox named TextBox1 when the page loads.

How does System.Web.UI.Page’s IsPostBack property work?
IsPostBack checks to see whether the HTTP request is accompanied by postback data containing a __VIEWSTATE or __EVENTTARGET parameter. If there are none, then it is not a postback.

Explain Delegates in c#

Delegates in C# are objects which points towards a function which matches its signature. Delegates are reference type used to encapsulate a method with a specific signature. Delegates are similar to function pointers in C++; however, delegates are type-safe and secure.
Here are some features of delegates:

  • A delegate represents a class.
  • A delegate is type-safe.
  • We can use delegates both for static and instance methods
  • We can combine multiple delegates into a single delegate.
  • Delegates are often used in event-based programming, such as publish/subscribe.
  • We can use delegates in asynchronous-style programming.
  • We can define delegates inside or outside of classes.

Syntax of using delegates

//Declaring delegate
delegate void SampleDelegate(string message);

// declare method with same signature:
static void SampleDelegateMethod(string message) { Console.WriteLine(message); }

// create delegate object
SampleDelegate d1 = SampleDelegateMethod;

// Invoke method with delegate
d1(“my program”);

What is the purpose of connection pooling in ADO.NET?

Connection pooling enables an application to use a connection from a pool of connections that do not need to be re-established for each use. Once a connection has been created and placed in a connection pool, an application can reuse that connection without performing the complete connection creation process.

By default, the connection pool is created when the first connection with a unique connection string connects to the database. The pool is populated with connections up to the minimum pool size. Additional connections can be added until the pool reaches the maximum pool size.

When a user request a connection, it is returned from the pool rather than establishing new connection and, when a user releases a connection, it is returned to the pool rather than being released. But be sure than your connections use the same connection string each time. Here is the Syntax

conn.ConnectionString = “integrated Security=SSPI; SERVER=192.168.0.123; DATABASE=MY_DB; Min Pool Size=4;Max Pool Size=40;Connect Timeout=14;”;

What is the difference between classes and structs in Microsoft.Net?

  • A struct is a value type, while a class is a reference type.
  • When we instantiate a class, memory will be allocated on the heap. When struct gets initiated, it gets memory on the stack.
  • Classes can have explicit parameter less constructors. But structs cannot have this.
  • Classes support inheritance. But there is no inheritance for structs. A struct cannot inherit from another struct or class, and it cannot be the base of a class. Like classes, structures can implement interfaces.
  • We can assign null variable to class. But we cannot assign null to a struct variable, since structs are value type.
  • We can declare a destructor in class but can not in struct.

What is a Strong Name in Microsoft.Net?

In Microsoft.Net a strong name consists of the assembly’s identity. The strong name guarantees the integrity of the assembly. Strong Name includes the name of the .net assembly, version number, culture identity, and a public key token. It is generated from an assembly file using the corresponding private key.
Steps to create strong named assembly:

To create a strong named assembly you need to have a key pair (public key and a private key) file. Use sn -k KeyFile.snk
Open the dot net project to be complied as a strong named assembly. Open AssembyInfo.cs/ AssembyInfo.vb file. Add the following lines to AssemblyInfo file.
[Assembly: AssemblyVersion("1.0.*")]
[assembly: AssemblyDelaySign(false)]
[assembly: AssemblyKeyFile("..\\..\\KeyFile.snk")]
Compile the application, we have created a strong named assembly.

What is the use of XSLT?

XSLT stands for Extensible Stylesheet Language Transformations. This language used in XSL style sheets to transform XML documents into other XML documents.

XSLT is based on template rules which specify how XML documents should be processed. An XSLT processor reads both an XML document and an XSLT style sheet. Based on the instructions the processor finds in the XSLT style sheet, it produce a new XML document. With XSLT we can also produce HTML or XHTML from XML document. With XSLT we can add/remove elements and attributes, rearrange and sort elements, hide and display elements from the output file. Converting XML to HTML for display is probably the most common application of XSLT today.

Explain ACID properties of the database?

All Database systems which include transaction support implement ACID properties to ensure the integrity of the database. ACID stands for Atomicity, Consistency, Isolation and Durability

  • Atomicity: Each transaction is said to be “atomic.” If one part of the transaction fails, the entire transaction fails. Modifications on the data in the database either fail or succeed.
  • Consistency: This property ensures that only valid data will be written to the database. If, for some reason, a transaction is executed that violates the database’s consistency rules, the entire transaction will be rolled back and the database will be restored to a state consistent with those rules.
  • Isolation: It requires that multiple transactions occurring at the same time not impact each other’s execution.
  • Durability: It ensures that any transaction committed to the database will not be lost.

What is the basic functionality of Garbage Collector in Microsft.Net?

The Common Language Runtime (CLR) requires that you create objects in the managed heap, but you do not have to bother with cleaning up the memory once the object goes out of the scope or is no longer needed. The Microsoft .NET Framework Garbage Collector provides memory management capabilities for managed resources. The Garbage Collector frees objects that are not referenced and reclaims their memory. You should set your references to Nothing(null) as soon as you are done with them to ensure your objects are eligible for collection as soon as possible.
Here are the list of some tasks performed by the Garbage collector:

  • Garbage collector reserves a piece of memory as the application starts for the managed heap.
  • Garbage collector controls the managed heap memory currently used and available to an application.
  • Garbage collector allocates memory for new objects within the application.
  • The Garbage Collector attempts to reclaim the memory of objects that are not referenced.

What is a static class?

We can declare a static class. We use static class when there is no data or behavior in the class that depends on object identity. A static class can have only static members. We can not create instances of a static class using the new keyword. .NET Framework common language runtime (CLR) loads Static classes automatically when the program or namespace containing the class is loaded.

Here are some more features of static class

  • Static classes only contain static members.
  • Static classes can not be instantiated. They cannot contain Instance Constructors
  • Static classes are sealed.

What is static member of class?

A static member belongs to the class rather than to the instances of the class. In C# data fields, member functions, properties and events can be declared static. When any instances of the class are created, they cannot be used to access the static member.
To access a static class member, use the name of the class instead of an instance variable
Static methods and Static properties can only access static fields and static events.

Like: int i = Car.GetWheels;
Here Car is class name and GetWheels is static property.

Static members are often used to represent data or calculations that do not change in response to object state.

What is the purpose of Server.MapPath method in Asp.Net?

In Asp.Net Server.MapPath method maps the specified relative or virtual path to the corresponding physical path on the server. Server.MapPath takes a path as a parameter and returns the physical location on the hard drive. Syntax

Suppose your Text files are located at D:\project\MyProject\Files\TextFiles

If the root project directory is MyProject and the aspx file is located at root then to get the same path use code

//Physical path of TextFiles
string TextFilePath=Server.MapPath(“Files/TextFiles”);

What is the use of indexes and what are the types of indexes available in SQL Server?

Indexes are used to find data quickly when a query is processed in any relational database. Indexes improve performance by 10 to 500 times.
Index can improve the performance in following operations:

  • Find the records matching with WHERE clause

    • UPDATE Books SET Availability = 1 WHERE SubjectId =12
    DELETE FROM Books WHERE Price <10
    SELECT * FROM Books WHERE Price BETWEEN 50 AND 80

  • Sorting the result with ORDER BY

    • SELECT * FROM Books ORDER BY Price DESC

  • Grouping records and aggregate values

    • SELECT Count(*) as Units, Price FROM Books GROUP BY Price

There are two types of indexes available in SQL Server: clustered and non-clustered
Clustered index
Clustered index physically reorders the records of a table. Therefore a table can have only one clustered index. Usually a clustered index will be created on the primary key of a table.
Non – Clustered Index
Non – Clustered index are stored in the order of the index key values, but the information in the table is stored in a different order. Means logical sorting of data not Physical. In SQl Server 2005 a table can have 249 non-clustered indexes.
Composite Indexes
A composite index is an index on two or more columns. Both clustered and non-clustered indexes can be composite indexes. If you have composite index on Price and BookName then take can take advantage of it like this:
SELECT BookName, Price FROM Products ORDER BY UnitPrice BookName, Price DESC

What is the difference between abstract class and interface?

We use abstract class and interface where two or more entities do same type of work but in different ways. Means the way of functioning is not clear while defining abstract class or interface. When functionality of each task is not clear then we define interface. If functionality of some task is clear to us but there exist some functions whose functionality differs object by object then we declare abstract class.
We can not make instance of Abstract Class as well as Interface. They only allow other classes to inherit from them. And abstract functions must be overridden by the implemented classes. Here are some differences in abstract class and interface.

  • An interface cannot provide code of any method or property, just the signature. we don’t need to put abstract and public keyword. All the methods and properties defined in Interface are by default public and abstract. An abstract class can provide complete code of methods but there must exist a method or property without body.
  • A class can implement several interfaces but can inherit only one abstract class. Means multiple inheritance is possible in .Net through Interfaces.
  • If we add a new method to an Interface then we have to define implementation for the new method in every implemented class. But If we add a new method to an abstract class then we can provide default implementation and therefore all the existing code might work properly.

What is the use of Master Pages in Asp.Net?

A master page in ASP.Net provides shared HTML, controls, and code that can be used as a template for all of the pages of a website.
Every master page has asp:contentplaceholder control that will be filled by the content of the pages that use this master page.
You can create a master page that has header and footer i.e. a logo, an image, left navigation bar etc and share this content on multiple pages. You need not to put these things on every aspx page.

What is the difference between .Net Remoting and Asp.Net Web Services?

  • ASP.NET Web Services Can be accessed only over HTTP but .Net Remoting Can be accessed over various protocols like TCP, HTTP, SMTP etc.
  • Web Services are based on stateless service architecture but .Net Remoting support for both stateful and stateless environment.
  • Web Services support heterogeneous environments means interoperability across platforms but .Net remoting requires .Net on both server and client end.
  • .NET Remoting provides the fast communication than Web Services when we use the TCP channel and the binary formatter.
  • Web services support only the objects that can be serialized but .NET Remoting can provide support to all objects that inherit MarshalByRefObject.
  • Web Services are reliable than .Net remoting because Web services are always hosted in IIS.
  • Web Services are ease to create and deploy but .Net remoting is bit complex to program.

What would be the common layers in an n- tier architecture based web application?

Common layers in an n- tier architecture

  • Presentation GUI: Look & Feel ,Html, aspx file, JavaScript, window forms etc.
  • Controller- Work flow layer: aspx.cs file, means event handlers and Data binding with controls etc.
  • Business Logic: where we implement business rules like add book, search library etc.
  • Data Access: SQLHelper.cs like create connection, get DataSet, Execute Query etc.
  • Physical Data: tables, views, stored procedures, indexes etc.

What are the different state management techniques used in asp.net for web applications?

In ASP.Net the state can be maintained in following ways

Server-side state management
Application objects
Session Variables
Database
Client-side state management
Cookies
Hidden input fields
Query String
ViewState

How to get records in random order from a sql query in sql server?

In SQL Server we can get records in random order from a sql query using NEWID() Function like:

SELECT Subject FROM dbo.forumThreads ORDER BY NEWID()

What is WSDL?
WSDL is an XML format for describing network services as a set of endpoints operating on messages containing either document-oriented or procedure-oriented information. The operations and messages are described abstractly, and then bound to a concrete network protocol and message format to define an endpoint. Related concrete endpoints are combined into abstract endpoints (services). (Source: www.w3.org)

What is UDDI?
UDDI stands for Universal Description, Discovery, and Integration. It is like an “Yellow Pages” for Web Services. It is maintained by Microsoft, IBM, and Ariba, and is designed to provide detailed information regarding registered Web Services for all vendors. The UDDI can be queried for specific Web Services.

Is it possible to generate the source code for an ASP.NET Web service from a WSDL?
The Wsdl.exe tool (.NET Framework SDK) can be used to generate source code for an ASP.NET web service with its WSDL link.

Example: wsdl /server http://api.google.com/GoogleSearch.wsdl.

Why do uploads fail while using an ASP.NET file upload control to upload large files?
ASP.NET limits the size of file uploads for security purposes. The default size is 4 MB. This can be changed by modifying the maxRequestLength attribute of Machine.config’s element.

Describe the difference between inline and code behind.
Inline code is written along side the HTML in a page. Code-behind is code written in a separate file and referenced by the .aspx page.

——————————————————————————————-
1. What is the name of the property of ASP.NET page that you can query to determine that a ASP.NET page is being requested not data being submitted to web server?
A. FirstGet
B. Initialized
C. IncludesData
D. IsPostBack

IsPostBack

2. While creating a Web site with the help of Visual Studio 2005 on a remote computer that does not have Front Page Server Extensions installed, which Web site type will you create in Visual Studio 2005?
A. Remote HTTP
B. File
C. FTP
D. Local HTTP

Hypertext Transfer Protocol (HTTP)

3. If you want to create a new Web site with the help of Visual Studio 2005 on a Web server that is hosted by your ISP (Internet Services provider) and the Web server has Front Page Server Extensions installed, what type of Web site type would you create in Visual Studio 2005?
A. Local HTTP
B. File
C. FTP
D. Remote HTTP

Hypertext Transfer Protocol (HTTP)

4. For separating server-side code from client-side code on a ASP.NET page, what programming model should you use?
A. Separation model
B. Code-Behind model
C. In-Line model
D. ClientServer model

5. Amit created a new Web site using Visual Studio 2005 in programming language C#. Later, Amit received an existing Web page from his boss, which consisted of the Contact.aspx file with the Contact.aspx.vb code-behind page. What must Amit do to use these files?
A. Amit can simply add the files Contact.aspx, Contact.aspx.vb into the existing Web site, because ASP.NET 2.0 supports Web sites that have Web pages that were programmed with different languages.
B. The Contact.aspx file will work, but Amit must rewrite the code-behind page using C#.
C. Both files Contact.aspx and Contact.aspx.vb must be rewritten in C#.
D. Amit must create a new Web site that contains these files Contact.aspx and Contact.aspx.vb. Set a Web reference to the new site.

6. If you want to make a configuration setting change in your server that will affect to all Web and Windows applications on the current machine. Where you will make the changes?
A. Global.asax
B. Web.config
C. Machine.config
D. Global.asax

7. If you want to make a configuration setting change that will affect only the current Web application. Which file will you change?
A. Web.config that is in the same folder as the Machine.config file
B. Web.config in the root of the Web application
C. Machine.config
D. Global.asax

8. For making a configuration setting change that will affect only the current Web application. Is there any tool that has a user-friendly Graphical User Interface (GUI)?
A. The Microsoft Management Utility
B. Microsoft Word
C. Visual Studio, using the Tools > Options path
D. Web Site Administration Tool

9. How will you identify which event in the ASP.NET Web page life cycle takes the longest time to execute?
A. Turn on ASP.NET trace and run the Web application.
B. Add a few code to each of the page life-cycle events that will print the current time.
C. In the Web.config file, add the monitorTimings attribute and set it to True.
D. In the Web site properties, turn on the performance monitor and run the Web application. After that, open performance monitor to see the timings.

11. You are interested in examining the data that is posted to the Web server. What trace result section can you use to see this information?
A. Control Tree
B. Headers Collection
C. Form Collection
D. Server Variables

12. While creating web site you need to add an HTML Web server control to the Web page, you need to drag an HTML element from the ToolBox of Visual Studio 2005 to the Web page and then which of the following tasks you will perform?
A. Right-click the HTML element and click Run=Server.
B. Double-click the HTML element to convert it to an HTML server control.
C. Right-click the HTML element and click Run As Server Control.
D. Click the HTML element and set ServerControl to true in the Properties window.

13. While testing your ASP.NET web application you noticed that while clicking on CheckBox of one of the web page it does not cause a PostBack; you required that the CheckBox should make PostBack so Web page can be update on the server-side code. How can you make the CheckBox to cause a PostBack?
A. Set the AutoPostBack property to true.
B. Add JavaScript code to call the ForcePostBack method.
C. Set the PostBackAll property of the Web page to true.
D. Add server-side code to listen for the click event from the client.

14. While writing code in Visual Studio 2005 you creates a new instance of a ASP.NET TextBox server control, what do you need to do to get the TextBox to display on the Web page?
A. Call the ShowControl method on the TextBox.
B. Set the VisibleControl to true on the TextBox.
C. Add the TextBox instance to the form1.Controls collection.
D. Execute the AddControl method on the Web page.

15. While creating your ASP.NET web based application you want to create multiple RadioButton server controls which should be mutually exclusive, what property of RadioButton server controls you must set?
A. Exclusive
B. MutuallyExclusive
C. Grouped
D. GroupName

16. While creating an ASP.NET web application with the help of Visual Studio 2005 you are creates a Web page that has several related buttons, such as fast-forward, reverse, play, stop, and pause. There should be one event handler that handles the processes of PostBack from these Button server controls. Other than the normal Submit button, what type of button can you create?
A. OneToMany
B. Command
C. Reset
D. ManyToOne

17. In the Design view in Visual Studio 2005 of an ASP.NET web page, what is the easiest way to create an event handler for the default event of a ASP.NET server control?
A. Open the code-behind page and write the code.
B. Right-click the control and select Create Handler.
C. Drag an event handler from the ToolBox to the desired control.
D. Double-click the control.

18. Which of the following represents the best use of the Table, TableRow, and Table-Cell controls?
A. To create and populate a Table in Design view
B. To create a customized control that needs to display data in a tabular fashion
C. To create and populate a Table with images
D. To display a tabular result set

19. For your ASP.NET web application your graphics designer created elaborate images that show the product lines of your company. Some of graphics of the product line are rectangular, circular, and others are having complex shapes. You need to use these images as a menu on your Web site. What is the best way of incorporating these images into your Web site?
A. Use ImageButton and use the x- and y-coordinates that are returned when the user clicks to figure out what product line the user clicked.
B. Use the Table, TableRow, and TableCell controls, break the image into pieces that are displayed in the cells, and use the TableCell control’s Click event to identify the product line that was clicked.
C. Use the MultiView control and break up the image into pieces that can be displayed in each View control for each product line. Use the Click event of the View to identify the product line that was clicked.
D. Use an ImageMap control and define hot spot areas for each of the product lines. Use the PostBackValue to identify the product line that was clicked.

20. You are writing ASP.NET 2.0 Web site that collects lots of data from users, and the data collection forms spreads over multiple ASP.NET Web pages. When the user reaches the last page, you need to gather all of data, validate the data, and save the data to the SQL Server database. You have noticed that it can be rather difficult to gather the data that is spread over multiple pages and you want to simplify this application. What is the easiest control to implement that can be used to collect the data on a single Web page?
A. The View control
B. The TextBox control
C. The Wizard control
D. The DataCollection control

21. In your ASP.NET 2.0 web application you want to display an image that is selected from a collection of images. What approach will you use to implementing this?
A. Use the ImageMap control and randomly select a HotSpot to show or hide.
B. Use the Image control to hold the image and a Calendar control to randomly select a date for each image to be displayed.
C. Use the AdServer control and create an XML file with configuration of the control.
D. Use an ImageButton control to predict randomness of the image to be loaded based on the clicks of the control.

22. In your ASP.NET web application you want to display a list of clients on a Web page. The client list displays 10 clients at a time, and you require the ability to edit the clients. Which Web control is the best choice for this scenario?
A. The DetailsView control
B. The Table control
C. The GridView control
D. The FormView control

23. While developing ASP.NET 2.0 web application you want to display a list of parts in a master/detail scenario where the user can select a part number using a list that takes a minimum amount of space on the Web page. When the part is selected, a DetailsView control displays all the information about the part and allows the user to edit the part. Which Web control is the best choice to display the part number list for this scenario?
A. The DropDownList control
B. The RadioButtonList control
C. The FormView control
D. The TextBox control

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

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