asp.net questions

1. What do I need to create and run an ASP.NET application?

• Windows 2000, Windows Server 2003 or Windows XP.
• ASP.NET, which can be either the redistributable (included in the .NET SDK) or Visual Studio .NET.

1. Where can I download the .NET SDK?

   .NET SDK can be obtained here.

   (You have to install the Microsoft .NET Framework Version 1.1 Redistributable Package before installing the .NET SDK.)

2. Are there any free IDEs for the .NET SDK?
   • Microsoft provides Visual Studio 2005 Express Edition Beta for free. Of particular interest to the ASP.NET developers would be the Visual Web Developer 2005 Express Edition Beta 2 available as a free download.
   • The ASP.NET Web Matrix Project (supported by Microsoft) is a free IDE for developing ASP.NET applications and is available here.
   • There is also a free open-source UNIX version of the Microsoft .NET development platform called Mono available for download here.
   • Another increasingly popular Open Source Development Environment for .NET is the #develop (short for SharpDevelop) available for download here.
3. When was ASP.NET released?

   ASP.NET is a part of the .NET framework which was released as a software platform in 2002.

4. Is a new version coming up?

   ASP.NET 2.0, Visual Studio 2005 (Whidbey), Visual Web Developer 2005 Express Edition are the next releases of Microsoft's Web platform and tools. They have already been released as Beta versions. They are scheduled to be released in the week of November 7, 2005.

5. Explain Namespace.

   Namespaces are logical groupings of names used within a program. There may be multiple namespaces in a single application code, grouped based on the identifiers’ use. The name of any given identifier must appear only once in its namespace.

6. List the types of Authentication supported by ASP.NET.
   • Windows (default)
   • Forms
   • Passport
   • None (Security disabled)
7. What is CLR?

   Common Language Runtime (CLR) is a run-time environment that manages the execution of .NET code and provides services like memory management, debugging, security, etc. The CLR is also known as Virtual Execution System (VES).

8. What is CLI?

   The CLI is a set of specifications for a runtime environment, including a common type system, base class library, and a machine-independent intermediate code known as the Common Intermediate Language (CIL). (Source: Wikipedia.)

9. List the various stages of Page-Load lifecycle.
   • Init()
   • Load()
   • PreRender()
   • Unload()
10. Explain Assembly and Manifest.

    An assembly is a collection of one or more files and one of them (DLL or EXE) contains a special metadata called Assembly Manifest. The manifest is stored as binary data and contains details like versioning requirements for the assembly, the author, security permissions, and list of files forming the assembly. An assembly is created whenever a DLL is built. The manifest can be viewed programmatically by making use of classes from the System.Reflection namespace. The tool Intermediate Language Disassembler (ILDASM) can be used for this purpose. It can be launched from the command prompt or via Start> Run.

11. What is Shadow Copy?

    In order to replace a COM component on a live web server, it was necessary to stop the entire website, copy the new files and then restart the website. This is not feasible for the web servers that need to be always running. .NET components are different. They can be overwritten at any time using a mechanism called Shadow Copy. It prevents the Portable Executable (PE) files like DLLs and EXEs from being locked. Whenever new versions of the PEs are released, they are automatically detected by the CLR and the changed components will be automatically loaded. They will be used to process all new requests not currently executing, while the older version still runs the currently executing requests. By bleeding out the older version, the update is completed.

12. What is DLL Hell?

    DLL hell is the problem that occurs when an installation of a newer application might break or hinder other applications as newer DLLs are copied into the system and the older applications do not support or are not compatible with them. .NET overcomes this problem by supporting multiple versions of an assembly at any given time. This is also called side-by-side component versioning.

13. Explain Web Services.

    Web services are programmable business logic components that provide access to functionality through the Internet. Standard protocols like HTTP can be used to access them. Web services are based on the Simple Object Access Protocol (SOAP), which is an application of XML. Web services are given the .asmx extension.

14. Explain Windows Forms.

    Windows Forms is employed for developing Windows GUI applications. It is a class library that gives developers access to Windows Common Controls with rich functionality. It is a common GUI library for all the languages supported by the .NET Framework.

15. What is Postback?

    When an action occurs (like button click), the page containing all the controls within the tag performs an HTTP POST, while having itself as the target URL. This is called Postback.

16. Explain the differences between server-side and client-side code?

    Server side scripting means that all the script will be executed by the server and interpreted as needed. Client side scripting means that the script will be executed immediately in the browser such as form field validation, clock, email validation, etc. Client side scripting is usually done in VBScript or JavaScript. Since the code is included in the HTML page, anyone can see the code by viewing the page source. It also poses as a possible security hazard for the client computer.

17. Enumerate the types of Directives.
    • @ Page directive
    • @ Import directive
    • @ Implements directive
    • @ Register directive
    • @ Assembly directive
    • @ OutputCache directive
    • @ Reference directive
18. What is Code-Behind?

    Code-Behind is a concept where the contents of a page are in one file and the server-side code is in another. This allows different people to work on the same page at the same time and also allows either part of the page to be easily redesigned, with no changes required in the other. An Inherits attribute is added to the @ Page directive to specify the location of the Code-Behind file to the ASP.NET page.

19. Describe the difference between inline and code behind.

    Inline code is written along side the HTML in a page. There is no separate distinction between design code and logic code. Code-behind is code written in a separate file and referenced by the .aspx page.

20. List the ASP.NET validation controls?
    • RequiredFieldValidator
    • RangeValidator
    • CompareValidator
    • RegularExpressionValidator
    • CustomValidator
    • ValidationSummary
21. What is Data Binding?

    Data binding is a way used to connect values from a collection of data (e.g. DataSet) to the controls on a web form. The values from the dataset are automatically displayed in the controls without having to write separate code to display them.

22. Describe Paging in ASP.NET.

    The DataGrid control in ASP.NET enables easy paging of the data. The AllowPaging property of the DataGrid can be set to True to perform paging. ASP.NET automatically performs paging and provides the hyperlinks to the other pages in different styles, based on the property that has been set for PagerStyle.Mode.

23. Should user input data validation occur server-side or client-side? Why?

    All user input data validation should occur on the server and minimally on the client-side, though it is a good way to reduce server load and network traffic because we can ensure that only data of the appropriate type is submitted from the form. It is totally insecure. The user can view the code used for validation and create a workaround for it. Secondly, the URL of the page that handles the data is freely visible in the original form page. This will allow unscrupulous users to send data from their own forms to your application. Client-side validation can sometimes be performed where deemed appropriate and feasible to provide a richer, more responsive experience for the user.

24. What is the difference between Server.Transfer and Response.Redirect?
    • Response.Redirect: This tells the browser that the requested page can be found at a new location. The browser then initiates another request to the new page loading its contents in the browser. This results in two requests by the browser.
    • Server.Transfer: It transfers execution from the first page to the second page on the server. As far as the browser client is concerned, it made one request and the initial page is the one responding with content. The benefit of this approach is one less round trip to the server from the client browser. Also, any posted form variables and query string parameters are available to the second page as well.

Web Services

Asp Net Web Services: Here are some web services interview questions which is very helpful in interviews. This great listing of interview questions provides a lot of information on Web Services Questions and Web Services Faqs. Not at all, instead of web services faqs and interview questions you can also learn how to use web services in asp net. If you need more web services faqs used in asp net you can also contact us for more info।

Question: Can you define basic element of WebServices and explain any one from them?
Answer: These are as follows SOAP, WSDL and UDDI. And I am explaining about the SOAP(Simple Object Access Protocol) it is a communication protocol it is for communication between application it is platform and language independent.It is based on XML and also help to get from Firwall.

Question: Explain functioning of Web Services Protocols ?
Answer: Http-Get:- This is standard protocol that helps client to communicate with server with HTTP.When client send a request to server via HTTP request and reuired parameter are attached with the querystring.Example:-
http://www.dotnetquestion.info/dotnet/interview.aspx?id=pervej&cast=munjal and we get the value from querystring.
Request.querystring("id")
Request.querystring("cast").

Http-Post:-This is same as Http-Get but the diffrence is that in place of sending parameters onto the URL information is send with HTTP request message with some extra information which contains Parameters and their values.This Protocols is limited to sending name/value pairs.

SOAP:-The only diffrence is that its relies on the XML as compares to Http-Get,Http-Post.SOAP can send not only the name/value pairs but also some complex object also as for example datatypes,class,objects.SOAP can also uses request/reponse model as Http-Get,Http-post but it is not limited to Request/Response it can also send types of message.Because its uses XML that is pure text so firewalls not created so much problem because its easily converted in to HTML. .

Question: Why do some web service classes derive from System.Web.WebServices while others do not ?
Answer: Those asp net Web Service classes which employ objects like Application, Session, Context, Server, and User have to derive from System।Web.WebServices. If it does not use these objects, it is not necessary to be derived from it.

Question: What is WSDL ?
Answer: 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).

Question: What is the standard you use to wrap up a call to a Web service ?
Answer: HTTP with SOAP.

Question: What is Asp Net Web Services ?
Answer: Web services are programmable business logic components that provide access to functionality through the Internet. Standard protocols like HTTP can be used to access them. Web services are based on the Simple Object Access Protocol (SOAP), which is an application of XML. Web services are given the .asmx extension..

Question: Define Protocols that helps Web Services in Asp Net?
Answer: From my point of view Web Services used three protocols for interacting with the clients.Http-Post,Http-Get,SOAP.

Question: What are VSDISCO files ?
Answer: VSDISCO files are DISCO files that enable dynamic discovery of Web Services. ASP.NET links the VSDISCO to a 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.

Question: What is UDDI ?
Answer: 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.

Question: Is it possible to generate the source code for an ASP.NET Web service from a WSDL ?
Answer: 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.

Question: Can you give an example of when it would be appropriate to use a web service as opposed to a non-serviced .NET component ?
Answer: When to Use Asp Net Web Services:
(i)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.

(ii)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.

(iii)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.

(iv)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.

Question: What are Service Oriented Architectures (SOA) ?
Answer: SOA describes an information technology architecture that enables distributed computing environments with many different types of computing platforms and applications. Web services in asp net are one of the technologies that help make SOAs possible. As a concept, SOA has been around since the 1980s, but many early IT technologies failed to achieve the goal of linking different types of applications and systems. By making early investments with .NET, Microsoft has helped provide the building blocks that today are putting many enterprise customers on the path to successfully implementing SOAs. With SOAs, companies can benefit from the unimpeded flow of information that is the hallmark of connected systems.

Question: What is .NET Passport ?
Answer: .NET Passport is a Web-based service that is designed to make signing in to Web sites fast and easy. Passport enables participating sites to authenticate a user with a single set of sign-in credentials, alleviating the need for users to remember numerous passwords and user names.

Remoting is the process through which we can access any remote object from one application domain to another application domain.

For creating remote object the class object must be inherited by MarshalByRefObject class.

Application domain is the runtime environment of application, For MicrosoftWord, domain is MS office, For .NET programme, .NET runtime environment.

Terms Used in Remoting

• Proxy: To avoid conjunction in networking. Main work is task Distributing.There are two type of proxy.
  
  
  • Transparent proxy (There is no physical existence , Created by IIS server)
  • Real Proxy (Physical Existence)
  
  
• Channel: Channel provides the medium for transfer data from one location to another location. There are two types of channel.
  
  
  • TCP(work with Predefined root Connection oriented)
  • HTTP (No need predefined root)

3. Formatters: Change the data in an appropriate format that it can traverse through channels.
   
   There are two types of formatters

• Binary
• SOAP(Simple Object Access Protocol)

4. Sink: Sink is used for security point of view. Before sending the data, the Data will be encrypted. Some additional bit will be added with the data to secure the data.
   
   There are two types of sink

• Envoy sink
• Server Context Sink

Object Mode On Server: Two Types of Object Mode .

• SingleCall
• Singleton

application

1. What is .NET Remoting?

   .NET Remoting is an enabler for application communication. It is a generic system for different applications to use to communicate with one another. .NET objects are exposed to remote processes, thus allowing interprocess communication.

2. What’s a Windows process?

   It’s an application that’s running and had been allocated memory.

3. What are the consideration in deciding to use .NET Remoting or ASP.NET Web Services?

   Remoting is a more efficient communication exchange when you can control both ends of the application involved in the communication process. Web Services provide an open-protocol-based exchange of informaion. Web Services are best when you need to communicate with an external organization or another (non-.NET) technology.

4. What are channels in .NET Remoting?

   Channels represent the objects that transfer the other serialized objects from one application domain to another and from one computer to another, as well as one process to another on the same box। A channel must exist before an object can be ट्रांस्फेर्रेड.

5. What security measures exist for .NET Remoting in System.Runtime.Remoting?

   None. Security should be taken care of at the application level. Cryptography and other security techniques can be applied at application or server level.

6. What is a formatter?

   A formatter is an object that is responsible for encoding and serializing data into messages on one end, and deserializing and decoding messages into data on the other end.

7. Can you configure a .NET Remoting object via XML file?

   Yes, via machine.config and application level .config file (or web.config in ASP.NET). Application-level XML settings take precedence over machine.config.

8. Choosing between HTTP and TCP for protocols and Binary and SOAP for formatters, what are the trade-offs?

   Binary over TCP is the most effiecient, SOAP over HTTP is the most interoperable.

9. How do you define the lease of the object?

   By implementing ILease interface when writing the class code.

10. What’s SingleCall activation mode used for?

    If the server object is instantiated for responding to just one single request, the request should be made in SingleCall mode.

more asp.net questiuons

ASP.Net Interview Questions
1. Describe the role of inetinfo.exe, aspnet_isapi.dll andaspnet_wp.exe in the page loading process.
inetinfo.exe is theMicrosoft 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 tothe actual worker process aspnet_wp.exe.

2. What’s the difference between Response.Write() andResponse.Output.Write()?
Response.Output.Write() allows you to write formatted output.

3. 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.

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?
System.Web.UI.Page

6. Where do you store the information about the user’s locale?
System.Web.UI.Page.Culture

7. What’s the difference between Codebehind="MyCode.aspx.cs" andSrc="MyCode.aspx.cs"?
CodeBehind is relevant to Visual Studio.NET only.

8. 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 eventhandlers, allowing the main DataGrid event handler to take care of its constituents.

9. 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.Attributes.Add("onmouseover","someClientCodeHere();");

10. What data types do the RangeValidator control support?
Integer, String, and Date.

11. 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.

12. What type of code (server or client) is found in a Code-Behind class?
The answer is server-side code since code-behind is executed on the server. However, during the code-behind's execution on the server, it can render client-side code such as JavaScript to be processed in the clients browser. But just to be clear, code-behind executes on the server, thus making it server-side code.

13. 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.

14. 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 performas 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.

15. Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?
Valid answers are:
• 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. 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.

19. Whats an assembly?
Assemblies are the building blocks of the .NET framework. Overview of assemblies from MSDN

20. 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.

21. 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.

22. 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.

23. Which method do you invoke on the DataAdapter control to load your generated dataset with data?
The Fill() method.

24. Can you edit data in the Repeater control?
No, it just reads the information from its data source.

25. Which template must you provide, in order to display data in a Repeater control?
ItemTemplate.

26. How can you provide an alternating color scheme in a Repeater control?
Use the AlternatingItemTemplate.

27. 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.

28. What base class do all Web Forms inherit from?
The Page class.

29. Name two properties common in every validation control?
ControlToValidate property and Text property.

30. 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 property.

31. Which control would you use if you needed to make sure the values in two different controls matched?
CompareValidator control.

32. How many classes can a single .NET DLL contain?
It can contain many classes.

Web Service Questions
1. What is the transport protocol you use to call a Web service?
SOAP (Simple Object Access Protocol) is the preferred protocol.

2. True or False: A Web service can only be written in .NET?
False

3. What does WSDL stand for?
Web Services Description Language.

4. Where on the Internet would you look for Web services?
http://www.uddi.org

5. True or False: To test a Web service you must create a Windows application or Web application to consume this service?
False, the web service comes with a test page and it provides HTTP-GET method to test.

State Management Questions
1. 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 the retain the state of server-side objects between postabacks.

2. 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).

3. 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.

4. 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.

OOPs questions

Inheritance

The process of sub-classing a class to extend its functionality is called Inheritance.It provides idea of reusability.

Order of Constructor execution in Inheritance

constructors are called in the order from the top to the bottom (parent to child class) in inheritance hierarchy.

Order of Destructor execution in Inheritance

The destructors are called in the reverse order, i.e., from the bottom to the top (child to parent class) in the inheritance hierarchy.

What are Sealed Classes in C#?
The sealed modifier is used to prevent derivation from a class. A compile-time error occurs if a sealed class is specified as the base class of another class. (A sealed class cannot also be an abstract class)

Can you prevent your class from being inherited by another class?
Yes. The keyword “sealed” will prevent the class from being inherited.

Can you allow a class to be inherited, but prevent the method from being over-ridden?
Yes. Just leave the class public and make the method sealed.

Fast Facts of Inheritance

Multiple inheritance of classes is not allowed in C#.

In C# you can implements more than one interface, thus multiple inheritance is achieved through interface. The Object class defined in the System namespace is implicitly the ultimate base class of all the classes in C# (and the .NET framework)

Structures (struct) in C# does not support inheritance, it can only implements interfaces.

Polymorphism

Polymorphism means same operation may behave differently on different classes.

Eg: Method Overloading is an example of Compile Time Polymorphism.

Method Overriding is an example of Run Time Polymorphism

Does C#.net supports multiple inheritance?

No. A class can inherit from only one base class, however a class can implements many interface, which servers some of the same purpose without increasing complexity.

How many types of Access Modifiers.

1) Public – Allows the members to be globally accessible.

2) Private – Limits the member’s access to only the containing type.

3) Protected – Limits the member’s access to the containing type and all classes derived from the containing type.

4) Internal – Limits the member’s access to within the current project.

Method Overloading

Method with same name but with different arguments is called method overloading.

Method Overloading forms compile-time polymorphism.

Eg:

class A1{

void hello()

{ Console.WriteLine(“Hello”); }

void hello(string s)

{ Console.WriteLine(“Hello {0}”,s); }

}

Method Overriding

Method overriding occurs when child class declares a method that has the same type arguments as a method declared by one of its superclass.

Method overriding forms Run-time polymorphism.

Note: By default functions are not virtual in C# and so you need to write “virtual” explicitly. While by default in Java each function are virtual.

Eg1:

Class parent

{

virtual void hello()

{ Console.WriteLine(“Hello from Parent”); }

}

Class child : parent

{

override void hello()

{ Console.WriteLine(“Hello from Child”); }

}

static void main()

{

parent objParent = new child();

objParent.hello();

}

//Output

Hello from Child.

Virtual Method

By declaring base class function as virtual, we allow the function to be overridden in any of derived class.

Eg:

Class parent

{

virtual void hello()

{ Console.WriteLine(“Hello from Parent”); }

}

Class child : parent

{

override void hello()

{ Console.WriteLine(“Hello from Child”); }

}

static void main()

{

parent objParent = new child();

objParent.hello();

}

//Output

Hello from Child.

What is Interface

· An Interface is a group of constants and method declaration.

· .Net supports multiple inheritance through Interface.

· Interface states “what” to do, rather than “how” to do.

· An interface defines only the members that will be made available by an implementing object. The definition of the interface states nothing about the implementation of the members, only the parameters they take and the types of values they will return. Implementation of an interface is left entirely to the implementing class. It is possible, therefore, for different objects to provide dramatically different implementations of the same members.

· Example1, the Car object might implement the IDrivable interface (by convention, interfaces usually begin with I), which specifies the GoForward, GoBackward, and Halt methods. Other classes, such as Truck, Aircraft, Train or Boat might implement this interface and thus are able to interact with the Driver object. The Driver object is unaware of which interface implementation it is interacting with; it is only aware of the interface itself.

· Example2, an interface named IShape, which defines a single method CalculateArea. A Circle class implementing this interface will calculate its area differently than a Square class implementing the same interface. However, an object that needs to interact with an IShape can call the CalculateArea method in either a Circle or a Square and obtain a valid result.

· Practical Example

public interface IDrivable
{
void GoForward(int Speed);
}

public class Truck : IDrivable
{
public void GoForward(int Speed)
{
// Implementation omitted
}
}

public class Aircraft : IDrivable
{
public void GoForward(int Speed)
{
// Implementation omitted
}
}

public class Train : IDrivable
{
public void GoForward(int Speed)
{
// Implementation omitted
}
}

Extra

· Each variable declared in interface must be assigned a constant value.

· Every interface variable is implicitly public, static and final.

· Every interface method is implicitly public and abstract.

· Interfaces are allowed to extends other interfaces, but sub interface cannot define the methods declared in the super interface, as sub interface is still interface and not class.

· If a class that implements an interface does not implements all the methods of the interface, then the class becomes an abstract class and cannot be instantiated.

· Both classes and structures can implement interfaces, including multiple interfaces.

In which Scenario you will go for Interface or Abstract Class?



Interfaces, like classes, define a set of properties, methods, and events. But unlike classes, interfaces

do not provide implementation. They are implemented by classes, and defined as separate entities from

classes. Even though class inheritance allows your classes to inherit implementation from a base class, it

also forces you to make most of your design decisions when the class is first published.



Abstract classes are useful when creating components because they allow you specify an invariant level

of functionality in some methods, but leave the implementation of other methods until a specific

implementation of that class is needed. They also version well, because if additional functionality is

needed in derived classes, it can be added to the base class without breaking code.

Interview Questions c#

Interview Questions

C#

1. What’s the implicit name of the parameter that gets passed into the class’ set method? Value, and its datatype depends on whatever variable we’re changing.
2. How do you inherit from a class in C#? Place a colon and then the name of the base class. Notice that it’s double colon in C++.
3. Does C# support multiple inheritance? No, use interfaces instead.
4. When you inherit a protected class-level variable, who is it available to? Classes in the same namespace.
5. Are private class-level variables inherited? Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.
6. Describe the accessibility modifier protected internal. It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).
7. C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write? Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.
8. What’s the top .NET class that everything is derived from? System.Object.
9. How’s method overriding different from overloading? When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
10. What does the keyword virtual mean in the method definition? The method can be over-ridden.
11. Can you declare the override method static while the original method is non-static? No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
12. Can you override private virtual methods? No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.
13. Can you prevent your class from being inherited and becoming a base class for some other classes? Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It’s the same concept as final class in Java.
14. Can you allow class to be inherited, but prevent the method from being over-ridden? Yes, just leave the class public and make the method sealed.
15. What’s an abstract class? A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it’s a blueprint for a class without any implementation.
16. When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)? When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
17. What’s an interface class? It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.
18. Why can’t you specify the accessibility modifier for methods inside the interface? They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.
19. Can you inherit multiple interfaces? Yes, why not.
20. And if they have conflicting method names? It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
21. What’s the difference between an interface and abstract class? In the interface all methods must be abstract; in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
22. How can you overload a method? Different parameter data types, different number of parameters, different order of parameters.
23. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor? Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
24. What’s the difference between System.String and System.StringBuilder classes? System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
25. What’s the advantage of using System.Text.StringBuilder over System.String? StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.
26. Can you store multiple data types in System.Array? No.
27. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()? The first one performs a deep copy of the array, the second one is shallow.
28. How can you sort the elements of the array in descending order? By calling Sort() and then Reverse() methods.
29. What’s the .NET datatype that allows the retrieval of data by a unique key? HashTable.
30. What’s class SortedList underneath? A sorted HashTable.
31. Will finally block get executed if the exception had not occurred? Yes.
32. What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
33. Can multiple catch blocks be executed? No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
34. Why is it a bad idea to throw your own exceptions? Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
35. What’s a delegate? A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
36. What’s a multicast delegate? It’s a delegate that points to and eventually fires off several methods.
37. How’s the DLL Hell problem solved in .NET? Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
38. What are the ways to deploy an assembly? An MSI installer, a CAB archive, and XCOPY command.
39. What’s a satellite assembly? When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
40. What namespaces are necessary to create a localized application? System.Globalization, System.Resources.
41. What’s the difference between // comments, /* */ comments and /// comments? Single-line, multi-line and XML documentation comments.
42. How do you generate documentation from the C# file commented properly with a command-line compiler? Compile it with a /doc switch.
43. What’s the difference between and XML documentation tag? Single line code example and multiple-line code example.
44. Is XML case-sensitive? Yes, so and are different elements.
45. What debugging tools come with the .NET SDK? CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
46. What does the This window show in the debugger? It points to the object that’s pointed to by this reference. Object’s instance data is shown.
47. What does assert() do? In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
48. What’s the difference between the Debug class and Trace class? Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
49. Why are there five tracing levels in System.Diagnostics.TraceSwitcher? The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
50. Where is the output of TextWriterTraceListener redirected? To the Console or a text file depending on the parameter passed to the constructor.
51. How do you debug an ASP.NET Web application? Attach the aspnet_wp.exe process to the DbgClr debugger.
52. What are three test cases you should go through in unit testing? Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
53. Can you change the value of a variable while debugging a C# application? Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
54. Explain the three services model (three-tier application). Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
55. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET? SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
56. What’s the role of the DataReader class in ADO.NET connections? It returns a read-only dataset from the data source when the command is executed.
57. What is the wildcard character in SQL? Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
58. Explain ACID rule of thumb for transactions. Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
59. What connections does Microsoft SQL Server support? Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).
60. Which one is trusted and which one is untrusted? Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
61. Why would you use untrusted verificaion? Web Services might use it, as well as non-Windows applications.
62. What does the parameter Initial Catalog define inside Connection String? The database name to connect to.
63. What’s the data provider name to connect to Access database? Microsoft.Access.
64. What does Dispose method do with the connection object? Deletes it from the memory.
65. What is a pre-requisite for connection pooling? Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.

Interview Questions asp.net

Interview Questions
ASP.NET

1. Describe the role of inetinfo.exe, aspnet_isapi.dll andaspnet_wp.exe in the page loading process. inetinfo.exe is theMicrosoft 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 tothe actual worker process aspnet_wp.exe.

2. What’s the difference between Response.Write() andResponse.Output.Write()? The latter one allows you to write formattedoutput.

3. What methods are fired during the page load? Init() - when the pageis instantiated, Load() - when the page is loaded into server memory,PreRender() - the brief moment before the page is displayed to the user asHTML, Unload() - when page finishes loading.

4. Where does the Web page belong in the .NET Framework class hierarchy?System.Web.UI.Page

5. Where do you store the information about the user’s locale? System.Web.UI.Page.Culture

6. What’s the difference between Codebehind="MyCode.aspx.cs" andSrc="MyCode.aspx.cs"? CodeBehind is relevant to Visual Studio.NET only.

7. 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 eventhandlers, allowing the main DataGrid event handler to take care of its constituents.

8. Suppose you want a certain ASP.NET function executed on MouseOver overa certain button. Where do you add an event handler? It’s the Attributesproperty, the Add function inside that property. So btnSubmit.Attributes.Add("onMouseOver","someClientCode();")

9. What data type does the RangeValidator control support? Integer,String and Date.

10. Explain the differences between Server-side and Client-side code? Server-side code runs on the server. Client-side code runs in the clients’ browser.

11. What type of code (server or client) is found in a Code-Behind class? Server-side code.

12. Should validation (did the user enter a real date) occur server-side or client-side? Why? Client-side. This reduces an additional request to the server to validate the users input.

13. What does the "EnableViewState" property do? Why would I want it on or off? It enables the viewstate on the page. It allows the page to save the users input on a form.

14. What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other? Server.Transfer is used to post a form to another page. Response.Redirect is used to redirect the user to another page or site.

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. Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines? This is where you can set the specific variables for the Application and Session objects.

17. If I’m developing an application that must accommodate multiple security levels though secure login and my ASP.NET web application is spanned across three web-servers (using round-robin load balancing) what would be the best approach to maintain login-in state for the users? Maintain the login state security through a database.

18. 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. Base Class Employee. A Manager class could be derived from the Employee base class.

19. Whats an assembly? Assemblies are the building blocks of the .NET framework. Overview of assemblies from MSDN

20. 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.

21. 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. For reading database data to an XML file to be sent to a Web Service.

22. 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.

23. Which method do you invoke on the DataAdapter control to load your generated dataset with data? The .Fill() method

24. Can you edit data in the Repeater control? No, it just reads the information from its data source

25. Which template must you provide, in order to display data in a Repeater control? ItemTemplate

26. How can you provide an alternating color scheme in a Repeater control? Use the AlternatingItemTemplate

27. 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? You must set the DataSource property and call the DataBind method.

28. What base class do all Web Forms inherit from? The Page class.

29. Name two properties common in every validation control? ControlToValidate property and Text property.

30. 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

31. What tag do you use to add a hyperlink column to the DataGrid?

32. What is the transport protocol you use to call a Web service? SOAP is the preferred protocol.

33. True or False: A Web service can only be written in .NET? False

34. What does WSDL stand for? (Web Services Description Language)

35. Where on the Internet would you look for Web services? (http://www.uddi.org)

36. 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 property

37. Which control would you use if you needed to make sure the values in two different controls matched? CompareValidator Control

38. True or False: To test a Web service you must create a windows application or Web application to consume this service? False, the webservice comes with a test page and it provides HTTP-GET method to test.

39. How many classes can a single .NET DLL contain? It can contain many classes.