Interview Questions in ASP.NET, C#, VB.NET, SQL, .NET Framework

Here I am posting the interview questions whatever i have faced in my interviews

I have searched for so many websites and gathered information from my friends to answer the questions perfectly. i think these questions are very helpful for the people who are trying to get the job on .NET The most common question for experience persons is

Why would you like to change the company?

1. I am looking for a more challenging career in a firm with a larger employee base such as yours.
2. Keeping in mind my career goals, the time has come for me to move onto the next rung of 
3. the ladder and make a mark for myself. This can be achieved in a company like this.
4. It is just a career move to enhance my knowledge in my own area of interest.
5. After completion of this question only interview will go for further questions

Difference between stored procedure and function

1.  Procedure can return zero or n values whereas function can return one value which is mandatory.
2.  Procedures can have input, output parameters for it whereas functions can have only input parameters.
3.  Procedure allows select as well as DML statement in it whereas function allows only select statement in it.
4.  Functions can be called from procedure whereas procedures cannot be called from function.
5.  Exception can be handled by try-catch block in a procedure whereas try-catch block cannot be used in a function.
6.  We can go for transaction management in procedure whereas we can't go in function.
7.  Procedures cannot be utilized in a select statement whereas function can be embedded in a select statement.

Difference between Abstract and Interface

Abstract Class:

• -Abstract class provides a set of rules to implement next class
• -Rules will be provided through abstract methods
• -Abstract method does not contain any definition
• -While inheriting abstract class all abstract methods must be override
• -If a class contains at least one abstract method then it must be declared as an “Abstract Class”
• -Abstract classes cannot be instantiated, but a reference cannot be created
• -Reference depends on child class object’s memory
• -Abstract classes are also called as “Partial abstract classes”
• -Partial abstract class may contain functions with body and functions without body
• -If a class contains all functions without body then it is called as “Fully Abstract Class” (Interface)

Interface:

• -If a class contains all abstract methods then that class is known as “Interface”
• -Interfaces support like multiple inheritance
• -In interface all methods r public abstract by default
• -Interfaces r implementable
• -Interfaces cannot be instantiated, but a reference can be created

Index types in SQL Server

Clustered Index

Only 1 allowed per table physically rearranges the data in the table to confirm to the index constraints for use on columns that are frequently searched for ranges of data for use on columns with low selectivity.

Non-Clustered Index

Up to 249 allowed per table creates a separate list of key values with pointers to the location of the data in the data pages For use on columns that are searched for single values 

A clustered index is a special type of index that reorders the way records in the table are physically stored. Therefore table can have only one clustered index. The leaf nodes of a clustered index contain the data pages. A non-clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on disk. The leaf node of a non-clustered index does not consist of the data pages. Instead, the leaf nodes contain index rows.

Included Column Index (New in SQL Server 2005) 

In SQL Server 2005, the functionality of non-clustered indexes is extended by adding non-key columns to the leaf level of the non-clustered index. Non-key columns can help to create cover indexes. By including non-key columns, you can create non-clustered indexes that cover more queries. The Database Engine does not consider non-key columns when calculating the number of index key columns or index key size. Non-key columns can be included in non-clustered index to avoid exceeding the current index size limitations of a maximum of 16 key columns and a maximum index key size of 900 bytes. Another advantage is that using non-key column in index we can have index data types not allowed as index key columns generally.

In following example column Filename is varchar(400), which will increase the size of the index key bigger than it is allowed. If we still want to include in our cover index to gain performance we can do it by using the Keyword INCLUDE.

CREATE INDEX IX_Document_Title

ON Production.Document (Title, Revision)

INCLUDE (FileName)

Non-key columns can be included only in non-clustered indexes. Columns can’t be defined in both the key column and they INCLUDE list. Column names can’t be repeated in the INCLUDE list. Non-key columns can be dropped from a table only after the non-key index is dropped first. For Included Column Index to exist there must be at least one key column defined with a maximum of 16 key columns and 1023 included columns.

Avoid adding unnecessary columns. Adding too many index columns, key or non-key as they will affect negatively on performance. Fewer index rows will fit on a page. This could create I/O increases and reduced cache efficiency. More disk space will be required to store the index. Index maintenance may increase the time that it takes to perform modifications, inserts, updates, or deletes, to the underlying table or indexed view.

Another example to test:

Create following Index on Database AdventureWorks in SQL SERVER 2005

USE AdventureWorks

GO

CREATE NONCLUSTERED INDEX IX_Address_PostalCode

ON Person.Address (PostalCode)

INCLUDE (AddressLine1, AddressLine2, City, StateProvinceID)

GO

Test the performance of following query before and after creating Index. The performance improvement is significant.

SELECT AddressLine1, AddressLine2, City, StateProvinceID, PostalCode

FROM Person.Address

WHERE PostalCode BETWEEN '98000'

AND '99999';

GO

Interview questions 

What are differences between Array list and Hash table?

Ans: 1) Hash table store data as name, value pair. While in array only value is store.

2) To access value from hash table, you need to pass name. While in array, to access value, you need to pass index number.

3) you can store different type of data in hash table, say int, string etc. while in array you can store only similar type of data.

What are differences between system.stringbuilder and system.string?

The main difference is system.string is immutable and system.stringbuilder is a mutable. Append keyword is used in string builder but not in system.string.

Immutable means once we created we cannot modified. Suppose if we want give new value to old value simply it will discarded the old value and it will create new instance in memory to hold the new value.

What are the differences between Application object and session object?

Ans: The session object is used to maintain the session of each user. If one user enter in to the application then they get session id if he leaves from the application then the session id is deleted. If they again enter in to the application they get different session id.

But for application object the id is maintained for whole application. 

What are the different types of indexes?

Ans: Two types of indexes are there one is clustered index and non-clustered index

How many types of memories are there in .net? 

Ans: Two types of memories are there in .net stack memory and heap memory

Is it possible to set the session out time manually? 

Ans: Yes we can set the session out time manually in web.config.

What are differences between function and stored procedure?

1) Function returns only one value but procedure returns one or more than one value.

2) Function can be utilized in select statements but that is not possible in procedure.

3) Procedure can have an input and output parameters but function has only input parameters only.

4) Exceptions can be handled by try catch block in procedures but that is not possible in function.

What are the differences between Abstract and interface?

1) Abstract and interfaces cannot be instantiated but we can inherit.

2) Interface contain only declarations no definitions. Abstract contain declarations and definitions.

3) The class which contains only abstract methods is interface class. A class which contains abstract method is called abstract class

4) Public is default access specifier for interface we don’t have a chance to declare other specifiers. In abstract we have chance to declare with any access specifier

What is the difference between primary key and unique key with not null?

Ans: There is no difference between primary key and unique key with not null.

What is boxing and unboxing concepts in .net? 

Ans: Boxing is a process of converting value type into reference type

Unboxing is a process of converting reference type to value type.

What are the differences between value type and reference type?

Ans: Value type contain variable and reference type are not containing value directly in its memory.

Memory is allocated in managed heap in reference type and in value type memory allocated in stack. Reference type ex-class value type-struct, enumeration

Is it possible to host the website from desktop?

Ans: Yes 

Why we go for page rendering in Asp.Net Page life cycle?

Ans: Browser understands an only html control that’s why in page rendering we will convert the aspx controls into html controls.

Write a sample query for self join?

Ans: Select e1.ename, e2.empid from emp e1, emp e2 where e1.empid=e2.mgrid;

Can we change the index of primary key on table?

Ans: No

How to change the name of the table or stored procedure in sql?

Ans: sp_rename oldtablename newtablename

For changing the column name

Sp_rename  ‘tablename.[Oldcolumnname]’,’newcolumnname’,’Column’

Ex:sp_rename ‘tblemp.first’,’namechange’,’Column’

How to find out which index is defined on table?

Ans: sp_helpindex tablename

Can you write the program to find the length of string without using library function?

Ans: for (int i=0; str[i]!=”\n”; i++)

{

Count++;

}

What is the difference between scope_identity() and current_identity()?

Ans: Scope_identity and current _identity both are similar and it will return the last identity value generated in the table.

Scope_Identity will return the identity value in table that is currently in scope

What are difference between GET and POST Methods?

Ans:

GET Method (): 

1) Data is appended to the URL.

2) Data is not secret.

3) It is a single call system

4) Maximum data that can be sent is 256.

5) Data transmission is faster

6) this is the default method for many browsers

POST Method (): 

1) Data is not appended to the URL.

2) Data is Secret

3) it is a two call system.

4) There is no Limit on the amount of data. That is characters any amount of data can be sent.

5) Data transmission is comparatively slow.

6) No default and should be explicitly specified.

What are difference between truncate and delete?

Ans: 1) Delete keep the lock over each row where Truncate keeps the lock on table not on all the row.

2) Counter of the Identity column is reset in Truncate where it is not reset in Delete.

3) Trigger is not fired in Truncate where as trigger is fired in Delete.

4) In TRUNCATE we cannot rollback.

5) In DELETE we can rollback

What is the difference Grid View and between Data Grid (Windows)?

Ans:

1) GridView Control Enables you to add sorting, paging and editing capabilities without writing any code.

2)GridView Control Automatically Supports paging by setting the ‘PagerSetting’ Property.The Page Setting Property supports four Modles 

a. Numeric(by default)

b. Next Previous

c. NumericFirstLast

d. Next PreviousLast

3)It is Used in asp.net

4)GridView Supports RowUpdating and RowUpdated Events.

5)GidView is Capable of Pre-Operations and Post-Operations.

6)GridView Has EditTemplates for this control

7)It has AutoFormat

DataGrid(Windows)

1)DataGid Control raises single Event for operations

2)DataGird Supports the SortCommand Events that occur when a column is Soted.

3)DataGrid Supports UpdataCommand Event that occurs when the UpdateButton is clicked for an item in the grid.

4)DataGrid is used in Windows GUI Application.

5)It doesnot have EditTemplates for this control

6)It doesnot have AutoFormat

If I write System.exit (0); at the end of the try block, will the finally block still execute?

Ans: No in this case the finally block will not execute because when you say system.exit(0),the control immediately goes out of the program, and thus finally never executes.

What are the different levels of State management in ASP.NET?

State management is the process by which you maintain state and page information over multiple requests for the same or different pages.

There are 2 types State Management:

1. Client – Side State Management

This stores information on the client's computer by embedding the information into a Web page, a uniform resource locator (url), or a cookie. The techniques available to store the state information at the client end are listed down below:

a. View State – Asp.Net uses View State to track the values in the Controls. You can add custom values to the view state. It is used by the Asp.net page framework to automatically save the values of the page and of each control just prior to rendering to the page. When the page is posted, one of the first tasks performed by page processing is to restore view state.

b. Control State – If you create a custom control that requires view state to work properly, you should use control state to ensure other developers don’t break your control by disabling view state.

c. Hidden fields – Like view state, hidden fields store data in an HTML form without displaying it in the user's browser. The data is available only when the form is processed.

d. Cookies – Cookies store a value in the user's browser that the browser sends with every page request to the same server. Cookies are the best way to store state data that must be available for multiple Web pages on a web site.

e. Query Strings - Query strings store values in the URL that are visible to the user. Use query strings when you want a user to be able to e-mail or instant message state data with a URL.

2. Server – Side State Management

a. Application State - Application State information is available to all pages, regardless of which user requests a page.

b. Session State – Session State information is available to all pages opened by a user during a single visit.

Both application state and session state information is lost when the application restarts. To persist user data between application restarts, you can store it using profile properties.

Abstract Class:

Abstract class is a class which cannot be instantiated. Class should have “Abstract” key word with the name.  In any one of the method of class having abstract method with in it, then it should be define as abstract class. The class which derived the abstract class should have definition of the abstract method. These classes which derived the abstract class and implement the abstract methods call concrete class.

Abstract class may have the definition of function or may not.  Below is the simple example of an abstract class