Some ASP.Net, WCF, MVC and SQL Interview Questions and Answers

Q.1 What are Left Outer Join, RIGHT Outer and Full Joins in SQL?

In Left outer Join it retrieves all the matching rows from first table with second one, and complete rows from first table (unmatched) too.

In Right outer Join it retrieves all the matching rows from second table with first one, and complete rows from second table (unmatched) too.

In Full Join it retrieves all the matching rows from second table with first one, and complete rows from both the tables (unmatched) too.

Q.2 How to get Highest (nth) & Lowest (nth) Salary?

For 3rd Highest Salary

SELECT TOP 1 marks, name from (SELECT TOP 3 marks, name from MyTable ORDER BY marks ASC) a ORDER BY marks

GO

For 3rd Lowest Salary

SELECT MIN(marks) from (SELECT TOP 3 marks from MyTable ORDER BY marks ASC) a

Q.3 Give an example of Self Join?

The best example of self-join is to get employee with their reporting manager e.g.:

Employee Master Table

id	name	ReportingTo
1	Satish Pal	NULL
2	Suraj Mishra	1
3	Hariom Mishra	NULL
4	Arvind Trivedi	3
5	Ved Pathak	NULL
6	Pradeep Kedare	5

Step 1.

You can find employee with their manager only using simple self –join as:

select A.name, B.name from MyTable A ,MyTable B WHERE B.ID = A.ReportingTo

Step 1.

You can find employee as well as their manager in record  as:

select A.name, ISNULL(B.name,'Manager') as ReportTo from MyTable A LEFT JOIN MyTable B ON B.ID = A.ReportingTo

Q.4 what is major difference between stored procedure and functions?

Procedures	Functions
It is used for select as well as DML(Insert, Update, Delete) operations	It is only used for select operations
It takes input and output both parameters	It takes only input parameters
It cannot be used in select query.	It is used in select query.
Exception handling try, catch can be used	Exception handling try, catch cannot be used
It can call functions	It cannot call procedures
It can return 0 or more values	It is mandatory to return one value

Q.5 what is difference between CHAR, VARCHAR, VARCHAR2 & NVARCHAR?

We must have gone through in interview sometimes with the biggest confusing difference of above questions, as it is very simple but sometimes we get confuse to give right answer to interviewer:

Here I have found the major differences in all:

CHAR	NCHAR
Char is used for fixed length of data type	NChar is used for fixed length of data type
Char takes 1byte memory space for each character	NChar takes 2bytes memory space for each character
Char stores non-Unicode characters	NChar stores Unicode characters
Ex:DECLARE @gender char(10)  SET @gender=’Male’ as variable @gender take only 4 bytes space but it takes full space of 10 bytes when you see actual data length .	Ex:DECLARE @gender nchar(10)  SET @gender=’Male’ as variable @gender take only 4 bytes space but it takes full space of 20 bytes when you see actual data length . It takes double of declared size length.  Here we can use multi languages i.e Hindi, English, Spanish etc.

VARCHAR	NVARCHAR
VarChar is used for variable length of data type	NVarChar is used for variable length of data type
VarChar takes 1byte memory space for each character	NVarChar takes 2bytes memory space for each character
VarChar stores non-Unicode characters	NVarChar stores Unicode characters
Ex:DECLARE @gender varchar(10)  SET @gender=’Male’ as variable @gender take only 4 bytes & actual data length is also only 4 bytes.	Ex: DECLARE @gender nvarchar(10)  SET @gender=’Male’ as variable @gender take only 4 bytes & actual data length is 8 bytes. It takes double of the used memory space. Here we can use multi languages i.e Hindi, English, Spanish etc.

You can use this query to verify the exact space of bytes by below example

DECLARE @gender as char(10)

SET @gender='Male'

SELECT LEN(@gender), DATALENGTH(@gender)

Q.6 what is Serialization and De-serialization?

Process where converting the objects in to stream of bytes is called serialization.

Process where creating the objects from stream of bytes is called De-serialization.

Q.7 what is Garbage collection?

Garbage Collection is also known as automatic memory management, is the automatic recycling of dynamically allocated memory.

In .Net CLR has Garbage Collector that executes as a part of the program in application and responsible for reclaiming the memory of no longer used objects. Garbage collector frees the memory for objects that are no longer used and keeps the memory free for future allocations.

Q.8 what is MSIL?

Q.9 what is the difference between Server.Transfer and Response.Redirect ?

 In asp.net both are used for navigation purpose from source to destination page.

Server.Transfer works for .aspx page only, it does not take round trip back to client browser by processing one page to another.

Response.Redirect works for internal and external both pages (I.e. .aspx page, www.yahoo.com) but it takes round trip back to client browser to complete.

Q.10 what is Globalization and Localization?

Globalization is the process of creating multilingual application by defining culture specific features i.e. Currency, date time format, Language etc.

Localization is the process of cooperating cultural differences in application.

Q.11 what is Partial Class?

When there is a need to keep the business logic separate from the user interface or when there is some class which is big enough to handle by multiple programmers want to implement method from this class, the class can be separate and written in different files as partial class:

As example:

Here is partial class file 1:

///

/// Summary description for myPartialClass1

///

public partial class myPartialClass

{

    public int GetAge()

    {

        int age = 25;

        return age;

    }

}

Here is partial class file 2:

///

/// Summary description for myPartialClass2

///

public partial class myPartialClass

{

    public int GetAge()

    {

        int age = 25;

        return age;

    }

}

You can access both methods as :

myPartialClass objPartial = new myPartialClass();

  string name = objPartial.GetName();

  int age = objPartial.GetAge();

  Response.Write("Name :" + name + " Age :" + age);

Partial classes allow us to divide the class definition into multiple files i.e. (myPartialClass1, myPartialClass2). Although, all the partial classes are treated as a single file by the compiler.

Q.12 what is the difference between Custom Control and User Control?

Custom control are in pre-compiled form i.e (in the form of dll), this can be added into toolbox where most of the inbuilt controls already resides (Textbox, Dropdown etc.). Not easy to customize as per application requirements.

It is ready to use like drag-drop features and reusable to multiple applications.

User Controls are compiled with the application and it is like .aspx page (with .ascx extension) . It is very easy to create and tightly coupled with user interface and code. It is easy to customize as per application requirements.

In order to User Control you have top copy and paste manually to other applications.

Q.13 what is .Net Framework?

A programming infrastructure created by Microsoft for building, deploying, and running applications and services that use .NET technologies, such as desktop applications and Web services. The .NET Framework contains three major parts: the Common Language Runtime. The Framework Class Library

Q.14 How to find out Doctor who has seen most patients by using below table structures?

tblDoctor
doctorID	doctorName
1	Arvind Trivedi
2	Satish Pal
3	Hariom Mishra
4	Vikas Pathak

tblPatient
patientID	doctorID	patientName
1	1	rahul d
2	1	sunil s
3	2	hemant s
4	2	priya s
5	2	nayak s
6	2	ritu p
7	3	umesh
8	3	dinesh
1	1	rahul d
2	1	sunil s

               

Here is the query to get highest number of patient seen by doctor:

SELECT TOP 1 D.doctorName as Doctor, COUNT(P.patientID) as [Patient Count] from tblDoctor D INNER JOIN tblPatient P

ON D.doctorID = P.doctorID

GROUP BY D.doctorName

ORDER BY COUNT(P.patientID) DESC

Q.15 What is Assembly in ASP.Net?

An assembly is a collection of types and resources that forms a logical unit of functionality.

When you compile an application, the MSIL code created is stored in an assembly.

Assemblies include both executable application files that you can run directly from Windows without the need for any other programs (these have a .exe file extension), and libraries (which have a .dll extension) for use by other applications.

There are two types of assemblies in .NET;

1.       Private   2. Shared

Q.16 Difference between ASMX web service and WCF?

There are many options to create we services using .net framework. As web services were used before introducing WCF (indigo). WCF is the latest model to create the web service. There are more advantages over .asmx using WCF. Here will see all comparison on both:

ASMX

Here we defined WebService and WebMethod attributes to define web services.

Support only HTTP, HTTPS protocol.

Hosted only on IIS.

Security is lesser than WCF.

It supports one way and Request-Response Service operations.

Services are little slow compare to WCF.

Unhandled exception return to client.

It does not support multithreading.

WCF

Here we defined Service Contract and Operation Contract attributes to define WCF services.

Support only HTTP, HTTPS, TCP, and Named Pipes and MSMQ protocol.

Hosted on IIS, Self-hosting, WAS (windows Activation Services) and windows service.

Security is more.

It supports one way and Request-Response and Duplex Service operations.

WCF is faster.

Unhandled exception handled by exception handling method using FAULT CONTRACT.

It supports multithreading using Service behaviour class.

Q.17  How to find nth highest, odd numbers, even numbers from integer array value in C# using LINQ?

Most of the time interviewer asked about to writes above query to find out the second highest number, even numbers, and odd numbers from array using LINQ. Here are the simple methods to find out:

int [] i = { 1, 2, 3, 4, 5, 6 };

To find 2^nd highest number from above array:

var highestNums = (from n in i

                       orderby n descending

                       select n).Skip(1).Take(1);

On above query expression   first we take variable in from array order by number in descending and select all the numbers, this is as simple as retrieving all the numbers from array.

The next step to bypass the number from list using SKIP function (as second highest then skip first number from list). And the last to get only that number in the result we used Take function (Take (1)) means it will retrieve only one result, otherwise it gives all the result from the array excluding one record.

To find even numbers from above array:

var evenNums = (from n in i

where (n % 2 == 0)

                       select n);

On above expression it takes all the value from the array and filters it with (%) modulus operator to get only those results which reminder is zero by dividing the even number.

To find odd numbers from above array:

var oddNums = (from n in i

where (n % 2 != 0)

                       select n);

On above expression it takes all the value from the array and filters it with (%) modulus operator to get only those results which reminder is not zero by dividing the even number.

I hope you enjoy the questions and answers!

Please fell free to give me your suggestion/feedback on same.

One more good news for all freshers student we are going to conduct vacation batch for free training cum live demo project session only for freshers, starting from June.

Q.18. How to delete duplicate rows from table?
A: here is explained, how can we delete the duplicate rows from the table where table has no primary key.

CREATE TABLE Employee(empid int,name varchar(20))

   

    INSERT INTO Employee VALUES (1,'Arvind')

    INSERT INTO Employee VALUES (1,'Arvind')

    INSERT INTO Employee VALUES (2,'Pawan')

    INSERT INTO Employee VALUES (2,'Pawan')

    INSERT INTO Employee VALUES (2,'Pawan')

    INSERT INTO Employee VALUES (3,'Ved')

    INSERT INTO Employee VALUES (4,'RamChandra')

   

GO

--Check the number of records

SELECT  * FROM Employee

--Delete duplicate records from the table

;with cte

AS

(

     SELECT ROW_NUMBER() OVER (Partition by empid ORDER BY name) as ID, empid, name FROM Employee

)

DELETE FROM cte WHERE ID>1

People who are interested, enroll yourself by sending your details on vedrajan@gmail.com, as :

name :

address:

contact:

email:

qualification:

location:

Cheers,

ved Pathak