Interview Questions

Interview Questions Asp.net,Sql Server,Oops,javascript,wcf,Linq,.net framework

While studying from my college days, am facing many interview questions. Here am sharing the latest list of interview questions with answers. I hope, this will help you to clear your technical interviews.


.Net Framework

In this list, it’s having collection of .net Framework questions with answers. It will help you. .Net Framework

Asp.net
In this list, it’s having collection of Asp.net questions with answers. It will help you. Asp.Net

C#
In this list, it’s having collection of C# questions with answers. It will help you. C#

LINQ
In this list, it’s having collection of LINQ questions with answers. It will help you. LINQ

OOPS
In this list, it’s having collection of OOPS questions with answers. It will help you. OOPS

SQL
In this list, it’s having collection of SQL questions with answers. It will help you. SQL

Web Service
In this list, it’s having collection of Web Service questions with answers. It will help you. Web Service

WCF
In this list, it’s having collection of WCF questions with answers. It will help you. WCF





OOPS

What is mean by Class?
Class is a structure that describes the state (property) and behavior (methods) of the object. It is a template or blueprint to create objects of the class. Class represents the noun and it can be used as type in programming language. eg. Car, Person etc

What is mean by Objects?
Object is an executable copy of a class. State and behavior of the objects are defined by class definition. We can create multiple objects for single class. It is also called as instance of the class. When an object is created from the class, memory will be allocated in RAM. e.g Car- Maruthi, Alto, Zen etc. Person- Ram, Sam, John etc

What is mean by Structure?
Structure is a light-weight class used to create user-defined types containing only public fields. Structure can't have implementation inheritance, but it can have interface inheritance. We cannot modify the default constructors as like a class. Structure is a value type holds their value in memory when they are declared.

What is difference between Class and Structure?
Structure is a light-weight class used to create user-defined types containing only public fields. Structure can't have implementation inheritance, but it can have interface inheritance. We cannot modify the default constructors as like a class. Structure is a value type holds their value in memory when they are declared. 1.Class is Reference type(Reference types hold a reference to an object in memory) - Structure is a Value type(Value types hold their value in memory when they are declared) 2.User can modify default constructor and destructor of class- structure can't modify default constructor 3.Class supports inheritance - Structure will not support inheritance 4.Classes must be instantiated using the new operator - Structure can be instantiated without using the new operator

What are advantages of using private constructor, method, property?
Due to security reason, methods and properties are not exposed outside the class using Private access modifier. For implementing Singleton pattern we go for Private Constructor, so we will not able to create instance. Separate method is used to create and return the instance.

What is mean by Partial class?
It is new features in .Net 2.0; partial classes mean that class definition can be split into multiple physical files. Logically, partial classes do not make any difference to the compiler. The compiler intelligently combines the definitions together into a single class at compile-time.

What are different access modifiers in .Net?
· Private - The type or member can only be accessed by code in the same class or structure. · Protected - The type or member can only be accessed by code in the same class or structure, or in a derived class. · Internal - The type or member can be accessed by any code in the same assembly, but not from another assembly. · Protected Internal - The type or member can be accessed by any code in the same assembly, or by any derived class in another assembly. · Public -The type or member can be accessed by any other code in the same assembly or another assembly that references it.

What is mean by inheritance?
Inheritance is one of the concepts of object-oriented programming, where a new class is created from an existing class. Inheritance class is often referred to as subclasses, comes from the fact that the subclass (the newly created class) contains the attributes and methods of the parent class. This can be used to create a highly specialized hierarchical class structure

What is mean by polymorphism?
Polymorphism means the ability to take more than one form. An operation may exhibit different behaviors in different instances. The behavior depends on the data types used in the operation. Polymorphism is extensively used in implementing Inheritance.

What you mean by Encapsulation?
Encapsulation is the procedure of covering up of data and functions into a single unit and protects the data from the outside world. functions implementation and private variables are hidden from outside world.

What is mean by Delegate?
Delegate is a type that holds a reference to a method or a function. . Once a delegate is assigned a method, it behaves exactly like that method. We can call the method using delegate instead of directly calling the method. Using delegate, we can also pass the parameter and get return value. Any method with matched the signature of the delegate can be assigned. Simply we can say .NET implements the concept of function pointers using delegate.

What is mean by Events?
Events are nothing but a publisher and subscriber model. Any subscriber who is interested in receiving notification from the publisher can subscribe the events. If source event is fired or publisher raises the event, a notification will be send to all subscribers. One publisher can have multiple subscribers. Internally events will try to make use of delegate for this publisher, subscription model.




SQL Server

What is Stored Procedure?
A stored procedure is a named group of SQL statements that have been previously created and stored
in the server database. Stored procedures accept input parameters so that a single procedure can be
used over the network by several clients using different input data. And when the procedure is
modified, all clients automatically get the new version. Stored procedures reduce network traffic and
improve performance. Stored procedures can be used to help ensure the integrity of the database.
e.g. sp_helpdb, sp_renamedb, sp_depends etc.

What is Trigger?
A trigger is a SQL procedure that initiates an action when an event (INSERT, DELETE or UPDATE)
occurs. Triggers are stored in and managed by the DBMS.Triggers are used to maintain the referential integrity of data by changing the data in a systematic fashion. A trigger cannot be called or executed;
the DBMS automatically fires the trigger as a result of a data modification to the associated table.
Triggers can be viewed as similar to stored procedures in that both consist of procedural logic that is
stored at the database level. Stored procedures, however, are not event-drive and are not attached to a specific table as triggers are. Stored procedures are explicitly executed by invoking a CALL to the
procedure while triggers are implicitly executed. In addition, triggers can also execute stored
procedures.

What is View?
A simple view can be thought of as a subset of a table. It can be used for retrieving data, as well as
updating or deleting rows. Rows updated or deleted in the view are updated or deleted in the table the
view was created with. It should also be noted that as data in the original table changes, so does data
in the view, as views are the way to look at part of the original table. The results of using a view are
not permanently stored in the database. The data accessed through a view is actually constructed using
standard T-SQL select command and can come from one to many different base tables or even other
views.

What is Index?
An index is a physical structure containing pointers to the data. Indices are created in an existing table
to locate rows more quickly and efficiently. It is possible to create an index on one or more columns of
a table, and each index is given a name. The users cannot see the indexes, they are just used to speed
up queries. Effective indexes are one of the best ways to improve performance in a database
application. A table scan happens when there is no index available to help a query. In a table scan SQL
Server examines every row in the table to satisfy the query results. Table scans are sometimes
unavoidable, but on large tables, scans have a terrific impact on performance.
Clustered indexes define the physical sorting of a database table’s rows in the storage media. For this
reason, each database table may have only one clustered index.
Non-clustered indexes are created outside of the database table and contain a sorted list of references
to the table itself.

What is the difference between clustered and a non-clustered index?
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 nonclustered 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 nonclustered index does not consist of
the data pages. Instead, the leaf nodes contain index rows.

What is cursors?
Cursor is a database object used by applications to manipulate data in a set on a row-by-row basis,
instead of the typical SQL commands that operate on all the rows in the set at one time.

What's the difference between a primary key and a unique key?
Both primary key and unique enforce uniqueness of the column on which they are defined. But by
default primary key creates a clustered index on the column, where are unique creates a nonclustered
index by default. Another major difference is that, primary key doesn't allow NULLs, but unique key
allows one NULL only.

What is difference between DELETE & TRUNCATE commands?
Delete command removes the rows from a table based on the condition that we provide with a WHERE
clause. Truncate will actually remove all the rows from a table and there will be no data in the table
after we run the truncate command.

Difference between Function and Stored Procedure?
UDF can be used in the SQL statements anywhere in the WHERE/HAVING/SELECT section where as
Stored procedures cannot be.
UDFs that return tables can be treated as another rowset. This can be used in JOINs with other tables.
Inline UDF's can be thought of as views that take parameters and can be used in JOINs and other
Rowset operations.

What types of Joins are possible with Sql Server?
Joins are used in queries to explain how different tables are related. Joins also let you select data from
a table depending upon data from another table.
Types of joins: INNER JOINs, OUTER JOINs, CROSS JOINs. OUTER JOINs are further classified as LEFT
OUTER JOINS, RIGHT OUTER JOINS and FULL OUTER JOINS.

What is the difference between a HAVING CLAUSE and a WHERE CLAUSE?
Specifies a search condition for a group or an aggregate. HAVING can be used only with the SELECT
statement. HAVING is typically used in a GROUP BY clause. When GROUP BY is not used, HAVING
behaves like a WHERE clause. Having Clause is basically used only with the GROUP BY function in a
query. WHERE Clause is applied to each row before they are part of the GROUP BY function in a query.

Three ways to find the count of the number of records in a table
--Select count(*) from tableName
--Select sum(1) from tableName
--Select * from tableName
Select @@RowCount

What is data integrity? Explain constraints?
Data integrity is an important feature in SQL Server. When used properly, it ensures that data is accurate, correct, and valid. It also acts as a trap for otherwise undetectable bugs within applications.
A PRIMARY KEY constraint is a unique identifier for a row within a database table. Every table should
have a primary key constraint to uniquely identify each row and only one primary key constraint can be
created for each table. The primary key constraints are used to enforce entity integrity.
A UNIQUE constraint enforces the uniqueness of the values in a set of columns, so no duplicate values
are entered. The unique key constraints are used to enforce entity integrity as the primary key
constraints.
A FOREIGN KEY constraint prevents any actions that would destroy links between tables with the
corresponding data values. A foreign key in one table points to a primary key in another table. Foreign
keys prevent actions that would leave rows with foreign key values when there are no primary keys
with that value. The foreign key constraints are used to enforce referential integrity.
A CHECK constraint is used to limit the values that can be placed in a column. The check constraints
are used to enforce domain integrity.
A NOT NULL constraint enforces that the column will not accept null values. The not null constraints
are used to enforce domain integrity, as the check constraints.

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