Test for ASP.NET developers

Скоро си тествах познанията с един онлайн тест.

Пускам теста с отговорите, защото самият тест е концептуален и е задължително за един developer да е запознат с ООП и База данни.

This test is designed to test your skills in programming, design and SQL.

Programming

What’s the difference between an abstract class and interface? When would you want to use them?

Abstract class can contain abstract methods, abstract property as well as other members (just like normal class).

Interface can only contain abstract methods, properties but we don’t need to put abstract and public keyword. All the methods and properties defined in Interface are by default public and abstract.

What's the difference between overriding and overloading a method?

Overriding - same method names with same arguments and same return types associated in a class and its subclass.

Overloading - same method name with different arguments, may or may not be same return type written in the same class itself.

What's the difference between protected and internal?

Protected:

A protected member is accessible from within the class in which it is declared

Internal:

Internal types or members are accessible only within files in the same assembly.

What's the difference between a static method and a non-static method?

The static methods can by accessed directly from the class, while non-static methods have to be accessed from an instance

Explain what happens when you pass a "ref" or "out" parameter into a method

Ref tells the compiler that the object is initialized before entering the function, while out tells the compiler that the object will be initialized inside the function

What's the difference between a value-type and a reference type?

Value types are stored directly on the stack.

Value types are always accessed directly

Reference types are stored on the run-time heap

A variable of reference type always contains a reference to a value of that type or a null reference

What does the "readonly" keyword in C# mean?

Marking a field as read-only only means that we cannot change the value of that field

What is the difference between a thread and a process?

Process

Each process provides the resources needed to execute a program

A process has a virtual address

Each process is started with a single thread, often called the primary thread, but can create additional threads from any of its threads

Thread

A thread is the entity within a process that can be scheduled for execution

All threads of a process share its virtual address space and system resources

each thread maintains exception handlers

What is an Interface and how is it different from a Class?

Classes as a template to put the properties and functionalities

A class can contain declarations of the following members:

Constructors, Destructors, Constants, Fields, Methods, Properties

An interface contains only the signatures of methods, delegates or events

The implementation of the methods is done in the class that

implements the interface.

A class that implements an interface can explicitly implement members of

that interface. An explicitly implemented member cannot be accessed through a class instance, but only through an instance of the interface

An interface can inherit from one or more base interfaces

What is Reflection?

Reflection helps us to browse methods, properties and function of a given class or assembly on run time and invoke the methods and functions using reflection

How does the generational garbage collector in the .NET CLR manage object lifetime? What is non-deterministic finalization?

No time ???

What is the difference between Finalize() and Dispose()?

Dispose() is called by the user of an object to indicate that he is finished with it, enabling that object to release any unmanaged resources it holds. Finalize() is called by the run-time to allow an object which has not had Dispose() called on it to do the same

What is lambda expression?

Lambda expressions are similar to anonymous methods

they  can contain expressions and statements, and can be used to create delegates or expression tree types

example: customers.Where(c => c.City == "London");

Design

What is object oriented programming and why developers should use it?

OOP gives us

flexibility

polymorphism

encapsulation

inheritance It makes the coding more organized

What is polymorphism?

Polymorphism. It allows you to invoke derived class methods through a base class reference during run-time. This is handy when you need to assign a group of objects to an array and then invoke each of their methods. They won't necessarily have to be the same object type. However, if they're related by inheritance, you can add them to the array as the inherited type. Then if they all share the same method name, that method of each object can be invoked.

Name all design patterns that you know.

 

Describe MVC pattern.

(Model View Controller) A design pattern used in services architectures

The 'Model' is how the underlying data is structured. The 'View' is what is presented to the user or consumer. The 'Controller' is the element that performs the processing.

 

Describe IOC pattern and dependency injection principle.

 

What is TDD and why developers should use it?

SQL

Explain types of JOINs:

INNER JOIN

inner Join : Two tables having the common column values go with inner join

 

LEFT and RIGHT OUTER JOIN

Left outer join: Taking Left side values of the table checking into right side

Right Outer join:Taking Right side values of the table checking left side

Outer join has two sub types left outer join,Right outer join

FULL JOIN

Full join is combined with left outer join ,Right outer join.

 

CROSS JOIN

cross join is an carteasion product ,its like matrix format

What is a key?

A candidate key?

A Candidate Key can be any column or a combination of columns that can qualify as unique key in database. There can be multiple Candidate Keys in one table. Each Candidate Key can qualify as Primary Key

A primary key?

The PRIMARY KEY constraint uniquely identifies each record in a database table.

Primary keys must contain unique values.

A primary key column cannot contain NULL values.

An alternate key?

It is commonplace in SQL databases to declare a single primary key, the most important unique key. However, there could be further unique keys that could serve the same purpose. These should be marked as 'unique' keys. This is done to prevent incorrect data from entering a table (a duplicate entry is not valid in a unique column) and to make the database more complete and useful. These could be called alternate keys

A foreign key?

A FOREIGN KEY in one table points to a PRIMARY KEY in another table

What is an index and how does it help your database?

create indexes in tables

Indexes allow the database application to find data fast without reading the whole table.

CREATE INDEX index_name

ON table_name (column_name)

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