C# .NET

Question 1

Can multiple catch blocks be executed?

Answer 1

No, Multiple catch blocks of similar type can’t be executed. Once the proper catch code executed, the control is transferred to the finally block, and then the code that follows the finally block gets executed.

Question 2

What is the difference between public, static, and void?

Answer 2

Public declared variables or methods are accessible anywhere in the application. Static declared variables or methods are globally accessible without creating an instance of the class. Static member are by default not globally accessible it depends upon the type of access modified used. The compiler stores the address of the method as the entry point and uses this information to begin execution before any objects are created. And Void is a type modifier that states that the method or variable does not return any value.

Question 3

What is an Object

Answer 3

An object is an instance of a class through which we access the methods of that class. “new” keyword is used to create an object. A class that creates an object in memory will contain the information about the methods, variables, and behavior of that class.

Question 4

Define Constructors

Answer 4

A constructor is a member function in a class that has the same name as its class. The constructor is automatically invoked whenever an object class is created. It constructs the values of data members while initializing the class.

Question 5

What are Jagged Arrays?

Answer 5

The Array which has elements of type array is called jagged Array. The elements can be of different dimensions and sizes. We can also call jagged Array as an Array of arrays

Question 6

What is the difference between ref & out parameters?

Answer 6

An argument passed as ref must be initialized before passing to the method whereas out parameter needs not to be initialized before passing to a method.

Question 7

What is the use of ‘using’ statement in C#?

Answer 7

The ‘using’ block is used to obtain a resource and process it and then automatically dispose of when the execution of the block completed.

Question 8

What is serialization?

Answer 8

When we want to transport an object through a network, then we have to convert the object into a stream of bytes. The process of converting an object into a stream of bytes is called Serialization. For an object to be serializable, it should implement ISerialize Interface. De-serialization is the reverse process of creating an object from a stream of bytes.

Question 9

Can we use “this” command within a static method?

Answer 9

We can’t use ‘This’ in a static method because we can only use static variables/methods in a static method.

Question 10

What is the difference between constants and read-only?

Answer 10

Constant variables are declared and initialized at compile time. The value can’t be changed afterward. Read-only is used only when we want to assign the value at run time.

Question 11

What is an interface class?

Answer 11

An Interface is an abstract class which has only public abstract methods, and the methods only have the declaration and not the definition. These abstract methods must be implemented in the inherited classes.

Question 12

What are value types and reference types?

Answer 12

A value type holds a data value within its own memory space.

Reference type stores the address of the Object where the value is being stored. It is a pointer to another memory location

Question 13

What are sealed classes in C#?

Answer 13

We create sealed classes when we want to restrict the class to be inherited. Sealed modifier used to prevent derivation from a class. If we forcefully specify a sealed class as base class, then a compile-time error occurs.

Question 14

What is method overloading?

Answer 14

Method overloading is creating multiple methods with the same name with unique signatures in the same class. When we compile, the compiler uses overload resolution to determine the specific method to be invoke.

Question 15

What is the difference between Array and Arraylist?

Answer 15

In an array, we can have items of the same type only. The size of the array is fixed when compared. To an arraylist is similar to an array, but it doesn’t have a fixed size.

Question 16

Can a private virtual method can be overridden?

Answer 16

No, because they are not accessible outside the class.

Question 17

Describe the accessibility modifier “protected internal”

Answer 17

Protected Internal variables/methods are accessible within the same assembly and also from the classes that are derived from this parent class.

Question 18

What are the differences between System.String and System.Text.StringBuilder classes?

Answer 18

System.String is immutable. When we modify the value of a string variable, then a new memory is allocated to the new value and the previous memory allocation released. System.StringBuilder was designed to have a concept of a mutable string where a variety of operations can be performed without allocation separate memory location for the modified string.

Question 19

What’s the difference between the System.Array.CopyTo() and System.Array.Clone()

Answer 19

Using Clone() method, we creates a new array object containing all the elements in the original Array and using CopyTo() method. All the elements of existing array copies into another existing array. Both methods perform a shallow copy.

Question 20

How can we sort the elements of the Array in descending order?

Answer 20

Using Sort() methods followed by Reverse() method.

Question 21

What’s the difference between an interface and abstract class?

Answer 21

Interfaces have all the methods having only declaration but no definition. In an abstract class, we can have some concrete methods. In an interface class, all the methods are public. An abstract class may have private methods.

Question 22

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

Answer 22

Dispose() is called when we want for an object to release any un-managed resources with them. On the other hand, Finalize() is used for the same purpose, but it doesn’t assure the garbage collection of an object.

Question 23

What are circular references?

Answer 23

Circular reference is situation in which two or more resources are interdependent on each other causes the lock condition and make the resources unusable.

Question 24

What are generics in C#.NET?

Answer 24

Generics are used to make reusable code classes to decrease the code redundancy, increase type safety, and performance. Using generics, we can create collection classes. To create generic collection, System.Collections.Generic namespace should be used instead of classes such as ArrayList in the System.Collections namespace. Generics promotes the usage of parameterized types.

Question 25

What is an object pool in .NET?

Answer 25

An object pool is a container having objects ready to be used. It tracks the object that is currently in use, total number of objects in the pool. This reduces the overhead of creating and re-creating objects.

Question 26

List commonly used types of exceptions in .net

Answer 26

ArgumentException, ArgumentNullException, ArgumentOutOfRangeException, ArithmeticException, DivideByZeroException ,OverflowException, IndexOutOfRangeException, InvalidCastException, InvalidOperationException, IOEndOfStreamException , NullReferenceException, OutOfMemoryException, StackOverflowException etc.

Question 27

What are Custom Exceptions?

Answer 27

Sometimes there are some errors that need to be handled as per user requirements. Custom exceptions are used for them and are used defined exceptions.

Question 28

What are delegates?

Answer 28

Delegates are same are function pointers in C++, but the only difference is that they are type safe, unlike function pointers. Delegates are required because they can be used to write much more generic type-safe functions.

Question 29

How do you inherit a class into other class in C#?

Answer 29

Colon is used as inheritance operator in C#. Just place a colon and then the class name.

public class DerivedClass : BaseClass

Question 30

What is the base class in .net from which all the classes are derived from?

Answer 30

System.Object

Question 31

What is the difference between method overriding and method overloading?

Answer 31

In method overriding, we change the method definition in the derived class that changes the method behavior. Method overloading is creating a method with the same name within the same class having different signatures.

Question 32

What are the different ways a method can be overloaded?

Answer 32

Methods can be overloaded using different data types for a parameter, different order of parameters, and different number of parameters.

Question 33

Why can’t you specify the accessibility modifier for methods inside the interface?

Answer 33

In an interface, we have virtual methods that do not have method definition. All the methods are there to be overridden in the derived class. That’s why they all are public

Question 34

How can we set the class to be inherited, but prevent the method from being over-ridden?

Answer 34

Declare the class as public and make the method sealed to prevent it from being overridden.

Question 35

What happens if the inherited interfaces have conflicting method names?

Answer 35

Implement is up to you as the method is inside your own class. There might be a problem when the methods from different interfaces expect different data, but as far as compiler cares you’re okay.

Question 36

What is the difference between a Struct and a Class?

Answer 36

Structs are value-type variables, and classes are reference types. Structs stored on the Stack causes additional overhead but faster retrieval. Structs cannot be inherited.

Question 37

What is difference between “is” and “as” operators in c#?

Answer 37

“is” operator is used to check the compatibility of an object with a given type, and it returns the result as Boolean.

“as” operator is used for casting of an object to a type or a class.

Question 38

What’s a multicast delegate?

Answer 38

A delegate having multiple handlers assigned to it is called multicast delegate. Each handler is assigned to a method.

Question 39

What are indexers in C# .NET?

Answer 39

Indexers are known as smart arrays in C#. It allows the instances of a class to be indexed in the same way as an array.

Question 40

What is difference between the “throw” and “throw ex” in .NET?

Answer 40

“Throw” statement preserves original error stack whereas “throw ex” have the stack trace from their throw point. It is always advised to use “throw” because it provides more accurate error information.

Question 41

What are C# attributes and its significance?

Answer 41

C# provides developers a way to define declarative tags on certain entities, eg. Class, method, etc. are called attributes. The attribute’s information can be retrieved at runtime using Reflection.

Question 42

How to implement a singleton design pattern in C#?

Answer 42

In a singleton pattern, a class can only have one instance and provides an access point to it globally.

public sealed class Singleton
{
  private static readonly Singleton _instance = new Singleton();
}

Question 43

Is C# code is managed or unmanaged code?

Answer 43

C# is managed code because Common language runtime can compile C# code to Intermediate language.