C# is a modern, object-oriented programming language developed by Microsoft, widely used for a variety of software applications.
2. Which of the following is a correct variable declaration in C#?
a) int number = 5;
b) integer number = 5;
c) num number = 5;
d) number: int = 5;
Answer:
a) int number = 5;
Explanation:
In C#, variables are declared with a type (int, in this case), followed by the variable name and an optional assignment.
3. What is the entry point of a C# console application?
a) Main()
b) Start()
c) Program()
d) Init()
Answer:
a) Main()
Explanation:
The Main() method is the entry point of a C# console application, where the program execution begins.
4. How do you create a single-line comment in C#?
a) /* Comment */
b) <!– Comment –>
c) # Comment
d) // Comment
Answer:
d) // Comment
Explanation:
In C#, single-line comments are created using two forward slashes (//).
5. What is the correct way to declare a constant in C#?
a) constant double PI = 3.14;
b) const double PI = 3.14;
c) double const PI = 3.14;
d) define PI = 3.14;
Answer:
b) const double PI = 3.14;
Explanation:
Constants in C# are declared using the 'const' keyword followed by the data type and the constant name.
6. Which keyword is used to define a class in C#?
a) class
b) Class
c) object
d) struct
Answer:
a) class
Explanation:
The 'class' keyword is used to define a class in C#.
7. How do you handle exceptions in C#?
a) using
b) try-catch
c) if-else
d) switch-case
Answer:
b) try-catch
Explanation:
Exceptions in C# are handled using a try-catch block, where 'try' contains the code that might throw an exception, and 'catch' is used to handle the exception.
8. Which collection type automatically resizes in C#?
a) Array
b) List
c) HashSet
d) Queue
Answer:
b) List
Explanation:
The List<> collection in C# automatically resizes as elements are added or removed.
9. How do you concatenate strings in C#?
a) Using the '+' operator
b) Using the '&' operator
c) Using the concat() method
d) Using the append() method
Answer:
a) Using the '+' operator
Explanation:
Strings can be concatenated using the '+' operator in C#.
10. What is LINQ in C#?
a) A database
b) A collection of tools for handling XML
c) A query syntax for querying data sources
d) A method for remote data access
Answer:
c) A query syntax for querying data sources
Explanation:
LINQ (Language Integrated Query) is a feature in C# that provides a query syntax for querying data sources like arrays, collections, databases, etc.
11. What is the output of the following code?
int x = 5;
int y = x++;
a) x=5, y=5
b) x=6, y=5
c) x=5, y=6
d) x=6, y=6
Answer:
b) x=6, y=5
Explanation:
The post-increment operator (x++) increases x after its current value has been assigned to y. So, y gets 5, and then x becomes 6.
12. What is an interface in C#?
a) A method to connect to databases
b) A class that provides default method implementations
c) A template that defines a contract for classes
d) A special type of enumeration
Answer:
c) A template that defines a contract for classes
Explanation:
An interface in C# defines a contract (a set of method and property definitions) that implementing classes must adhere to.
13. What does the 'static' keyword denote in C#?
a) That a method or variable belongs to an instance of a class
b) That a method or variable belongs to the class itself, rather than an instance
c) That a method cannot be overridden in a derived class
d) That a variable will retain its value between method calls
Answer:
b) That a method or variable belongs to the class itself, rather than an instance
Explanation:
The 'static' keyword in C# denotes that a member (method or variable) belongs to the class itself, rather than to any specific instance of the class.
14. Which of the following data types is a reference type in C#?
a) int
b) double
c) string
d) bool
Answer:
c) string
Explanation:
In C#, strings are reference types, whereas int, double, and bool are value types.
15. How do you declare an array in C#?
a) int array[5];
b) int[] array = new int[5];
c) array int[5];
d) new int[5] array;
Answer:
b) int[] array = new int[5];
Explanation:
In C#, arrays are declared with the type followed by square brackets, then the variable name, and finally the 'new' keyword with the array size.
16. What is the purpose of the 'using' directive in C#?
a) To include a namespace in the file
b) To handle exceptions
c) To define a scope at the end of which an object will be disposed
d) To create an alias for a class
Answer:
a) To include a namespace in the file
Explanation:
The 'using' directive in C# is used to include a namespace in a file, allowing the use of types defined in that namespace.
17. What does the 'void' keyword signify in a method declaration?
a) The method returns an integer
b) The method does not return a value
c) The method returns a boolean value
d) The method returns an object
Answer:
b) The method does not return a value
Explanation:
In C#, the 'void' keyword in a method declaration indicates that the method does not return any value.
18. What are generics in C#?
a) Specific types of collections
b) A feature that allows methods and classes to operate with generic parameters
c) A tool for generating code
d) A library for mathematical operations
Answer:
b) A feature that allows methods and classes to operate with generic parameters
Explanation:
Generics in C# allow the creation of methods and classes with the flexibility to work with any data type (specified as a generic parameter).
19. How do you implement inheritance in C#?
a) By using the ':' operator
b) By using the 'extends' keyword
c) By using the 'inherits' keyword
d) By using the 'base' keyword
Answer:
a) By using the ':' operator
Explanation:
Inheritance in C# is implemented by using the ':' operator followed by the base class name.
20. What is a delegate in C#?
a) A data type representing references to methods
b) A method that delegates tasks
c) A reference to an object
d) A type of class that handles events
Answer:
a) A data type representing references to methods
Explanation:
A delegate in C# is a type that represents references to methods with a particular parameter list and return type.
21. What is the scope of a variable declared inside a method in C#?
a) Global
b) Class-wide
c) Local to the method
d) Local to the assembly
Answer:
c) Local to the method
Explanation:
Variables declared inside a method in C# have a scope that is local to the method.
22. What is a constructor in C#?
a) A method used to create objects
b) A special method called when an object is created
c) A method used to initialize variables
d) A method used to destroy objects
Answer:
b) A special method called when an object is created
Explanation:
A constructor is a special method in C# that is called automatically when an instance of a class is created. It is used to initialize the object.
23. What are properties in C#?
a) Special methods used to access and modify fields
b) Constants within a class
c) Variables defined in a class
d) Static methods of a class
Answer:
a) Special methods used to access and modify fields
Explanation:
Properties in C# are special methods that provide a way to read, write, or compute values of private fields.
24. How can you make a class abstract in C#?
a) By using the 'abstract' keyword
b) By using the 'virtual' keyword
c) By not implementing any methods
d) By using the 'static' keyword
Answer:
a) By using the 'abstract' keyword
Explanation:
In C#, a class is made abstract by using the 'abstract' keyword, which means it cannot be instantiated directly and must be inherited.
25. What does 'namespace' represent in C#?
a) A class for networking operations
b) A container for related classes and interfaces
c) A method for handling file operations
d) A data type for storing collections
Answer:
b) A container for related classes and interfaces
Explanation:
A namespace in C# provides a way to logically organize your code. It is a container for classes, interfaces, structs, and other namespaces.
26. How do you handle a null reference exception in C#?
a) Using try-catch blocks
b) Using if-else statements
c) By checking for null before using an object
d) All of the above
Answer:
d) All of the above
Explanation:
Handling null reference exceptions can be done using try-catch blocks for exception handling, using if-else statements to check for null before accessing members, or a combination of both.
27. What is the purpose of the 'ToString' method in C#?
a) To convert any object to its equivalent string representation
b) To change the value of an object
c) To serialize an object
d) To check if an object is a string
Answer:
a) To convert any object to its equivalent string representation
Explanation:
The 'ToString' method is used to convert an object to its string representation, and it can be overridden to provide meaningful string output for a class.
28. How are method parameters passed in C# by default?
a) By reference
b) By value
c) By pointer
d) By name
Answer:
b) By value
Explanation:
In C#, method parameters are passed by value by default. This means a copy of the value is passed to the method.
29. What is the purpose of the 'ref' keyword in method parameters?
a) To pass an argument by reference
b) To indicate a return value
c) To mark a parameter as optional
d) To improve performance
Answer:
a) To pass an argument by reference
Explanation:
The 'ref' keyword is used in C# to pass a parameter by reference, allowing the method to modify the original variable.
30. What is an indexer in C#?
a) A method for incrementing numbers
b) A way to access elements in a class that represents a collection
c) A special type of constructor
d) A tool for sorting collections
Answer:
b) A way to access elements in a class that represents a collection
Explanation:
Indexers in C# provide a way to access elements in an object that represents a collection using array-like syntax.
31. What are events in C#?
a) Error messages generated by the runtime
b) Messages sent by the operating system
c) Actions recognized by an object, like clicks or key presses
d) Scheduled tasks in an application
Answer:
c) Actions recognized by an object, like clicks or key presses
Explanation:
Events in C# are a way for an object to notify other objects when something of interest occurs, such as user interactions.
32. What is the purpose of the 'out' keyword in method parameters?
a) To optimize the method's performance
b) To pass a parameter by value
c) To indicate that a parameter will be used to return a value from the method
d) To declare an external method
Answer:
c) To indicate that a parameter will be used to return a value from the method
Explanation:
The 'out' keyword is used for parameters that the method will use to return data back to the caller.
33. What is a namespace alias in C#?
a) An alternative name for a namespace
b) A shortcut to a frequently used class
c) A way to rename classes
d) A feature for linking libraries
Answer:
a) An alternative name for a namespace
Explanation:
A namespace alias in C# allows you to provide an alternative name for a namespace, simplifying code when dealing with namespaces having long names.
34. What is the use of the 'partial' keyword in C#?
a) To allow a class to be partially implemented
b) To indicate that a class or method is incomplete
c) To split the definition of a class, struct, or method across multiple files
d) To mark a class as abstract
Answer:
c) To split the definition of a class, struct, or method across multiple files
Explanation:
The 'partial' keyword allows the definition of a class, struct, or method to be divided across multiple files, facilitating better organization and maintainability.
35. What is boxing in C#?
a) Encrypting data
b) Converting a value type to a reference type
c) Packaging data into an array
d) Sending data over a network
Answer:
b) Converting a value type to a reference type
Explanation:
Boxing in C# is the process of converting a value type (like int or double) to a reference type, typically to an Object or to an interface type.