C-Sharp LinkedIn Skill Assessments: The Ultimate Guide to Questions & Answers for Success
C#
Q1. In which of these situations are interfaces better than abstract classes?
- When you need to define an object type’s characteristics, use an interface. When you need to define an object type’s capabilities, use an abstract class.
- Interfaces are a legacy of older versions of C#, and are interchangeable with the newer abstract class feature.
- When you need a list of capabilities and data that are classes-agnostic, use an interface. When you need a certain object type to share characteristics, use an abstract class.
- You should use both an interface and an abstract class when defining any complex object.
Q2. Which statement is true of delegates?
- Delegates are not supported in the current version of C#
- They cannot be used as callbacks.
- Only variables can be passed to delegates as parameters.
- They can be chained together.
Official documentation: Delegates
Q3. Which choice best defines C#’s asynchronous programming model?
- reactive
- inherited callback
- task-based
- callback-based
Official documentation: Task asynchronous programming model resposta correta –> var contacts = new List
Q4. How would you determine if a class has a particular attribute?
- .
var type = typeof(SomeType);
var attribute = type.GetCustomAttribute<SomeAttribute>();
- .
var typeof(MyPresentationModel).Should().BeDecoratedWith<SomeAttribute>();
- .
Attribute.GetCustomAttribute, typeof(SubControllerActionToViewDataAttribute)
- .
Attribute.GetCustomAttribute(typeof(ExampleController), typeof(SubControllerActionToViewDataAttribute))
Q5. What is the difference between the ref and out keywords?
- Variables passed to specify that the parameter is an output parameter, while ref specifies that a variable may be passed to a function without being initialized.
- Variables passed to ref can be passed to a function without being initialized, while out specifies that the value is a reference value that can be changed inside the calling method.
- Variables passed to out can be passed to a function without being initialized, while ref specifies that the value is a reference value that can be changed inside the calling method.
- Variables passed to ref specify that the parameter is an output parameter, while out specifies that a variable may be passed to a function without being initialized.
Q6. How could you retrieve information about a class, as well as create an instance at runtime?
- reflection
- serialization
- abstraction
- dependency injection
Official documentation: Reflection
Q7. What is this code an example of?
private static object objA;
private static object objB;
private static void performTaskA()
{
lock (objB)
{
Thread.Sleep(1000);
lock (objA) { }
}
}
private static void PerformTaskB()
{
lock (objA)
{
lock (objB) { }
}
}
- a private class that uses multithreading
- multithread coding
- thread mismanagement
- a potential deadlock
Official documentation: Deadlocks and race conditions
Q8. What is the difference between an anonymous type and a regular data type?
- Anonymous types don’t have type names
- Anonymous types can only be static
- Anonymous types can be used only in struts
- Anonymous types don’t work with LINQ.
Official documentation: Anonymous Types
Q9. When would you use a Dictionary rather than an Array type in your application?
- When you need a jagged collection structure
- When you need to store values of the same type
- When you need to store key-value pairs rather than single values
- When you need an ordered, searchable list
Official documentation: Dictionary<TKey,TValue> Class
Q10. What is the difference between a.Equals(b) and a == b?
- The .Equals method compares reference identities while the
==
compares contents. - The .Equals method compares primitive values while
==
compares all values. - The .Equals method compares contents while
==
compares reference identity. - The .Equals method compares reference types while
==
compares primitive value types
Q11. Which choice best describes a deadlock situation?
- when you try to instantiate two objects at the same time in the same class or struct
- when you are trying to execute an action after a user event is registered
- when simultaneous instructions are waiting on each other to finish before executing
- when you try to execute a series of events simultaneously on multiple threads
Official documentation: Deadlocks and race conditions
Q12. How does the async keyword work?
- It allows access to asynchronous methods in the C# API
- It allows thread pooling and synchronous processes in static classes.
- It allows the await keyword to be used in a method
- It allows access to synchronous methods in the C# API
Q13. What is an object in C#?
- a class or struct, including its variables and functions
- a primitive data type that can be created only at compile time
- a value type that can be used only with an abstract class
- an instance of a class or struct that includes fields, properties, and/or methods
Official documentation: Objects
Q14. Which code snippet declares an anonymous type named userData?
-
var<<!---->T> userData = new <<!---->T> { name = "John", age = 32 };
-
var userData = new { name = "John", age = 32 };
-
AType userData = new AType { name = "John", age = 32 };
-
Anonymous<T> userData = new Anonymous<T> { name = "John", age = 32 };
Official documentation: Anonymous Types
Q15. What will be returned when this method is executed?
public void userInput(string charParameters) { }
- Nothing
- a Boolean
- a string variable
- an integer
Q16. In what order would the employee names in this example be printed to the console?
string[] employees = { "Joe", "Bob", "Carol", "Alice", "Will" };
IEnumerable<string> employeeQuery = from person in employees
orderby person
select person;
foreach(string employee in employeeQuery)
{
Console.WriteLine(employee);
}
- ascending
- unordered
- descending
- first in, first out
dotnetpattern: LINQ OrderBy Operator
Q17. Lambda expressions are often used in tandem with which of the following?
- Namespaces
- LINQ
- Type Aliasing
- Assemblies
Official documentation: Language Integrated Query (LINQ) Overview
Q18. What is the correct formatting for single-line and multiline comments?
-
/_/ - Single Line
/_ - Multiline
-
// Multiline
/_ Single Line _/
-
//\* Multiline
/ Single Line
-
// Single Line
/* Multiline */
Q19. How do you make a method in an abstract class overridable?
- Make it public
- Make it static
- Make it private
- Make it virtual
Q20. How would you write code for an integer property called Age with a getter and setter?
- public int Age { get - set }
- public int Age: get set;
- public int Age (get, set );
- public int Age { get; set; }
Official documentation: Using Properties
Q21. What is an abstract class?
- a class that is denoted by the class keyword (can be seen and used by any other class in the system–thus it is by default public)
- something denoted by the abstract keyword and used system-wide; if you want any program to create an object of a class you use the abstract class
- a class that is denoted by the virtual keyword
- a class that can be used only as a base class
Official documentation: Abstract and Sealed Classes and Class Members
Q22. When using a thread pool what happens to a given thread after it finishes its task?
- The thread is destroyed and memory is freed up.
- The thread runs in a loop until the next assignment.
- The thread goes inactive in the background and waits for garbage collection.
- The thread returns to the pool for reuse.
Official documentation: Thread pool characteristics
Q23. Which choice represents a class that inherits behavior from a base class?
- a second base class
- a revised class
- a derived class
- a parent class
Official documentation: Inheritance
Q24. What does operator overloading allow you to do?
- hide built-in operators when necessary
- add methods to be interpreted by the compiler at runtime
- define how enums and other primitive value types work within the rest of the application
- define custom functionality for common operators like addition and equality
Official documentation: Operator overloading
Q25. What is the main purpose of LINQ?
- to delete duplicate data
- to bind namespaces and assemblies
- to query and transform data
- to connect assemblies
Official documentation: Language Integrated Query (LINQ) Overview
Q26. What is the correct syntax for a new generic list of strings named contacts?
- public List
contacts = new List (); - public List(string names) contacts = new List(string names)();
- var contacts = new List
(); - var contacts = new List(string);
Official documentation: List
Q27. What is the difference between throw exceptions and throw clauses?
- Throw clauses fire only at runtime, while throw exceptions can fire at any time.
- Throw exceptions overwrite the stack trace, while throw clauses retain the stack information.
- Throw clauses overwrite the stack trace, while throw exceptions retain the stack information.
- Throw exceptions fire only at runtime, while throw clauses can fire during compile time.
Q28. When an asynchronous method is executed, the code runs but nothing happens other than a compiler warning. What is most likely causing the method to not return anything?
- The return yield statement is missing at the end of the method.
- The method is missing an await keyword in its body.
- The wait keyword is missing from the end of the method.
- The yield keyword is missing from the method.
Official documentation: Starting tasks concurrently
Q29. What are C# events?
- system actions that communicate directly with the compiler at runtime
- actions that execute when the code compiles, generating logs and test output
- actions that generate notifications, which are sent to their registered listeners
- user-only methods that send data to the application’s back end
Official documentation: Introduction to events
Q30. What kind of values can arrays store?
- unordered collections of numeric values
- key-value pairs of any C# supported type
- class and struct instances
- multiple variables, or collections, of the same type
Official documentation: Arrays
Q31. Given this enumeration, how would you access the integer-type value of ‘AppState.Loading’?
enum AppState { OffLine, Loading, Ready }
- string currentState = (string)AppState.Loading;
- string currentState = AppState.Loading.integralVal;
- int currentState = AppState.Loading.rawValue;
- int currentState = (int)AppState.Loading;
Official documentation: Enumeration types
Q32. What character would you use to start a regular expression pattern at a word boundary?
- d
- \a
- \b
- \w
- regular-expressions: Word Boundaries
- Official documentation: Regular Expression Language - Quick Reference
Q33. To conform to the following interface, which of its members need to be implemented?
public interface INameable
{
string FirstName { get; set; }
string LastName { get; }
}
- Both the FirstName and LastName properties need to be implemented.
- Neither, they are both optional.
- Only the LastName property needs to be implemented.
- Only the FirstName property needs to be implemented.
Official documentation: interface
Q34. You’re dealing with multiple assemblies in your program, but are worried about memory allocation. At what point in the program life cycle are assemblies loaded into memory?
- at runtime
- at compile time
- only when required
- only when programmatically loaded
Q35. What is the most accurate description of a regular expression?
- A regular expression is a C# tool used to parse HTML
- A regular expression is a special text string for describing a search pattern.
- A regular expression allows a variable to be passed by reference.
- A regular expression allows a class to conform to the Equatable protocol.
- Official documentation: Regular Expression Language - Quick Reference
- Official documentation: .NET regular expressions
Q36. Why would you use a class field in C#
- To define the behaviors of the class
- To hold information and data contained in the class object
- To communicate between classes and object
- To store the class definition value
Official documentation: Introduction to classes
Q37. When would you use generics in your code?
- to increase code performance
- all of these answers
- when code reuse is a priority
- when type safety is important
Official documentation: Generic classes and methods
Q38. What prints to the console when this code is executed?
public delegate void AuthCallback(bool validUser);
public static AuthCallback loginCallback = Login;
public static void Login()
{
Console.WriteLine("Valid user!");
}
public static void Main(string[] args)
{
loginCallback(true);
}
- Login successful…
- Valid user!
- an error, because the method signature of Login doesn’t match the delegate
- Login successful… Valid user!
Q39. How would you declare a sealed class named User?
- public class User {}
- abstract User {}
- sealed class User {}
- private sealed class User {}
Official documentation: Abstract and Sealed Classes and Class Members
Q40. What is the difference between non-static and static classes?
- non-static classes need to be initialized before use, while static classes do not
- non-static classes are accessible only from an interface while static classes are accessible from anywhere
- non-static classes need to initialize all class members at runtime, while static classes do not
- non-static classes do not need to be initialized while static classes do
Q41. Which characteristic prevents this code from compiling?
public int age="28"
- type safety
- single inheritance
- dependency injection
- multiple inheritance
c-sharpcorner: Type Safety in .NET
Q42. How would you serialize this class?
public class User {}
- Mark the User class with the
DeserializableAttribute
. - Declare the class as
public serializable class User {}
. - Mark the User class with the
SerializableAttribute
attribute. - Declare the class as
private serializable class User {}
.
Official documentation: SerializableAttribute Class
Q43. How would you write a delegate named ResultCallback with an int parameter named responseCode?
- public delegate ResultCallback(int responseCode);
- public delegate void ResultCallback<(int) responseCode>;
- public void delegate ResultCallback<int responseCode>;
- public delegate void ResultCallback(int responseCode);
Official documentation: Delegates
Q44. What is the difference between a static and non-static method?
- non-static methods always need to have a void return type
- non-static methods do not have access to static member variables
- static methods do not have to instantiate an instance of the class to call the method
- static methods always have to be public
Official documentation: Static Members
Q45. What is the correct way to write an event named apiResult based on a delegate named ResultCallback?
- public void event ResultCallback apiResult;
- public event ResultCallback(() -> apiResult);
- public event void ResultCallback
- public event ResultCallback apiResult;
Official documentation: Introduction to events
Q46. When will the code inside finally block be executed in a try-catch statement?
- if there is an error, it won’t execute at all
- between the try and catch blocks
- after the try and catch blocks
- when the finally block overrides the catch block and executes in its place
Official documentation: try-catch
Q47. What method correctly extends the string class?
- public static string IsvalidName(this string i, string value) {}
- public static void IsvalidName(this string i, string value) {}
- public string IsvalidName(this string i, string value) {}
- public void IsvalidName(this string i, string value) {}
Q48. How are C# classes limited?
- They do not support multiple inheritance.
- They support multiple inheritance.
- They can have only a set number of properties.
- They can have only a set number of methods.
Official documentation: Class inheritance
Q49. What function do namespaces perform?
- Namespaces calculate code coverage at runtime.
- Namespaces compile application code together at compile time.
- Namespaces group code together into a single repository.
- Namespaces separate code into groupings, control access, and avoid naming collisions.
Official documentation: namespace
Q50. What is the correct way to write a public property with a private backing field?
- A
private int _password;
pubic int Password = { get; set; }
- B
private int _password;
public int Password = _password;
- C
private int _password;
public int Password
{
get -> _password;
set-> _password = value;
}
- D
private int _password;
public int Password
{
get { return _password; }
set { _password = value; }
}
Official documentation: Using Properties
Q51. What is a thread pool?
- a collection of synchronous methods created during initialization that cannot be reused
- a collection of threads created during initialization that can be reused
- a collection of threads only recognized at compile time that can be reused
- a collection of asynchronous methods created at compile time that cannot be reused
Official documentation: ThreadPool Class
Q52. When an object in C# is serialized, what is it converted to?
- XML
- JSON
- byte stream
- value stream
Official documentation: Serialization
Q53. What is a delegate
- a variable that holds a reference to a value type and its content
- a specific value type that can be used only in callback methods
- a type that holds a reference to a method with a particular parameter list and return type
- a custom variable type that can be used in abstract classes
Official documentation: Delegates
Q54. What are the four keywords associated with exception handling in C#?
- try, catch, valid, invalid
- try, valid, finally, throw
- try, catch, finally, throw
- finally, throw, valid, invalid
Q55. What is the main difference between the is and as operators?
- The is operator checks instance types, while the as operator checks the inherited type.
- The is operator checks primitive data types, while the as operator checks the object type.
- The as operator checks the object type, while the is operator attempts to cast an object to a specific type.
- The is operator checks the object type, while the as operator attempts to cast an object to a specific type.
Q56. What is the difference between finally and finalize blocks?
- The finally block is called during the execution of a try and catch block, while the finalize method is called after garbage collection.
- The finally block is called after the execution of a try and catch block, while the finalize method is called just before garbage collection.
- The finalize block is called before the execution of a try and catch block, while the finally method is called just before garbage collection.
- The finalize block is called during the execution of a try and catch block, while the finally method is called after garbage collection.
Q57. Your application has a value type called username that needs to be able to accept null values, but this is generating compile-time errors. How would you fix this in code?
- Null
username = null; - string? username = null;
- Type
? username = null; - Optional
username = null;
Q58. Which code snippet correctly declares a custom exception named InvalidResponse?
- struct InvalidResponse: Exception {}
- class InvalidResponse: Exception {}
- public Exception InvalidResponse = new Exception ();
- public Exception InvalidResponse () -> Exception;
Official documentation: Exceptions
Q59. How would you write an enum variable called AppState with values for Offline, Loading, and Ready?
- enum AppState = [Offline, Loading, Ready]
- enum AppState {“Offline”, “Loading”, “Ready”}
- enum AppState = {Offline, Loading, Ready}
- enum AppState {Offline, Loading, Ready}
Q60. What is the main difference between a value type and a reference type?
- A value type can be any primitive type, while reference types must be type-agnostic.
- A value type refers to another value, while a reference type refers to a value in memory.
- A value type stores an actual value, while a reference type is a pointer to a value.
- A value type is available only at runtime, while a reference type is available only at compile time.
Q61. What is the difference between the break
and continue
keywords?
- The
break
keyword is used to break out of multiple iteration statements, whilecontinue
can only break out of code blocks that have single iterations. - The
break
keyword literally breaks out of a control flow statement, whilecontinue
ignores the rest of the control statement or iteration and starts the next one. - The
break
keyword literally breaks out of the current control flow code and stops it dead, whilecontinue
keeps executing the code after an exception is thrown. - The
break
keyword jumps out of an iteration and then proceeds with the rest of the control flow code, whilecontinue
stops the executing code dead.
Official documentation: Jump statements
Q62. Which code snippet correctly declares a variable named userId with a public get
and private set
?
-
public int userID <get, set>;
-
public int userID [get, private set];
-
public int userID { get; private set; }
-
public int userID = { public get, private set };
Official documentation: Properties
Q63. What is true about virtual methods?
-
Overriding virtual methods in a derived class is mandatory.
-
Overriding virtual methods in a derived class is not possible.
-
Virtual methods always need a default implementation.
-
Virtual methods cannot have a default implementation.
Q64. What is likely to happen if you have multiple threads accessing the same resource in your program?
-
resource overload
-
thread jumping
-
deadlock and race conditions
-
nothing, since this is what threading is for
Official documentation: race conditions
Q65. How do you indicate that a string might be null?
-
A string cannot be nullable.
-
string? myVariable
-
string myVariable = null
-
string(null) myVariable
Official documentation: nullable value types
Q66. Do you need to declare an out variable before you use it?
-
No, you can declare an out in the parameter list.
-
No, Out variables are no longer part of C#.
-
You must declare it if it is a primitive type.
-
Yes.
Q67. How would you access the last two people in an array named People?
-
People[..^2]
-
You cannot do this in C#.
-
People[..^3]
-
People[^2]
Explain: You can do this in C#. However, none of the above answers are correct. You can access the last two items by using People[^2..]
. Please see issue #3354 for more information.
See also: Official Documentation: Ranges
Q68. When can anonymous types be created?
-
at compile time
-
after runtime
-
at runtime
-
after compile time
C-sharpcorner: Anonymous Types
Q69. What is true about thread multitasking?
-
Thread multitasking allows code to be executed concurrently
-
Thread multitasking allows code to be executed only when handling a user event.
-
Thread multitasking blocks code from being executed simultaneously to guard memory.
-
Thread multitasking adds single-threaded code blocks together.
Official Documentation: Threads
Q70. What accessibility level does this class field have?
private string LastName;
- It can be used by other code only in the same class or struct.
- It can be used by other code in a referenced assembly.
- It can be used only by code contained in a derived class.
- It can be used by other code in the same assembly.
Official Documentation: Accessibility Levels
Q71. How would you correctly declare a jagged array called ‘partyInvites’ with 10 empty elements?
-
string[] partyInvites = new string[10];
-
string[][] partyInvites = new string[10][];
-
string[][] partyInvites = new string[10]();
-
string <[]> partyInvites = new string <[10]>;
Official Documentation: Jagged Arrays
Q72. How could you pause a thread for three seconds?
- Thread.Pause(3000);
- Thread.Resume(-3000);
- Thread.Suspend(3000);
- Thread.Sleep(3000);
Q73. What is wrong with this code?
void MyFunction()
{
{
int a = 10;
int b = 20;
int c = a + b;
}
Console.WriteLine(c);
}
- Variable c is never used; displaying it on the console does not count as usage.
- Variables a and b are never used.
- You cannot place code inside brackets inside another block.
- Variable c no longer exists outside the block.
Q74. Which statement is True?
- All are true.
- None are true.
- string is a value type.
- string is an alias for String
Q75. How would you return more than one value from a method?
- Use either a tuple or an out variable.
- The only way is to use an out variable.
- The only way is to use a tuple.
- This cannot be done
Q76. Which is a valid example of a derived class?
-
public class PremiumUser sub User {}
-
public class PremiumUser: User {}
-
public class PremiumUser -> sub User {}
-
public class User: PremiumUser {}
Q77. What is the correct way to call a static method named DebugString from a static class called InputManager?
-
static InputManager.DebugString();
-
InputManager().DebugString;
-
new InputManager().DebugString();
-
InputManager.DebugString();
Q78. What values can be assigned to this variable?
public string? nickname
- null
- String values
- String values or null
- String values with more than one character
Q79. What is a destructor?
-
a special called automatically whenever an object is created or updated
-
an implicit method called automatically when thread pools are processed concurrently
-
an explicit method called automatically when the compiler starts running
-
a special method called automatically whenever an object is deleted or destroyed
Q80. Which code snippet correctly declares a CustomInt type alias of type Int32?
-
typealias CustomInt = System.Int32;
-
var<T> CustomInt = Int32;
-
using CustomInt = System.Int32;
-
type CustomInt = System<Int32>;
Q81. What is an enumeration type?
-
an object of pass by reference type
-
a value type that cannot hold constants
-
set of named integral constants
-
an object of pass-by-value type
Q82. What is the readonly keyword used for in-field declarations?
-
to declare a member variable that cannot be calculated at runtime
-
to declare a field whose value can be assigned only before the constructor exits
-
to declare a static variable that must be set at compile time
-
to declare a static variable that must be set at runtime
Q83. Which statement is true of C# methods?
-
Methods store variables.
-
Methods are actions that an object can take
-
A method can be used only once per C# file.
-
A method determines the state of a given property.
Official documentation: Methods (C# Programming Guide)
Q84 Which is a valid built-in C# Exception class?
-
ArgumentNullValue
-
InvalidFormatFoundException
-
IndexOutOfPocket
-
ArgumentNullException
Official documentation: ArgumentNullException Class
Q85. What is the purpose of an interface in C#?
- Interfaces are used to store data.
- Interfaces define a contract that classes must adhere to, specifying a set of methods and properties that implementing classes must provide.
- Interfaces are used to create instances of classes.
- Interfaces are used for code organization.
Official Documentation: Interfaces (C# Programming Guide)
Q86. What is the primary purpose of the finally
block in a C# try-catch-finally statement?
- The
finally
block is used to handle exceptions. - The
finally
block is used to define the main logic of the try-catch statement. - The
finally
block is optional and not required in try-catch statements. - The
finally
block is used to ensure that certain code is executed regardless of whether an exception occurs.
Official Documentation: try-catch (C# Reference)
Q87. Which data structure in C# allows you to store key-value pairs and is often used for quick data retrieval?
- ArrayList
- List
- Array
- Dictionary
Official Documentation: Dictionary<TKey, TValue> Class
Q88 The execution of the program begins with?
- Main()
- Get()
- Class()
- Display()
Q89 In C# ‘using’ is a?
- Class
- Directive
- Function
- Keyword
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