# 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. - [x] 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. # 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. - [x] They can be chained together. [Official documentation: Delegates](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/delegates/#delegates-overview) # Which choice best defines C#'s asynchronous programming model? - [ ] reactive - [ ] inherited callback - [x] task-based - [ ] callback-based [Official documentation: Task asynchronous programming model](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/async/task-asynchronous-programming-model) # How would you determine if a class has a particular attribute? - [ ] . ```cs var type = typeof(SomeType); var attribute = type.GetCustomAttribute(); ``` - [ ] . ```cs var typeof(MyPresentationModel).Should().BeDecoratedWith(); ``` - [ ] . ```cs Attribute.GetCustomAttribute, typeof(SubControllerActionToViewDataAttribute) ``` - [x] . ```cs Attribute.GetCustomAttribute(typeof(ExampleController), typeof(SubControllerActionToViewDataAttribute)) ``` [Official documentation: Attribute Class](https://docs.microsoft.com/en-us/dotnet/api/system.attribute?view=net-5.0) [Official documentation: Attribute.GetCustomAttribute Method](https://docs.microsoft.com/en-us/dotnet/api/system.attribute.getcustomattribute?view=net-5.0) # What is the difference between the ref and out keywords? - [ ] Variables passed to out 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. - [x] 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. [Official documentation: ref](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/ref) [Official documentation: out parameter modifier](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/out-parameter-modifier) # How could you retrieve information about a class, as well as create an instance at runtime? - [x] reflection - [ ] serialization - [ ] abstraction - [ ] dependency injection [Official documentation: Reflection ](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/reflection) # What is this code an example of? ```cs 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 - [x] a potential deadlock [Official documentation: Deadlocks and race conditions](https://docs.microsoft.com/en-us/dotnet/standard/threading/managed-threading-best-practices#deadlocks-and-race-conditions) # What is the difference between an anonymous type and a regular data type? - [x] 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](https://docs.microsoft.com/en-us/dotnet/csharp/fundamentals/types/anonymous-types) # When would you use a Dictionary rather that an Array type in your application? - [ ] when you need a jagged collection structure - [ ] when you need to store values of the same type - [x] when you need to store key-value pairs rather than single values - [ ] when you need an ordered, searchable list [Official documentation: Dictionary Class](https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.dictionary-2?view=net-5.0) # 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. - [x] The .Equals method compares contents while `==` compares reference identity. - [ ] The .Equals method compares reference type while `==` compares primitive value types # 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 - [x] 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](https://docs.microsoft.com/en-us/dotnet/standard/threading/managed-threading-best-practices#deadlocks-and-race-conditions) # 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. - [x] It allows the await keyword to be used in a method - [ ] It allows access to synchronous methods in the C# API [Official documentation: async](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/async) # 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 - [x] an instance of a class or struct that includes fields, properties, and/or methods [Official documentation: Objects](https://docs.microsoft.com/en-us/dotnet/csharp/fundamentals/object-oriented/objects) # Which code snippet declares an anonymous type named userData? - [ ] `var<T> userData = new <T> { name = "John", age = 32 };` - [x] `var userData = new { name = "John", age = 32 };` - [ ] `AType userData = new AType { name = "John", age = 32 };` - [ ] `Anonymous userData = new Anonymous { name = "John", age = 32 };` [Official documentation: Anonymous Types](https://docs.microsoft.com/en-us/dotnet/csharp/fundamentals/types/anonymous-types) # What will be returned when this method is executed? `public void userInput(string charParameters) { }` - [x] nothing - [ ] a Boolean - [ ] a string variable - [ ] an integer [Official documentation: void](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/void) # In what order would the employee names in this example be printed to the console? ```cs string[] employees = { "Joe", "Bob", "Carol", "Alice", "Will" }; IEnumerable employeeQuery = from person in employees orderby person select person; foreach(string employee in employeeQuery) { Console.WriteLine(employee); } ``` - [x] ascending - [ ] unordered - [ ] descending - [ ] first in, first out [dotnetpattern: LINQ OrderBy Operator](http://dotnetpattern.com/linq-orderby-operator) # Lambda expressions are often used in tandem with which of the following? - [ ] Namespaces - [x] LINQ - [ ] Type Aliasing - [ ] Assemblies [Official documentation: Language Integrated Query (LINQ) Overview](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/linq/) # What is the correct formatting for single line and multiline comments? - [ ] /_/ - Single Line /_ - Multiline - [ ] // Multiline /_ Single Line _/ - [ ] //\* Multiline / Single Line - [x] // Single Line /_ Multiline _/ [w3schools: C# Comments](https://www.w3schools.com/cs/cs_comments.php) # How do you make a method in an abstract class overridable? - [ ] Make it public - [ ] Make it static - [ ] Make it private - [x] Make it virtual [Official documentation: virtual](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/virtual) [Official documentation: abstract](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/abstract) # 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 ); - [x] public int Age { get; set; } [Official documentation: Using Properties](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/using-properties) # 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 - [x] a class that can be used only as base class [Official documentation: Abstract and Sealed Classes and Class Members](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/abstract-and-sealed-classes-and-class-members) # 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 loop until the next assignment. - [ ] The thread goes inactive in the background and waits for garbage collection. - [x] The thread returns to the pool for reuse. [Official documentation: Thread pool characteristics](https://docs.microsoft.com/en-us/dotnet/standard/threading/the-managed-thread-pool#thread-pool-characteristics) # Which choice represents a class that inherits behavior from a base class? - [ ] a second base class - [ ] a revised class - [x] a derived class - [ ] a parent class [Official documentation: Inheritance](https://docs.microsoft.com/en-us/dotnet/csharp/fundamentals/object-oriented/inheritance) # 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 - [x] define custom functionality for common operators like addition and equality [Official documentation: Operator overloading](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/operators/operator-overloading) # What is the main purpose of LINQ? - [ ] to delete duplicate data - [ ] to bind namespaces and assemblies - [x] to query and transform data - [ ] to connect assemblies [Official documentation: Language Integrated Query (LINQ) Overview](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/linq/#query-expression-overview) # 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)(); - [x] var contacts = new List(); - [ ] var contacts = new List(string); [Official documentation: List Class](https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.list-1?view=net-5.0) # What is the difference between throw exceptions and throw clauses? - [ ] Throw clauses fire only at runtime, while throw exceptions can fire at any time. - [x] 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. [Official documentation: throw](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/throw) [c-sharpcorner: Difference Between Throw Exception and Throw Clause](https://www.c-sharpcorner.com/UploadFile/akkiraju/difference-between-throw-exception-and-throw-clause/) # 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. - [x] 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. # 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 - [x] 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](https://docs.microsoft.com/en-us/dotnet/csharp/events-overview) # What kind of values can arrays store? - [ ] unordered collections of numeric values - [ ] key-value pairs of any C# supported type - [ ] class and struct instances - [x] multiple variables, or collections, of the same type [Official documentation: Arrays](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/arrays/) # 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; - [x] int currentState = (int)AppState.Loading; [Official documentation: Enumeration types](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/enum#conversions) # What character would you use to start a regular expression pattern at a word boundary? - [ ] d - [ ] \a - [x] \b - [ ] \w [regular-expressions: Word Boundaries](https://www.regular-expressions.info/wordboundaries.html) [Official documentation: Regular Expression Language - Quick Reference](https://docs.microsoft.com/en-us/dotnet/standard/base-types/regular-expression-language-quick-reference) # To conform to the following interface, which of its members need to be implemented? ```cs public interface INameable { string FirstName { get; set; } string LastName { get; } } ``` - [x] 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](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/interface) # 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 - [x] only when required - [ ] only when programmatically loaded # What is most accurate description of a regular expression? - [ ] A regular expression is a C# tool used to parse HTML - [x] A regular expression is a special text string for describing a search patters. - [ ] 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](https://docs.microsoft.com/en-us/dotnet/standard/base-types/regular-expression-language-quick-reference) [Official documentation: .NET regular expressions](https://docs.microsoft.com/en-us/dotnet/standard/base-types/regular-expressions) # Why would you use a class field in C# - [ ] To define behaviours of the class - [x] 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](https://docs.microsoft.com/en-us/dotnet/csharp/fundamentals/types/classes) # When would you use generics in your code? - [ ] to increase code performance - [x] all of these answers - [ ] when code reuse is a priority - [ ] when type safety is important [Official documentation: Generic classes and methods](https://docs.microsoft.com/en-us/dotnet/csharp/fundamentals/types/generics) # What prints to the console when this code is executed? ```cs 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! - [x] an error, because the method signature of Login doesn't match the delegate - [ ] Login successful... Valid user! [Official documentation: Introduction to Delegates](https://docs.microsoft.com/en-us/dotnet/csharp/delegates-overview) [Official documentation: Introduction to Events](https://docs.microsoft.com/en-us/dotnet/csharp/events-overview) # How would you declare a sealed class named User? - [ ] public class User {} - [ ] abstract User {} - [x] sealed class User {} - [ ] private sealed class User {} [Official documentation: Abstract and Sealed Classes and Class Members](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/abstract-and-sealed-classes-and-class-members) # What is the difference between non-static and static classes? - [x] 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 [stackoverflow](https://stackoverflow.com/questions/20451554/whats-the-function-of-a-static-constructor-in-a-non-static-class) [Official documentation: Static Constructors](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/static-constructors) # Which characteristic prevents this code from compiling? `public int age="28"` - [x] type safety - [ ] single inheritance - [ ] dependency injection - [ ] multiple inheritance [c-sharpcorner: Type Safety in .NET](https://www.c-sharpcorner.com/UploadFile/vikie4u/type-safety-in-net/) # How would you serialize this class? `public class User {}` - [ ] Mark the User class with the `DeserializableAttribute`. - [ ] Declare the class as `public serializable class User {}`. - [x] Mark the User class with the `SerializableAttribute` attribute. - [ ] Declare the class as `private serializable class User {}`. [Official documentation: SerializableAttribute Class](https://docs.microsoft.com/en-us/dotnet/api/system.serializableattribute?view=net-5.0) # 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\; - [x] public delegate void ResultCallback(int responseCode); [Official documentation: Delegates](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/delegates/) # 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 - [x] 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](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/static-classes-and-static-class-members#static-members) # 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 - [x] public event ResultCallback apiResult; [Official documentation: Introduction to events](https://docs.microsoft.com/en-us/dotnet/csharp/events-overview) # 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 - [x] after the try and catch blocks - [ ] when the finally block overrides the catch block and executes in its place [Official documentation: try-catch](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/try-catch) # What method correctly extends the string class? - [x] 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) {} # How are C# classes limited? - [x] 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](https://docs.microsoft.com/en-us/dotnet/csharp/fundamentals/types/classes#class-inheritance) # 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. - [x] Namespaces separate code into groupings, control access, and void naming collisions. [Official documentation: namespace](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/namespace) # What is the correct way to write a public property with a private backing field? - [ ] ```cs private int _password; pubic int Password = { get; set; } ``` - [ ] ```cs private int _password; public int Password = _password; ``` - [ ] ```cs private int _password; public int Password { get -> _password; set-> _password = value; } ``` - [x] ```cs private int _password; public int Password { get { return _password; } set { _password = value; } } ``` [Official documentation: Using Properties](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/using-properties) # What is a thread pool? - [ ] a collection of synchronous methods created during initialization that cannot be reused - [x] 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](https://docs.microsoft.com/en-us/dotnet/api/system.threading.threadpool?view=net-5.0) # When an object in C# is serialized, what is it converted to? - [ ] XML - [ ] JSON - [x] byte stream - [ ] value stream [Official documentation: Serialization](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/serialization/) # 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 - [x] 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](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/delegates/) # What are the four keywords associated with exception handling in C#? - [ ] try, catch, valid, invalid - [ ] try, valid, finally, throw - [x] try, catch, finally, throw - [ ] finally, throw, valid, invalid [Tutorial Point](https://www.tutorialspoint.com/csharp/csharp_exception_handling.htm#:~:text=Exceptions%20provide%20a%20way%20to,catch%2C%20finally%2C%20and%20throw.) # 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 object type, while the is operator attempts to cast an object to a specific type. - [x] The is operator checks object type, while the as operator attempts to cast an object to a specific type. [Pluralsight guide](https://www.pluralsight.com/guides/csharp-is-as-operators-is-expressions) # 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. - [x] 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. [C-sharpcorner](https://www.c-sharpcorner.com/forums/final-finally-and-finalize) # 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; - [x] string? username = null; - [ ] Type? username = null; - [ ] Optional username = null; # Which code snippet correctly declares a custom exception named InvalidResponse? - [ ] struct InvalidResponse: Exception {} - [x] class InvalidResponse: Exception {} - [ ] public Exception InvalidResponse = new Exception (); - [ ] public Exception InvalidResponse () -> Exception; [Official documentation: Exceptions](https://docs.microsoft.com/en-us/dotnet/standard/exceptions/how-to-create-user-defined-exceptions) # 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} - [x] enum AppState {Offline, Loading, Ready} [Official documentation: Enum](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/enum) # 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. - [x] 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. [Official documentation: Value types](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/value-types) [Official documentation: Reference types](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/reference-types) # What is the difference between the `break` and `continue` keywords? - [ ] The `break` keyword is used to break out of multiple iteration statements, while `continue` can only break out of code blocks that have single iterations. - [x] The `break` keyword literally breaks out of a control flow statement, while `continue` 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, while `continue` 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, while `continue` stops the executing code dead. [Official documentation: Jump statements](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/statements/jump-statements) # Which code snippet correctly declares a variable named userId with a public `get` and private `set`? - [ ] `public int userID ;` - [ ] `public int userID [get, private set];` - [x] `public int userID { get; private set; }` - [ ] `public int userID = { public get, private set };` [Official documentation: Properties](https://docs.microsoft.com/en-us/dotnet/csharp/properties) # 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.` - [x] `Virtual methods always need a default implementation.` - [ ] `Virtual methods cannot have default implementation.` [Official documentation: virtual](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/virtual) [c-sharpcorner: Virtual Method in C#](https://www.c-sharpcorner.com/UploadFile/3d39b4/virtual-method-in-C-Sharp/) # What is likely to happen if you have multiple threads accessing the same resource in your program? - [ ] `resource overload` - [ ] `thread jumping` - [x] `deadlock and race conditions` - [ ] `nothing, since this is what threading is for` [Official documentation: race conditions](https://docs.microsoft.com/en-us/archive/msdn-magazine/2008/october/concurrency-hazards-solving-problems-in-your-multithreaded-code) # How do you indicate that a string might be null? - [ ] `A string cannot be nullable.` - [x] `string? myVariable` - [ ] `string myVariable = null` - [ ] `string(null) myVariable` # Do you need to declare an out variable before you use it? - [x] `No, you can declare it in the parameter list.` - [ ] `Out variables are no longer part of C#.` - [ ] `You must declare it if it is a primitive type.` - [ ] `Yes.` # How would you access the last two people in an array named People? - [x] `People[..^2]` - [ ] `You cannot do this in C#.` - [ ] `People[..^3]` - [ ] `People[^2]` [Official Documentation: Ranges](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/csharp-8.0/ranges) # When can anonymous types be created? - [x] `at compile time` - [ ] `after runtime` - [ ] `at runtime` - [ ] `after compile time` [C-sharpcorner: Anonymous Types](https://www.c-sharpcorner.com/UploadFile/ff2f08/anonymous-types-in-C-Sharp/) # What is true about thread multitasking? - [x] `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](https://docs.microsoft.com/en-us/dotnet/standard/threading/threads-and-threading) # What accessibility level does this class field have ? `private string LastName;` - [x] 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](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/accessibility-levels) # How would you correctly declare a jagged array called 'partyInvites' with 10 empty elements? - [ ] `string[] partyInvites = new string[10];` - [x] `string[][] partyInvites = new string[10][];` - [ ] `string[][] partyInvites = new string[10]();` - [ ] `string <[]> partyInvites = new string <[10]>;` [Official Documentation: Jagged Arrays](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/arrays/jagged-arrays)