C# Advanced Features u0026 Patterns: Deep Dive Quiz Quiz

Explore advanced C# language features and design patterns with this engaging quiz. Assess your understanding of topics like delegates, LINQ, async programming, extension methods, and other advanced C# constructs in a clear, accessible format.

1. Understanding Delegates

   Which statement correctly describes a delegate in C# and how it is typically used?

   1. A delegate stores application configuration settings.
   2. A delegate is a variable that stores integers for arithmetic operations.
   3. A delegate manages object lifespans in memory.
   4. A delegate is a strongly-typed function pointer used to encapsulate a method reference.

   Explanation: A delegate in C# is a type-safe object that holds a reference to a method, allowing methods to be passed as parameters or assigned to variables. It is similar to a function pointer but with strong type checking. The other options are incorrect because a delegate does not store integers, manage memory, or hold configuration settings; those descriptions refer to other constructs.

2. LINQ Query Basics

   When using LINQ in C#, what is the primary purpose of the 'where' keyword in a query expression?

   1. It projects elements of a collection into a new form.
   2. It reorders the elements of a collection alphabetically.
   3. It filters elements of a collection based on a specified condition.
   4. It removes duplicate elements from a collection.

   Explanation: The 'where' keyword in LINQ expressions is used to specify criteria for filtering items in a sequence, only including those that satisfy the given condition. Sorting is accomplished using 'orderby', removing duplicates requires 'distinct', and projecting into a new form is done with 'select'.

3. Extension Methods

   How are extension methods correctly defined in C# and what is a key requirement for their implementation?

   1. They must be non-static methods defined in any class.
   2. They must be static methods in a static class, with the first parameter preceded by the 'this' modifier.
   3. They must be abstract methods in an interface.
   4. They must be declared as virtual methods in a derived class.

   Explanation: Extension methods extend existing types without modifying the type's source code, and must be static methods inside a static class; the first parameter specifies the extended type and uses the 'this' keyword. Abstract and virtual methods relate to inheritance, not extension methods. Non-static methods cannot be used as extension methods.

4. Async and Await Syntax

   In C#, what does the 'await' keyword do when used with asynchronous methods?

   1. It immediately throws an exception.
   2. It suspends method execution until the awaited task completes.
   3. It compiles code with optimization enabled.
   4. It encrypts the data being processed.

   Explanation: The 'await' keyword pauses the execution of an async method until the awaited operation has finished, enabling asynchronous programming. It does not throw exceptions, compile code, or provide encryption services; these are not functions of the 'await' keyword.

5. Pattern Matching Enhancement

   Which feature was introduced in C# to provide more expressive type checking within switch statements?

   1. Dynamic type inference.
   2. Pattern matching with the 'is' and 'switch' expressions.
   3. Unchecked context declaration.
   4. Explicit interface implementation.

   Explanation: Pattern matching allows more concise and readable type checks and data extractions in switch statements. Unchecked contexts relate to arithmetic overflows. Dynamic type inference is a general concept but not a specific feature, and explicit interface implementation is about interface methods, not pattern matching.

6. Lambda Expressions Usage

   What does the following C# code define? 'Funcu003Cint, int, intu003E add = (x, y) =u003E x + y;'

   1. A lambda expression that takes two integers and returns their sum.
   2. A property that holds the state of two variables.
   3. An array that stores integer values.
   4. A delegate that subtracts two numbers.

   Explanation: This code defines a lambda expression assigned to a Func delegate, which takes two integers as input and returns their sum. The code does not perform subtraction, manage state, or represent an array; those are incorrect interpretations.

7. Readonly Members

   Which keyword can be used in C# to declare a field that can only be assigned once, either at its declaration or in the constructor?

   1. partial
   2. volatile
   3. readonly
   4. sealed

   Explanation: The 'readonly' keyword specifies that a field may be assigned only once outside the constructor or at its declaration, enforcing immutability after construction. 'Sealed' prevents inheritance, 'partial' splits class definitions, and 'volatile' deals with multi-threaded access but not single-assignment properties.

8. Using Statements and IDisposable

   Why is it recommended to use 'using' statements when working with objects that implement IDisposable in C#?

   1. To hide object members from the outside code.
   2. To convert the object into a dynamic type.
   3. To allow multiple inheritance for classes.
   4. To ensure resources are automatically released when the object goes out of scope.

   Explanation: The 'using' statement ensures that resources like file handles or database connections are properly disposed of when the object is no longer needed. It does not convert types, hide members, or affect inheritance; those features are controlled by other language constructs.

9. Auto-implemented Properties

   What is a primary benefit of using auto-implemented properties in C# class definitions?

   1. They provide thread-safe access by default.
   2. They automatically validate all property changes.
   3. They restrict property visibility to private classes only.
   4. They reduce boilerplate code by automatically generating private backing fields.

   Explanation: Auto-implemented properties simplify property declarations by eliminating the need to explicitly define a backing field. They do not validate changes or provide thread safety by default, and visibility dependents on access modifiers, not the property type.

10. Nullable Types

    Which syntax correctly represents a nullable value type for an integer in C#?

    1. int*
    2. int?
    3. int$
    4. nullable int[]

    Explanation: Using 'int?' is the correct shorthand for a nullable integer value type in C#. 'nullable int[]' is invalid syntax, 'int*' indicates a pointer type used in unsafe contexts, and 'int$' is not a recognized type in C#.