Multithreading and Task Parallelism in C#: Concepts and Basics Quiz Quiz

Explore foundational concepts of multithreading and task parallelism in C# with these easy questions tailored for beginners. This quiz covers thread creation, synchronization, task management, and key related terminology important for efficient and safe concurrent programming in C#.

1. Thread Creation

   Which method is commonly used to start a new thread in C# for concurrent execution of code?

   1. Task.Begin()
   2. Thread.Start()
   3. Thread.Launch()
   4. Task.BeginInvoke()

   Explanation: Thread.Start() is the standard method to begin execution of a new thread in C#. Thread.Launch() and Task.BeginInvoke() are not valid methods for thread initiation. Task.Begin() does not exist either; the correct methods with the Task class involve Task.Run or Task.Start. Always ensure you use accurate method names to avoid errors.

2. Task-Based Asynchronous Pattern

   In C#, which class is primarily used to represent an asynchronous operation that can be awaited?

   1. Processor
   2. Thread
   3. Queue
   4. Task

   Explanation: Task is the main class in C# used for representing asynchronous operations and supports being awaited for completion. Thread is used for lower-level management of threads but isn't directly awaitable. Processor and Queue are unrelated to asynchronous operation representation. Using Task helps simplify and manage parallel operations effectively.

3. Race Condition Scenario

   What is a race condition in the context of multithreading in C#?

   1. When a single thread takes too long to process data
   2. When tasks are processed on a queue in order
   3. When two threads attempt to access and modify shared data simultaneously
   4. When a thread is suspended indefinitely

   Explanation: A race condition occurs when two or more threads attempt to access and modify shared data at the same time, potentially leading to corrupted results. A single thread taking too long is just a performance issue, not a race condition. Processing tasks on a queue relates to task scheduling, not thread interference. A suspended thread isn't specifically indicative of a race condition.

4. Locking Mechanism

   Which keyword in C# is used to prevent multiple threads from entering a critical section at the same time?

   1. secure
   2. threadsafe
   3. protect
   4. lock

   Explanation: The lock keyword in C# ensures that only one thread can enter a critical section, preventing data corruption. threadsafe, protect, and secure are not recognized C# keywords for this purpose. They may sound related to security or safety but do not provide synchronization by themselves.

5. Thread Pool Utilization

   What is the main advantage of using a thread pool in C# compared to creating new threads for each task?

   1. Threads in the pool run faster
   2. Pool threads always run on a single core
   3. Pools ignore system resource limits
   4. Reuse of threads reduces overhead

   Explanation: Thread pools reduce the overhead of creating and destroying threads by reusing existing ones. Pool threads do not inherently run faster than regular threads; they just avoid startup costs. Pools still respect system resource limitations, and threads can run on multiple cores. Efficient reuse is the key benefit.

6. Task Parallel Library

   Which namespace in C# contains core types for working with tasks and parallelism?

   1. System.Threads.Parallel
   2. System.Async
   3. System.Concurrency
   4. System.Threading.Tasks

   Explanation: System.Threading.Tasks holds classes such as Task, Parallel, and related constructs for parallel programming. System.Concurrency and System.Async are not valid C# namespaces, and System.Threads.Parallel does not exist. Always use System.Threading.Tasks for task parallelism.

7. Thread Safe Collections

   Which collection should be used in C# when multiple threads need to safely add or remove items concurrently?

   1. ArrayList
   2. List
   3. HashSet
   4. ConcurrentQueue

   Explanation: ConcurrentQueue is designed for safe access when multiple threads perform operations at the same time. List, ArrayList, and HashSet are not thread-safe and can cause issues if modified from multiple threads. Using ConcurrentQueue helps avoid data corruption during concurrent access.

8. Cancelling Tasks

   Which C# object can be used to request cancellation of one or more running tasks?

   1. TaskKiller
   2. CancellationTokenSource
   3. ThreadTerminator
   4. Stopwatch

   Explanation: CancellationTokenSource issues tokens that tasks can observe for cancellation requests. TaskKiller and ThreadTerminator are not actual C# classes or standard concepts, and Stopwatch is used for measuring elapsed time. Proper task cancellation is enabled by CancellationTokenSource.

9. Thread.Sleep Purpose

   What is the primary purpose of using Thread.Sleep(milliseconds) in C# multithreading?

   1. Terminate a thread immediately
   2. Force the processor to switch threads
   3. Pause the current thread for a specified time
   4. Increase thread execution priority

   Explanation: Thread.Sleep pauses execution of the current thread for the given number of milliseconds. It does not end a thread, switch processor contexts directly, or adjust thread priority. Using Thread.Sleep can sometimes help simulate delays or give other threads a chance to run.

10. Task Continuation Example

    Which method is used to define an action that runs when a C# Task completes?

    1. AddAfter()
    2. RunLater()
    3. Chain()
    4. ContinueWith()

    Explanation: ContinueWith() is used to specify an action that should run after a Task has finished. RunLater, Chain, and AddAfter do not exist in task programming in C#. Continuations allow workflows to be chained cleanly after asynchronous operations.