Task and Task of T types in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Task that runs a method asynchronously.

C Sharp (C#)

Task myTask = Task.[1](() => Console.WriteLine("Hello from Task"));

Drag options to blanks, or click blank then click option'

AStart

BRun

CExecute

DBegin

Attempts:

3 left

💡 Hint

Common Mistakes

Using Task.Start directly on a delegate instead of creating a Task first.

Confusing Task.Run with Task.Factory.StartNew.

The Task.Run method is used to start a task that runs asynchronously.

2fill in blank

medium

Complete the code to create a Task that returns an integer result asynchronously.

C Sharp (C#)

Task<int> myTask = Task.[1](() => 42);

Drag options to blanks, or click blank then click option'

ARun

BStart

CExecute

DBegin

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to use Task.Start with a lambda directly.

Using Task.Factory.StartNew without specifying the return type.

Task.Run can be used with a lambda that returns a value, creating a Task<T>.

3fill in blank

hard

Fix the error in the code to await a Task that returns a string.

C Sharp (C#)

async Task<string> GetMessageAsync() {
    return await [1];
}

Task<string> messageTask = Task.FromResult("Hello");

Drag options to blanks, or click blank then click option'

AmessageTask.Result

BmessageTask.GetAwaiter()

CmessageTask

DmessageTask.Wait()

Attempts:

3 left

💡 Hint

Common Mistakes

Awaiting the Result property instead of the Task.

Calling Wait() which blocks instead of awaiting.

You should await the Task itself, not its Result property or Wait method.

4fill in blank

hard

Fill both blanks to create and start a Task that returns the length of a string.

C Sharp (C#)

Task<int> lengthTask = new Task<int>(() => [1].Length);
lengthTask.[2]();

Drag options to blanks, or click blank then click option'

AinputString

BStart

CRun

DExecute

Attempts:

3 left

💡 Hint

Common Mistakes

Using Task.Run instead of new Task and Start.

Forgetting to start the Task after creating it.

You create a Task with a lambda using inputString.Length and start it with Start().

5fill in blank

hard

Fill all three blanks to create a Task that returns the uppercase version of a string and start it.

C Sharp (C#)

Task<string> upperTask = new Task<string>(() => [1].[2]());
upperTask.[3]();

Drag options to blanks, or click blank then click option'

Ainput

BToUpper

CStart

DRun

Attempts:

3 left

💡 Hint

Common Mistakes

Using Task.Run instead of new Task and Start.

Calling the method without parentheses.

Not starting the Task.

The Task uses input.ToUpper() in the lambda and is started with Start().

Practice

1. What is the main difference between Task and Task<T> in C#?

easy

A. Task does not return a value, Task<T> returns a value of type T.

B. Task runs synchronously, Task<T> runs asynchronously.

C. Task is used only for UI threads, Task<T> for background threads.

D. Task can return multiple values, Task<T> returns only one.

Solution

1. Step 1: Understand Task behavior

   Task represents an asynchronous operation that does not return a result.

2. Step 2: Understand Task<T> behavior

   Task<T> represents an asynchronous operation that returns a value of type T when it completes.

3. Final Answer:

   Task does not return a value, Task<T> returns a value of type T. -> Option A

4. Quick Check:

   Return value presence = Task does not return a value, Task<T> returns a value of type T. [OK]

Hint: Remember: Task = no result, Task<T> = returns result [OK]

Common Mistakes:

• Thinking Task runs synchronously
• Confusing Task<T> with multiple return values
• Assuming Task is only for UI threads

2. Which of the following is the correct way to declare a Task<int> that returns the number 5 asynchronously?

easy

A. Task<int> t = Task.Run(() => 5);

B. Task<int> t = new Task<int>(5);

C. Task<int> t = Task<int>.Run(5);

D. Task<int> t = Task.Run<int>(5);

Solution

1. Step 1: Check correct Task<T> creation syntax

   Use Task.Run(() => value) to create and start a task returning a value.

2. Step 2: Validate each option

   Task<int> t = Task.Run(() => 5); uses Task.Run(() => 5), which is correct. Options A, B, and C use invalid constructors or methods.

3. Final Answer:

   Task<int> t = Task.Run(() => 5); -> Option A

4. Quick Check:

   Correct Task creation syntax = Task<int> t = Task.Run(() => 5); [OK]

Hint: Use Task.Run with lambda to return values asynchronously [OK]

Common Mistakes:

• Trying to pass value directly to Task constructor
• Using non-existent Task.Run overloads
• Confusing Task and Task<T> creation

3. What will be the output of this C# code?

async Task<int> GetNumberAsync() { return 10; }

var task = GetNumberAsync();
Console.WriteLine(task.Result);

medium

A. Task<int>

B. 10

C. Compilation error

D. Deadlock or runtime error

Solution

1. Step 1: Understand async method returning Task<int>

   The method returns a Task that completes with value 10.

2. Step 2: Accessing task.Result

   Accessing Result blocks until the task finishes and returns 10.

3. Final Answer:

   10 -> Option B

4. Quick Check:

   Task.Result blocks and returns value = 10 [OK]

Hint: Task.Result blocks and returns the result value [OK]

Common Mistakes:

• Expecting Task<int> printed instead of value
• Thinking async method returns int directly
• Assuming runtime error without synchronization context

4. Identify the error in this code snippet:

Task<int> task = Task.Run(() => 42);
int result = await task;

medium

A. Task<int> must be declared as void

B. Task.Run cannot return int

C. Cannot use await outside an async method

D. Missing parentheses in Task.Run

Solution

1. Step 1: Check usage of await keyword

   await can only be used inside methods marked with async.

2. Step 2: Analyze code context

   The snippet does not show an async method, so using await here causes a compile error.

3. Final Answer:

   Cannot use await outside an async method -> Option C

4. Quick Check:

   Await requires async method = Cannot use await outside an async method [OK]

Hint: Always mark method async to use await inside it [OK]

Common Mistakes:

• Assuming Task.Run cannot return int
• Thinking Task<int> can be void
• Ignoring async keyword requirement for await

5. You want to run two tasks in parallel: one returns an int, the other returns a string. How do you wait for both and get their results efficiently?

hard

A. Use Task.WaitAll(task1, task2) and cast results to correct types.

B. Call task1.Wait() and task2.Wait() sequentially, then get results.

C. Use await task1 then await task2 one after another.

D. Use await Task.WhenAll(task1, task2) then access task1.Result and task2.Result.

Solution

1. Step 1: Understand parallel task waiting

   Task.WhenAll waits for all tasks to complete concurrently.

2. Step 2: Access results after waiting

   After await Task.WhenAll(...), you can safely access each task's Result without blocking.

3. Final Answer:

   Use await Task.WhenAll(task1, task2) then access task1.Result and task2.Result. -> Option D

4. Quick Check:

   Parallel wait with Task.WhenAll = Use await Task.WhenAll(task1, task2) then access task1.Result and task2.Result. [OK]

Hint: Use Task.WhenAll to await multiple tasks efficiently [OK]

Common Mistakes:

• Waiting tasks sequentially losing parallelism
• Using blocking Wait() causing deadlocks
• Casting results instead of accessing Task<T>.Result