Returning values from async methods in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of async method returning Task

What is the output of this C# program when run?

C Sharp (C#)

using System;
using System.Threading.Tasks;

class Program {
    static async Task<int> GetNumberAsync() {
        await Task.Delay(100);
        return 42;
    }

    static async Task Main() {
        int result = await GetNumberAsync();
        Console.WriteLine(result);
    }
}

A 42

B Task`1

C 0

D Compilation error

💡 Hint

Remember that awaiting an async method unwraps the Task and gives the actual return value.

The method GetNumberAsync returns a Task. Awaiting it in Main unwraps the Task and returns the integer 42, which is printed.

❓ Predict Output

intermediate

Return type of async method without Task

What happens when you try to compile and run this code?

C Sharp (C#)

using System;
using System.Threading.Tasks;

class Program {
    static async Task<int> GetNumberAsync() {
        await Task.Delay(100);
        return 10;
    }

    static async Task Main() {
        int result = await GetNumberAsync();
        Console.WriteLine(result);
    }
}

A Compilation error

B Runtime exception

C Prints 10

D Prints Task`1

💡 Hint

Async methods must return Task, Task, or void (rarely).

Async methods cannot have return type int directly. They must return Task for async methods returning int values.

🔧 Debug

advanced

Why does this async method return null?

Consider this code snippet. Why does the output print "Result is: " with no number after it?

C Sharp (C#)

using System;
using System.Threading.Tasks;

class Program {
    static async Task<string> GetTextAsync() {
        await Task.Delay(50);
        string text = null;
        return text;
    }

    static async Task Main() {
        string result = await GetTextAsync();
        Console.WriteLine($"Result is: {result}");
    }
}

A The method throws an exception causing no output.

B The await is missing so result is null.

C The method returns null string, so nothing is printed after the colon.

D The Console.WriteLine is incorrect and does not print the variable.

💡 Hint

Check what value the async method returns and how null strings print.

The method returns a null string. When printing with interpolation, null prints as empty, so output is "Result is: " with nothing after.

❓ Predict Output

advanced

Output of async method returning Task without await

What is the output of this program?

C Sharp (C#)

using System;
using System.Threading.Tasks;

class Program {
    static async Task DoWorkAsync() {
        Console.WriteLine("Start");
        // No await here
        Console.WriteLine("End");
    }

    static async Task Main() {
        await DoWorkAsync();
    }
}

A Compilation error

B Start\nEnd

C End

D Start

💡 Hint

Async methods can run synchronously if no await is present.

Since DoWorkAsync has no await, it runs synchronously printing Start then End immediately.

🧠 Conceptual

expert

What is the type of the value returned by an async method with signature 'async Task'?

Given an async method declared as 'async Task ComputeAsync()', what is the type of the value you get when you await this method?

A void

B Task<int>

C Task

D int

💡 Hint

Await unwraps the Task and gives the inner value.

Awaiting a Task returns the int value inside the Task.