Exception handling in async code in C Sharp (C#) - Mini Project: Build & Apply

Exception handling in async code

📖 Scenario: You are building a simple program that fetches data asynchronously. Sometimes, the fetch might fail, and you want to handle those errors gracefully.

🎯 Goal: Learn how to handle exceptions in asynchronous methods using try-catch blocks in C#.

📋 What You'll Learn

Create an async method that simulates data fetching

Add a boolean variable to control if the fetch should fail

Use a try-catch block to handle exceptions in the async method call

Print the result or error message

💡 Why This Matters

🌍 Real World

Handling errors in asynchronous operations is important in real-world apps like web requests, file access, or database calls to keep the app stable.

💼 Career

Knowing how to catch and handle exceptions in async code is a key skill for C# developers working on modern applications that use asynchronous programming.

1

Create an async method to fetch data

Write an async method called FetchDataAsync that returns a Task<string>. Inside, use await Task.Delay(500) to simulate waiting, then return the string "Data fetched successfully".

C Sharp (C#)

// Your code here

Need a hint?

Use async Task<string> as the method signature and await Task.Delay(500) to simulate delay.

2

Add a boolean to control failure

Add a public static boolean variable called shouldFail in the Program class and set it to false. Modify FetchDataAsync to throw an Exception with message "Fetch failed" if shouldFail is true.

C Sharp (C#)

using System.Threading.Tasks;

class Program
{
    // Add the boolean variable here

    public static async Task FetchDataAsync()
    {
        await Task.Delay(500);
        // Throw exception if shouldFail is true
        return "Data fetched successfully";
    }
}

Need a hint?

Use if (shouldFail) to check the boolean and throw new Exception("Fetch failed") to raise an error.

3

Use try-catch to handle exceptions

In the Main method, call FetchDataAsync inside a try block and await its result. Use a catch (Exception ex) block to catch exceptions. Store the result or the exception message in a string variable called output.

C Sharp (C#)

using System;
using System.Threading.Tasks;

class Program
{
    public static bool shouldFail = false;

    public static async Task FetchDataAsync()
    {
        await Task.Delay(500);
        if (shouldFail)
        {
            throw new Exception("Fetch failed");
        }
        return "Data fetched successfully";
    }

    public static async Task Main()
    {
        // Use try-catch and call FetchDataAsync
    }
}

Need a hint?

Use try and catch (Exception ex) to handle errors. Assign the awaited call result or exception message to output.

4

Print the output

Add a line in the Main method to print the output variable using Console.WriteLine(output).

C Sharp (C#)

using System;
using System.Threading.Tasks;

class Program
{
    public static bool shouldFail = false;

    public static async Task FetchDataAsync()
    {
        await Task.Delay(500);
        if (shouldFail)
        {
            throw new Exception("Fetch failed");
        }
        return "Data fetched successfully";
    }

    public static async Task Main()
    {
        string output;
        try
        {
            output = await FetchDataAsync();
        }
        catch (Exception ex)
        {
            output = ex.Message;
        }
        // Print the output
    }
}

Need a hint?

Use Console.WriteLine(output) to show the result or error message.