C# async task and async void diference

[akadmin]

The key difference between async Task and async void in C# lies in how they behave, how errors are handled, and when each should be used.

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Summary Table

Feature	async Task	async void
Return type	Returns a Task (can await)	Returns nothing (void)
Can be awaited	Yes	No
Exception handling	Caught by try/catch when awaited	Uncaught exceptions crash app
Use case	Regular async methods	Event handlers only
Testable / chainable	Can be awaited/tested	Not test-friendly

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Example: async Task

public async Task DoSomethingAsync()
{
    await Task.Delay(1000);
    Console.WriteLine("Done");
}

// Usage
await DoSomethingAsync();  // Can be awaited

• You can await it.
• Exceptions can be caught with try/catch.

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Example: async void

public async void DoSomething()
{
    await Task.Delay(1000);
    Console.WriteLine("Done");
}

// Usage
DoSomething(); // Cannot be awaited

• Can’t await it.
• If an exception occurs, it will bypass try/catch and potentially crash the application.
• Only appropriate for event handlers like:

button.Click += async (sender, e) => {
    await Task.Delay(1000);
    Console.WriteLine("Clicked");
};

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Rule of Thumb

Use async Task for almost everything.
Use async void only for event handlers.

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Let’s go through real-world examples to show the difference between async Task and async void, especially around exception handling and event handlers.

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async Task Example with Exception Handling

public async Task LoadDataAsync()
{
    await Task.Delay(500); // Simulate work
    throw new InvalidOperationException("Something went wrong");
}

// Caller method
public async Task RunAsync()
{
    try
    {
        await LoadDataAsync(); // Can await
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Caught: {ex.Message}"); // Will catch the exception
    }
}

Output:

Caught: Something went wrong

Safe and testable.
Exception is caught in try/catch because we awaited the Task.

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async void Example with Exception Handling (Fails)

public async void LoadData()
{
    await Task.Delay(500);
    throw new InvalidOperationException("Oops!");
}

public void Run()
{
    try
    {
        LoadData(); // No await here
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Caught: {ex.Message}"); // This will NOT run
    }
}

Output:

• The app crashes or logs an unhandled exception.

Why?
You can’t await void, so the method continues without waiting — and exceptions escape the try/catch.

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async void for UI Event Handler (Valid Use Case)

private async void Button_Click(object sender, EventArgs e)
{
    await Task.Delay(500);
    MessageBox.Show("Button clicked!");
}

This is OK:

• Events require void return type.
• async void is the only choice.
• Exceptions still need special handling (e.g. try/catch inside the method).

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Exception Handling Inside an async void Event Handler

private async void Button_Click(object sender, EventArgs e)
{
    try
    {
        await Task.Delay(500);
        throw new Exception("Button failed!");
    }
    catch (Exception ex)
    {
        MessageBox.Show($"Error: {ex.Message}");
    }
}

Best practice: Always use try/catch inside async void event handlers.

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TL;DR

Situation	Use
Regular async work	async Task
Want to await it later	async Task
Event handler (UI, events)	async void
Method throws exception	Avoid async void unless it’s an event

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