C# IAsyncDisposable — Complete Guide

In this tutorial, you'll learn about C# IAsyncDisposable. We cover key concepts, practical examples, and best practices.

Your class holds a network connection, a file handle, or a database connection that requires asynchronous cleanup. IDisposable is synchronous — it blocks the thread during disposal. IAsyncDisposable lets you clean up asynchronously without blocking.

Wrong

public class DbConnection : IDisposable
{
    public void Dispose()
    {
        _connection.CloseAsync().GetAwaiter().GetResult(); // Blocks thread
    }
}

Output: Dispose blocks the calling thread with .GetAwaiter().GetResult(). This can cause deadlocks in synchronization contexts.

Right

public class DbConnection : IAsyncDisposable
{
    public async ValueTask DisposeAsync()
    {
        await _connection.CloseAsync();
    }
}

// Usage
await using var conn = new DbConnection();
// ... use conn ...
// DisposeAsync is called automatically at the end

Output: Cleanup happens asynchronously. No thread blocking, no deadlocks.

IAsyncDisposable is the async counterpart of IDisposable. Use await using to consume it. The pattern also supports the dispose-before-rethrow semantics.

Prevention

• Implement IAsyncDisposable when cleanup involves async I/O (file close, network disconnect, DB connection close).
• Use await using to consume IAsyncDisposable resources.
• Implement both IDisposable and IAsyncDisposable when you need sync and async disposal paths.
• Use ValueTask as the return type for DisposeAsync — it is allocation-free when disposal completes synchronously.
• Call DisposeAsync from Dispose only as a fallback — prefer the async path.
• Use ConfigureAwait(false) in DisposeAsync when context is not needed.

Common Mistakes with async disposable

1. Misunderstanding that String is [Char] with poor performance for large text operations
2. Using foldl instead of foldl' causing stack overflow on large lists
3. Forgetting deriving (Show, Eq) on custom data types needed for debugging

These mistakes appear frequently in real-world CSHARP code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ

await using var tx = await db.BeginTransactionAsync();
try {
    // ... work ...
    await tx.CommitAsync();
} catch {
    await tx.DisposeAsync(); // Rollback on error
    throw;
}

IAsyncDisposable is used in DodaTech's database layer for proper async connection lifecycle management. For more, visit DodaTech.