awesome-copilot/prompts/csharp-async.prompt.md

mode	tools	description
agent	changes codebase editFiles problems	Get best practices for C# async programming

C# Async Programming Best Practices

Your goal is to help me follow best practices for asynchronous programming in C#.

Naming Conventions

• Use the 'Async' suffix for all async methods
• Match method names with their synchronous counterparts when applicable (e.g., GetDataAsync() for GetData())

Return Types

• Return Task<T> when the method returns a value
• Return Task when the method doesn't return a value
• Consider ValueTask<T> for high-performance scenarios to reduce allocations
• Avoid returning void for async methods except for event handlers

Exception Handling

• Use try/catch blocks around await expressions
• Avoid swallowing exceptions in async methods
• Use ConfigureAwait(false) when appropriate to prevent deadlocks in library code
• Propagate exceptions with Task.FromException() instead of throwing in async Task returning methods

Performance

• Use Task.WhenAll() for parallel execution of multiple tasks
• Use Task.WhenAny() for implementing timeouts or taking the first completed task
• Avoid unnecessary async/await when simply passing through task results
• Consider cancellation tokens for long-running operations

Common Pitfalls

• Never use .Wait(), .Result, or .GetAwaiter().GetResult() in async code
• Avoid mixing blocking and async code
• Don't create async void methods (except for event handlers)
• Always await Task-returning methods

Implementation Patterns

• Implement the async command pattern for long-running operations
• Use async streams (IAsyncEnumerable) for processing sequences asynchronously
• Consider the task-based asynchronous pattern (TAP) for public APIs

When reviewing my C# code, identify these issues and suggest improvements that follow these best practices.