C#: async void vs async Task — why does my exception crash the app?

Question

An exception thrown in an `async void` method crashes my whole process instead of being caught by the caller's try/catch. Why?

Accepted Answer

An `async void` method returns **nothing the caller can await**, so the caller can't observe its exceptions. They're raised directly on the `SynchronizationContext` (or the thread pool), which usually crashes the process.

```csharp
// ❌
async void SaveAsync() { await db.SaveChangesAsync(); }

// ✅
async Task SaveAsync() { await db.SaveChangesAsync(); }
```

Rules:
- Always return `Task` or `Task<T>` (or `ValueTask`).
- The **only** legitimate `async void` is an event handler (`button.Click += async (s, e) => ...`). Wrap its body in try/catch.
- Enable the analyzer `VSTHRD100` (Microsoft.VisualStudio.Threading.Analyzers) to flag it.

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