What is ConfigureAwait in C#?

Question

Accepted Answer

**ConfigureAwait** — controls where continuation runs.

```csharp
// Default — captures context
await Task.Delay(1000);
// Continues on original context (UI thread, ASP.NET context)

// ConfigureAwait(false) — no context capture
await Task.Delay(1000).ConfigureAwait(false);
// Continues on thread pool thread
```

**When to use ConfigureAwait(false):**
- Library code (don't need context).
- Improves performance.
- Prevents deadlocks.

**When NOT to use:**
- UI code (need UI thread).
- ASP.NET (need HttpContext).

**Example — library:**
```csharp
public async Task<string> GetDataAsync() {
    // Library — no context needed
    await Task.Delay(1000).ConfigureAwait(false);
    return "data";
}
```

**Deadlock prevention:**
```csharp
// Bad — can deadlock
var result = GetDataAsync().Result;

// Good — no deadlock
var result = await GetDataAsync().ConfigureAwait(false);
```

C#: What is ConfigureAwait in C#?