What is the difference between Task.WhenAll and Task.WhenAny in C#?

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**WhenAll** — waits for all. **WhenAny** — waits for first. **Task.WhenAll:** - Waits for all tasks to complete. - Returns array of results. ```csharp Task task1 = Task.Delay(1000).ContinueWith(_ => 1); Task task2 = Task.Delay(2000).ContinueWith(_ => 2); Task task3 = Task.Delay(500).ContinueWith(_ => 3); // Wait for all int[] results = await Task.WhenAll(task1, task2, task3); // results: [1, 2, 3] ``` **Task.WhenAny:** - Waits for first completed task. - Returns completed task. ```csharp Task task1 = GetFromServer1Async(); Task task2 = GetFromServer2Async(); Task task3 = GetFromServer3Async(); // Get fastest response Task fastest = await Task.WhenAny(task1, task2, task3); string result = await fastest; ``` **Use cases:** - **WhenAll** — parallel operations, need all results. - **WhenAny** — race condition, fastest wins.

C#: What is the difference between Task.WhenAll and Task.WhenAny in C#?