All 20 Asynchronous Programming questions
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C# › Asynchronous Programming

How do you run multiple asynchronous operations concurrently and wait for all of them using Task.WhenAll?

Intermediate

Answer

Start each async operation WITHOUT awaiting immediately (collecting the resulting Task objects), then await Task.WhenAll(tasks) once — this runs all operations CONCURRENTLY rather than sequentially, since each one begins executing the moment it's called, not when it's awaited.
Task<string> task1 = FetchUserAsync(1);
Task<string> task2 = FetchUserAsync(2);
Task<string> task3 = FetchUserAsync(3);
string[] results = await Task.WhenAll(task1, task2, task3); // all three run concurrently
Real-world example Fetching data for three independent API calls simultaneously instead of sequentially awaiting each one, cutting total wait time significantly.

Common follow-ups: How does Task.WhenAll handle it if ONE of the tasks throws an exception while others are still running?

Exception Handling
All 20 Asynchronous Programming questions