已通过await等待的Task其IsCompleted属性是否可能返回false？

Short answer: Absolutely not — once you've awaited a Task, it is guaranteed to be in a completed state, so task.IsCompleted will always return true at that point.

Let me break this down for you:

How await works #

When you await a Task, the runtime will pause execution of the current method until the task reaches one of its final states: RanToCompletion, Faulted, or Canceled. It doesn't matter if the task completes synchronously (right when you call DoSomethingAsync) or asynchronously later — the await keyword ensures your code doesn't proceed past that line until the task is done.

What this means for your code #

Your original code:

Task task = DoSomethingAsync( someObject );
await task.ConfigureAwait( false );
if ( task.IsCompleted ){ ... }

That if check is completely redundant. After await task.ConfigureAwait(false);, task is guaranteed to be completed, so the condition will always evaluate to true.

Safe code replacement #

You can absolutely replace this with:

await DoSomethingAsync( someObject ).ConfigureAwait( false );

And remove the if statement entirely. This code behaves exactly the same as your original, but is cleaner and avoids unnecessary checks.

Confirming with the IsCompleted documentation #

As you noted, the docs state:

如果任务已完成（即任务处于RanToCompletion、Faulted或Canceled这三种最终状态之一），则返回true；否则返回false。

Since await only proceeds when the task is in one of these three final states, IsCompleted can't be false after awaiting. There's no scenario where this could happen — it's a fundamental guarantee of how async/await works in .NET.

内容的提问来源于stack exchange，提问作者Mong Zhu