Writing to the console using Task.Run() fails

Question

A colleague of mine found an issue with our code and it took a while to hunt down exactly what was happening, but it can be best demonstrated by this simple example:

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Answer 1

I have a suspicion as to what's going on. What I've observed:

• If you do anything with the console's output before starting the ReadKey, it's fine. This includes fetching Console.Out but not using it
• If you put a delay in so that the Console.WriteLine call starts before the Console.ReadKey call, it's fine (and you can have multiple WriteLine calls while ReadKey is waiting

I suspect that the first operation to use the console acquires a lock for initialization (to avoid it being initialized twice) and that the ReadKey method keeps hold of the lock until a key has been read. That would certainly explain every program I've run so far.

The operations which perform the hypothesized initialization are interesting though - reading Console.Out "fixes" the issue, but reading from Console.In doesn't.

I suspect that ReadKey initializes the output because the value is still echoed to the console... but I wouldn't like to swear to it.

Interestingly, using Console.ReadLine() instead of Console.ReadKey() doesn't cause the problem in the first place.

Answer 2

Actually, the first case doesn't fail. "Hello World" appears just before the Application ends. This is a classical Race Condition. In the first case,Console.ReadKey() from the main thread beats the task, and in the second case, the task wins. Unfortunately, I cannot tell you Exactly why writing the empty string makes the task win.