Wait for AsyncMethod in C# Constructor

Question

Given: I've a class which manages user storage. Now when creating the class I want to ensure indexes which is a asynchronous method. Currently i just call wait, but i don't feel comfortable to it as I'm a little concerned about unexpected behaviors like hanging threads.

public MongoUserStorage(IMongoDatabase database)
{
    userCollection = database.GetCollection<MongoUser>("Users");
    roleCollection = database.GetCollection<MongoUserRole>("UserRoles");

    CreateIndexesAsync().Wait();
}

Question:

What is best way to handle this asynchous mehtod? (I want to be sure that the indexes are present after the class is instantiated)

Just do: CreateIndexesAsync().Wait();

or

var task = CreateIndexesAsync();
task.ConfigureAwait(false);
task.Wait();

Or any better solution ?

ConfigureAwait does nothing if used this way. As you may noticed, it returns TaskAwaitable that is supposed to be await-ed instead of the task. The task itself is unaffected. I think you are stuck with what you are doing currently (along with all the related risks). — Ivan Stoev
– Ivan Stoev, Commented Oct 17, 2015 at 10:32
"concerned about unexpected behaviors like hanging threads" I think you should understand the issue first. That allows you to conclude that this is safe. — usr
– usr, Commented Oct 17, 2015 at 14:16

usr · Accepted Answer · 2015-10-17 14:18:19Z

3

You are referring to the classic SynchronizationContext deadlock. As long as CreateIndexesAsync does not use a SynchronizationContext which is very unlikely this is completely safe.

Research what ConfigureAwait does and how to use it. Your current usage demonstrates that you don't really know enough. task.ConfigureAwait(false); is a no-op because it creates a new TaskAwaiter and throws it away.

answered Oct 17, 2015 at 14:18

usr

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