Kuba's space

Kuba's space

Await tasks with multiple result types

Regularly I want to await a few tasks and get their result. Surprisingly, there is no obvious way to do that. Task.WhenAll can be helpful, as we see later, but it doesn't solve the problem.
My common scenario looks like this:

var dbTasks = getDataFromDbTasks();
var otherServiceTasks = GetDataFromServiceTasks();

var dbData = await dbTasks;
var otherServiceData = await otherServiceTasks;

I found this approach very verbose. I prefer to await all the tasks at the same time. That's why we have an extension method in our codebase specifically for this purpose:

public static class TaskAwaiter {
    public static async Task<ValueTuple<T1, T2>> AwaitAll<T1, T2>(
        Task<T1> x,
        Task<T2> y) 
            => (await x, await y);
}

Such AwaitAll method simplifies the above code to this:

var dbTask = getDataFromDbTask();
var otherServiceTask = GetDataFromServiceTask();
var (dbData, otherServiceData) = 
    await TaskAwaiter.AwaitAll(dbTask , otherServiceTask);

That's precisely what I wanted! So far, so good.

But there is one caveat. What if I have a lot of tasks to await? I don't want to add another extension with more and more parameters.

Here Task.WhenAll() method becomes handy. It creates a single task that completes when all the other supplied tasks have been completed.

Usage looks like follows:

var dbTask = getDataFromDbTask();
var singleTaskFromCollectionOfTasks = Task.WhenAll(CollectionOfTasks());

var (dbData, singleTaskData) = 
    await TaskAwaiter.AwaitAll(dbTasks, singleTaskFromCollectionOfTasks);

Armed with these two methods, I can quickly write meaningful and readable code.

 
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