Say I have a set of tasks:
var task1 = DoThisAsync(...);
var task2 = DoThatAsync(...);
var task3 = DoOtherAsync(...);
var taskN...
I am looking for a way to process a set of tasks in order (determined by place in containing collection say), but to have the tasks only run/start when its their turn and not before - and have all of that wrapped up in its own task.
Problem constraints / details are:
The main problem is that as soon as I call the relevant method (like DoThis()...) to return each task, that task is already 'hot' or running, violating (2) above.
I have tried working with.ContinueWith(..) , but if I call each of tasks like above to set the continuations or add them to a list or collection they've already started.
Not sure if Lazy < T > might help but can't see how at present?
Hope this makes sense as I'm fairly new to async / await / tasks.
Many thanks in advance.
Calling a method runs code. If you want an object that will call this method later , then use a delegate.
In this case, you could use Func<Task>
, which is an asynchronous delegate. A list of these should suffice:
// Build the list of operations in order.
var operations = new List<Func<Task>>();
operations.Add(() => DoThisAsync(...));
operations.Add(() => DoThatAsync(...));
operations.Add(() => DoOtherAsync(...));
// Execute them all one at a time.
foreach (var operation in operations)
await operation();
you can simply create tasks with its constructor and then, call execution with .Start() methods.
Here an example:
var taskList = InitQueue();
foreach (var t in taskList.OrderBy(i => i.Order))
{
//Here I can skedule an existing task
t.TaskToRun.Start();
t.TaskToRun.Wait();
Console.WriteLine($"Task {t.Order} has finished its job");
}
public class TaskQueue : List<TaskItem>
{
}
public class TaskItem
{
public int Order { get; set; }
public Task TaskToRun { get; set; }
}
private static TaskQueue InitQueue()
{
var queue = new TaskQueue();
queue.Add(new TaskItem
{
Order = 1,
TaskToRun = new Task(() =>
{
Task.Delay(500);
Console.WriteLine("Hello from task 1");
})
});
queue.Add(new TaskItem
{
Order = 4,
TaskToRun = new Task(() => Console.WriteLine("Hello from task 4"))
});
queue.Add(new TaskItem
{
Order = 3,
TaskToRun = new Task(() =>
{
Task.Delay(5000);
Console.WriteLine("Hello from task 3");
})
});
queue.Add(new TaskItem
{
Order = 2,
TaskToRun = new Task(() => Console.WriteLine("Hello from task 2"))
});
return queue;
}
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