Task.Factory.StartNew with async lambda and Task.WaitAll

Question

I'm trying to use Task.WaitAll on a list of tasks. The thing is the tasks are an async lambda which breaks Tasks.WaitAll as it never waits.

Here is an example code block:

List<Task> tasks = new List<Task>(); tasks.Add(Task.Factory.StartNew(async () => {     using (dbContext = new DatabaseContext())     {         var records = await dbContext.Where(r => r.Id = 100).ToListAsync();         //do long cpu process here...     } } Task.WaitAll(tasks); //do more stuff here   

This doesn't wait because of the async lambda. So how am I supposed to await I/O operations in my lambda?

Answer 1

Task.Factory.StartNew doesn't recognise async delegates as there is no overload that accepts a function returning a Task.

This plus other reasons (see StartNew is dangerous) is why you should be using Task.Run here:

tasks.Add(Task.Run(async () => ...