c# - 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 () => ...