Async Functions of Entity Framework not running properly

Question

As I know, asynchronous functions return immediately. The sample code below confirms me.

static void Main(string[] args) 
{
    StartTasks2();
    Console.ReadKey();
}

private static void StartTasks2() 
{
    Console.WriteLine($"Task2 Started: {DateTime.Now:s.ffff}");
    AddPersonFake();
    Console.WriteLine($"Task2 Finished: {DateTime.Now:s.ffff}");
}

private static async void AddPersonFake() 
{
    Console.WriteLine($"AddPersonFake Started: {DateTime.Now:s.ffff}");
    await Task.Delay(2000);
    Console.WriteLine($"AddPersonFake Finished: {DateTime.Now:s.ffff}");
}

But this code is not working (I'm waiting for the result as above):

static void Main(string[] args) 
{
    StartTasks1();
    Console.ReadKey();
}

private static void StartTasks1() 
{
    Console.WriteLine($"Task1 Started: {DateTime.Now:s.ffff}");
    AddPerson();
    Console.WriteLine($"Task1 Finished: {DateTime.Now:s.ffff}");
}

private static async void AddPerson() 
{
    Console.WriteLine($"AddPerson Started: {DateTime.Now:s.ffff}");

    using ( TempDbContext context = new TempDbContext() ) 
    {
        context.Persons.Add(new Person());
        await context.SaveChangesAsync();
    }

    Console.WriteLine($"AddPerson Finished: {DateTime.Now:s.ffff}");
}

How can I return immediately from AddPerson()?

Tomas Chabada · Accepted Answer · 2020-05-22 09:48:03Z

2

From what I learned here on StackOverflow yestarday, you can do it using:

private static async void AddPerson() {
    await Task.Yield();
    Console.WriteLine($"AddPerson Started: {DateTime.Now:s.ffff}");
    using ( TempDbContext context = new TempDbContext() ) {
        context.Persons.Add(new Person());
        await context.SaveChangesAsync();
    }
    Console.WriteLine($"AddPerson Finished: {DateTime.Now:s.ffff}");
}

Task.Yield() will start incompeleted Task and when awaiting it, that is the place where your asynchronous code will start.

In your original code, method AddPerson is running synchronously until it reaches the first await

edited May 22, 2020 at 9:48

answered May 22, 2020 at 9:41

Tomas Chabada

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