CODEWITHSUNDEEP
c#asynchronouslambda
core
core

Reputation: 33079

async lambda not awaiting

I have an extension method called Use that takes an Action as an argument:

IEnumerable<User> users;

service.Use(client => {
    users = client.GetUsers();
});

// users has a value now

When I go to use the async version of GetUsers():

IEnumerable<User> users;

service.Use(async (client) => {
    users = await client.GetUsersAsync();
});

// users is null

...then the line // users is null is reached before await client.GetUsersAsync() returns a result.

How do I make sure that if my Action's body includes any await keyword, execution doesn't continue past Use() before the await in the Action's body is finished?

Note that I can't change the signature of Use(). The Action argument cannot be changed to a Func.

Upvotes: 0

Views: 506

Answers (1)

Damir Arh
Damir Arh

Reputation: 17855

You will need to change the signature of Use if you want the async lambda to be awaited:

Task Use(Func<Task> action)
{
  await action();
}

and then await it:

await service.Use(async (client) => {
  users = await client.GetUsersAsync();
});

If you can't do that, your only option is to wait for the task to complete instead of awaiting it (which defeats the purpose of using the async method in the first place):

service.Use((client) => {
  users = client.GetUsersAsync().Result;
});

Upvotes: 1

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