CODEWITHSUNDEEP
c#.netforeach
Roman Ratskey
Roman Ratskey

Reputation: 5259

Await Inside Foreach Keyword

I have a List of Task<bool> that i want to iterate it and depending on the awaited result i decide whether to continue or break but ironically the foreach just executes the tasks and await keyword does not work

Here is my code

private async void Execute(object sender, EventArgs e)
{
    var tList = new List<Task<bool>> { Method1(), Method2()};

    foreach (var task in tList)
    {
        var result = await task;

        if(!result)
            break;
    }
}

public async Task<bool> Method1()
{
    await Task.Delay(1000);
    Console.WriteLine("Method1");
    return false;
}

public async Task<bool> Method2()
{
    await Task.Delay(1000);
    Console.WriteLine("Method2");
    return true;
}

Result : Both functions are execute.

Question : How could i use await inside foreach ?.

And thanks in advance.

Upvotes: 6

Views: 6357

Answers (1)

Reed Copsey
Reed Copsey

Reputation: 564433

You can use await within a foreach exactly as you are doing now.

Result : Both functions are execute.

Both functions should execute. The result isn't set to false until Method2 returns, at which point both have already run. You're also starting both Task<bool> instances before you await either, so both are (potentially) running before your foreach loop.

Reverse the order of your methods, and they won't both necessarily run (though they may, as you're starting them):

var tList = new List<Task<bool>> { Method2(), Method1()};

If you want to delay this completely, you could write it as:

var tList = new List<Func<Task<bool>>> { Method2, Method1};

foreach (var taskFunc in tList)
{
    var result = await taskFunc();

    if(!result)
        break;
}

Upvotes: 10

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