C# how to work with list of task

Question

C# how to work with list of task

Dani_hnr 1

Hello guys
I'm trying to work with a list of tasks but the problem is I can't get a list of run tasks
how can I get the list of run tasks without list<>?

AgaveJoe 30,126 Reputation points

2021-10-02T15:59:55.287+00:00

Can you clarify the question or provide sample code that illustrates the problem you are trying to solve?
Dani_hnr 1 Reputation point

2021-10-02T16:29:18.6+00:00

for example, i have a list that name is ids
and have 10 field
and I want to turn of id 5
how can I do that
my code :
class Program
{
static void Main(string[] args)
{
foreach (var id in ids)
{
RunAsync(id);
}
}
public async Task RunAsync(int id)
{
while (true)
{
Console.WriteLine($"run {id}");
}
}
}
P a u l 10,761 Reputation points

2021-10-02T16:42:20.03+00:00
The first issue that I can spot is that RunAsync is actually synchronous (i.e. it uses neither the await keyword, or return a Task.) If you want your loop to be run inside a task you can use Task.Run to wrap your loop. Once you're returning a Task to the Main method, it will be able to await it.

The second issue is that your Main method doesn't await the response, so the program will exit potentially before your loops even begin. Your RunAsync also needs to be static, as it's being called by your Main method, which is static and static methods can't call instance methods.

If you make RunAsync static though you'll now have a new issue, which is that your first id will block the loop from iterating, so you'll just see a stream of your first ids being printed down the page. The way around this (now that RunAsync returns a Task) is to add all the response tasks to a collection, then use Task.WhenAll on the collection, which will keep all of your tasks running until completion (which is your case is indefinitely.)

Here's something to get you started:

class Program { static async Task Main(string[] args) { int[] ids = new[] { 1, 2, 3 }; List<Task> tasks = new List<Task>(); foreach (var id in ids) { tasks.Add(RunAsync(id)); } await Task.WhenAll(tasks); } public static Task RunAsync(int id) { return Task.Run(() => { while (true) { Console.WriteLine($"run {id}"); } }); } }

Dani_hnr 1

you didn't get what I mean let me give another example :`

namespace Bot
{
    class Program
    {
        static void Main(string[] args)
        {

             using (var ctx = new LuckyDuckDbContext())
                   {
                       foreach (var bot in ctx.Bots.ToList())
                            {
                                MainAsync(bot.Token);
                            }
                   }
         }
        public static async Task MainAsync(string token)
        {
            var discord = new DiscordClient(new DiscordConfiguration()
            {
                Token = token,
                TokenType = TokenType.Bot,
                Intents = DiscordIntents.AllUnprivileged
            });
            await discord.ConnectAsync();
            await Task.Delay(-1);
        }
     }
}

now if I want stop one of them
what should I do

P a u l 10,761 Reputation points

2021-10-02T18:28:51.733+00:00

You'll want to create a CancellationTokenSource, which you'll use to both stop your Task.Delay(-1) and also call DisconnectAsync on your discord client. You'll want to create this inside of Main and pass it into your MainAsync.

Here's an example of how you'd create/use a token:
https://learn.microsoft.com/en-us/dotnet/standard/parallel-programming/task-cancellation

Task.Delay has a constructor that accepts a CancellationToken, which is where you'll want to pass your CancellationTokenSource.Token to:
https://learn.microsoft.com/en-us/dotnet/api/system.threading.tasks.task.delay?view=net-5.0#System_Threading_Tasks_Task_Delay_System_Int32_System_Threading_CancellationToken_

Inside your MainAsync method you'll want to register a callback on your CancellationToken by calling Register on it, which you'll pass an action to, and that is where you'll want to call discord.DisconnectAsync():
https://learn.microsoft.com/en-us/dotnet/api/system.threading.cancellationtoken?view=net-5.0#methods

Once this is setup you should be able to just call .Cancel() on your CancellationTokenSource and that'll stop both your Task.Delay and disconnect your Discord client.

Your answer

AgaveJoe 30,126 Reputation points

2021-10-02T15:59:55.287+00:00

Can you clarify the question or provide sample code that illustrates the problem you are trying to solve?
Dani_hnr 1 Reputation point

2021-10-02T16:29:18.6+00:00

for example, i have a list that name is ids
and have 10 field
and I want to turn of id 5
how can I do that
my code :
class Program
{
static void Main(string[] args)
{
foreach (var id in ids)
{
RunAsync(id);
}
}
public async Task RunAsync(int id)
{
while (true)
{
Console.WriteLine($"run {id}");
}
}
}
P a u l 10,761 Reputation points

2021-10-02T16:42:20.03+00:00

The first issue that I can spot is that RunAsync is actually synchronous (i.e. it uses neither the await keyword, or return a Task.) If you want your loop to be run inside a task you can use Task.Run to wrap your loop. Once you're returning a Task to the Main method, it will be able to await it.

The second issue is that your Main method doesn't await the response, so the program will exit potentially before your loops even begin. Your RunAsync also needs to be static, as it's being called by your Main method, which is static and static methods can't call instance methods.

If you make RunAsync static though you'll now have a new issue, which is that your first id will block the loop from iterating, so you'll just see a stream of your first ids being printed down the page. The way around this (now that RunAsync returns a Task) is to add all the response tasks to a collection, then use Task.WhenAll on the collection, which will keep all of your tasks running until completion (which is your case is indefinitely.)

Here's something to get you started:

class Program { static async Task Main(string[] args) { int[] ids = new[] { 1, 2, 3 }; List<Task> tasks = new List<Task>(); foreach (var id in ids) { tasks.Add(RunAsync(id)); } await Task.WhenAll(tasks); } public static Task RunAsync(int id) { return Task.Run(() => { while (true) { Console.WriteLine($"run {id}"); } }); } }
Dani_hnr 1 Reputation point

2021-10-02T17:23:32.07+00:00

you didn't get what I mean let me give another example :`

namespace Bot { class Program { static void Main(string[] args) { using (var ctx = new LuckyDuckDbContext()) { foreach (var bot in ctx.Bots.ToList()) { MainAsync(bot.Token); } } } public static async Task MainAsync(string token) { var discord = new DiscordClient(new DiscordConfiguration() { Token = token, TokenType = TokenType.Bot, Intents = DiscordIntents.AllUnprivileged }); await discord.ConnectAsync(); await Task.Delay(-1); } } }

now if I want stop one of them
what should I do
P a u l 10,761 Reputation points

2021-10-02T18:28:51.733+00:00

You'll want to create a CancellationTokenSource, which you'll use to both stop your Task.Delay(-1) and also call DisconnectAsync on your discord client. You'll want to create this inside of Main and pass it into your MainAsync.

Here's an example of how you'd create/use a token:
https://learn.microsoft.com/en-us/dotnet/standard/parallel-programming/task-cancellation

Task.Delay has a constructor that accepts a CancellationToken, which is where you'll want to pass your CancellationTokenSource.Token to:
https://learn.microsoft.com/en-us/dotnet/api/system.threading.tasks.task.delay?view=net-5.0#System_Threading_Tasks_Task_Delay_System_Int32_System_Threading_CancellationToken_

Inside your MainAsync method you'll want to register a callback on your CancellationToken by calling Register on it, which you'll pass an action to, and that is where you'll want to call discord.DisconnectAsync():
https://learn.microsoft.com/en-us/dotnet/api/system.threading.cancellationtoken?view=net-5.0#methods

Once this is setup you should be able to just call .Cancel() on your CancellationTokenSource and that'll stop both your Task.Delay and disconnect your Discord client.

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C# how to work with list of task

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