Using 'async' in a console application in C# [duplicate]
This question already has answers here: Can't specify the 'async' modifier on the 'Main' method of a console app (18 answers) Closed 5 years ago.
I have this simple code:
public static async Task<int> SumTwoOperationsAsync()
{
var firstTask = GetOperationOneAsync();
var secondTask = GetOperationTwoAsync();
return await firstTask + await secondTask;
}
private async Task<int> GetOperationOneAsync()
{
await Task.Delay(500); // Just to simulate an operation taking time
return 10;
}
private async Task<int> GetOperationTwoAsync()
{
await Task.Delay(100); // Just to simulate an operation taking time
return 5;
}
Great. This compiles.
But let’s say I have a console application and I want to run the code above (calling SumTwoOperationsAsync()).
static void Main(string[] args)
{
SumTwoOperationsAsync();
}
But I've read that (when using sync) I have to sync all the way up and down:
Does this mean that my Main function should be marked as async?
Well, it can't be because there is a compilation error:
an entry point cannot be marked with the 'async' modifier
If I understand the async stuff , the thread will enter the Main function → SumTwoOperationsAsync → will call both functions and will be out. But until the SumTwoOperationsAsync
What am I missing?
In most project types, your async "up" and "down" will end at an async void event handler or returning a Task to your framework.
However, Console apps do not support this.
You can either just do a Wait on the returned task:
static void Main()
{
MainAsync().Wait();
// or, if you want to avoid exceptions being wrapped into AggregateException:
// MainAsync().GetAwaiter().GetResult();
}
static async Task MainAsync()
{
...
}
or you can use your own context like the one I wrote:
static void Main()
{
AsyncContext.Run(() => MainAsync());
}
static async Task MainAsync()
{
...
}
More information for async Console apps is on my blog.
Here is the simplest way to do this
static void Main(string[] args)
{
Task t = MainAsync(args);
t.Wait();
}
static async Task MainAsync(string[] args)
{
await ...
}
As a quick and very scoped solution:
Both Task.Result and Task.Wait won't allow to improving scalability when used with I/O, as they will cause the calling thread to stay blocked waiting for the I/O to end.
When you call .Result on an incomplete Task, the thread executing the method has to sit and wait for the task to complete, which blocks the thread from doing any other useful work in the meantime. This negates the benefit of the asynchronous nature of the task.
My solution. The JSONServer is a class I wrote for running an HttpListener server in a console window.
class Program
{
public static JSONServer srv = null;
static void Main(string[] args)
{
Console.WriteLine("NLPS Core Server");
srv = new JSONServer(100);
srv.Start();
InputLoopProcessor();
while(srv.IsRunning)
{
Thread.Sleep(250);
}
}
private static async Task InputLoopProcessor()
{
string line = "";
Console.WriteLine("Core NLPS Server: Started on port 8080. " + DateTime.Now);
while(line != "quit")
{
Console.Write(": ");
line = Console.ReadLine().ToLower();
Console.WriteLine(line);
if(line == "?" || line == "help")
{
Console.WriteLine("Core NLPS Server Help");
Console.WriteLine(" ? or help: Show this help.");
Console.WriteLine(" quit: Stop the server.");
}
}
srv.Stop();
Console.WriteLine("Core Processor done at " + DateTime.Now);
}
}
Follow WeChat
Success story sharing
Want to stay one step ahead of the latest teleworks?
Subscribe Now相似问题
- Should 'using' directives be inside or outside the namespace?
- How can I get the application's path in a .NET console application?
- How would I run an async Task<T> method synchronously?
- async/await - when to return a Task vs void?
- Using async/await for multiple tasks
- How and when to use ‘async’ and ‘await’
- Do you have to put Task.Run in a method to make it async?
- How do I handle async operations in Startup.Configure?
- Using async/await with a forEach loop
SumTwoOperationsAsync...right ? (assuming the Main calling method is not marked as async)asyncvia the "context".catch. If that's not what you're seeing, I recommend asking your own question with a minimal code example.