CODEWITHSUNDEEP
c#.netasync-awaitdotnet-httpclient
user3799149
user3799149

Reputation: 39

Call HttpClient.GetAsync in console application - Deadlock

I searched and saw many posts and I don't know why this simple console call using httpclient.getasync and awaiting it causes it not to complete. here is the code:

using System;
using System.Net.Http;
using System.Threading.Tasks;

public class Program
{
    public static void Main(string[] args)
    {
        GetAPI().Wait();
        Console.WriteLine("Hello");
        //Console.ReadLine();
    }

    public static async Task GetAPI()
    {
        using (HttpClient client = new HttpClient())
        {
            var response = await client.GetAsync("https://www.google.com/");
            //var response = client.GetAsync("https://www.google.com/").Result

            string content = await response.Content.ReadAsStringAsync();
            Console.WriteLine(content);
        }
    }
}

If I change to use client.GetAsync("https://www.google.com/").Result; and remove "await" (see commented out code) it will work however I believe that is a no no because I am making an asynchronous function into synchronous. I've seen other posts and blogs about this and it all claims what I am trying to do is correct but when running the example app it just doesn't turn out that way.

Upvotes: 3

Views: 6318

Answers (2)

Legends
Legends

Reputation: 22702

You can call wait() in Main.

But be carefull, this only works in console applications and will dead lock in UI applications like WPF, WinForms or in ASP.NET context...

public static void Main(string[] args)
{
    
    try
    {           
         var t =  GetAPI();
         t.Wait();
         Console.WriteLine(t.Result);   
    }
    catch (Exception ex)
    {
         Console.WriteLine(ex.Message);  
    }
      
}

public static async Task<string> GetAPI()
{
   using (HttpClient client = new HttpClient())
   {
      var response = await client.GetAsync("https://www.google.com/"); 
      string content = await response.Content.ReadAsStringAsync(); 
  
     return content;
   }
}

MSDN

This code will work just fine in a console application but will deadlock when called from a GUI or ASP.NET context.

Upvotes: 4

Devesh
Devesh

Reputation: 4550

The issue is that awaiting the client.GetAsync, after getting the result is waiting for main thread to be free and main thread is waiting for client.GetAsync to complete.

       var response = await client.GetAsync("https://www.google.com/").ConfigureAwait(false);
       string content = await response.Content.ReadAsStringAsync().ConfigureAwait(false);

Will tell that client.GetAsync to complete on other thread and then return the result back to main thread so that no more dead lock.

Upvotes: 1

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