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Visual Studio Code – Want to read the HTML markup of a webpage. What am I doing wrong here?

namespace WebReader
{
    public partial class frm_Main : Form
    {
        public frm_Main()
        {
            InitializeComponent();
        }

        private void frm_Main_Load(object sender, EventArgs e)
        {
            using var clt= new HttpClient();
            var res = clt.GetAsync("https://daera.net/dmoon/testfile.txt");

            while (true)
            {
                if (res.IsCompletedSuccessfully)
                {
                    var msg = clt.GetStringAsync("https://daera.net/dmoon/testfile.txt");
                    MessageBox.Show(msg.ToString());
                    break;
                }
            }
        }
    }
}

This code is supposed to show the contents of the text file https://daera.net/dmoon/testfile.txt, but it shows a message box with some technical information regarding clt object and nothing else.

What am I doing wrong? I am using Visual Studio 2019.

Tags:

2

Answers


  1. 0

    Oversimplifying, but you want to await the results of Async methods:

    using var clt= new HttpClient();
var res = await clt.GetAsync("https://daera.net/dmoon/testfile.txt");

    Do this, and you won’t need the while (true) loop.

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  2. 0

    As I said in the comments, the GetStringAsync() call is also asynchronous and returns a Task<String>.

    You have several options for synchronizing these tasks with your main program.

    1. The one you used: a while(true) loop checking for IsCompletedSuccessfully. This is not recommended at all, because it eats your resources doing nothing.
    2. Using Task.Wait(). This is a blocking call and what you’re looking for. (Edited: it’s closer to your original loop without eating resources; but you probably don’t want to block your form until the HTTP call ends, which would make your program unresponsive. Look for option 3 or Task.ContinueWith())
    3. Using await as in @Joel’s answer (*).

    This is your code, using option 1 for GetAsync() (again, not recommended) and option 2 for GetStringAsync().

    namespace WebReader
{
    public partial class Program
    {
        static void Main ()
        {
            using var clt= new HttpClient();
            var res = clt.GetAsync("https://daera.net/dmoon/testfile.txt");
            while (true)
            {
                if (res.IsCompletedSuccessfully)
                {
                    var responseTask = clt.GetStringAsync("https://daera.net/dmoon/testfile.txt");
                    responseTask.Wait();
                    Console.WriteLine(responseTask.Result.ToString());
                    break;
                }
                
            }
        }
    }
}

    (*) When you use await before an asynchronous function call, the current function (ie. the caller) won’t execute the instructions following the call until the asynchronous task completes; but it will immediately return to its own caller. That is, the caller will also be asynchronous (and that’s the reason for the mandatory async keyword).

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