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Alvaro Fabian M
Asked: 2020-04-27 18:41:10 +0800 CST 2020-04-27 18:41:10 +0800 CST

What is the equivalent of a Java async task (AsinckTask<>) in C#?

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I am dedicated to developing for Android but now I am involved in a project that involves development for Desktop in C#

Some time ago I had created this class that extends the AsyncTask class, what this class does is do a GET to a url and return the result as a jsonString

blic class LectorJsonHttp extends AsyncTask<String, Void, String> {

private LectorJsonHttpResultado lectorJsonHttpResultado;
boolean lecturaCorrecta = false;

public LectorJsonHttp(LectorJsonHttpResultado lectorJsonHttpResultado) {
    this.lectorJsonHttpResultado=lectorJsonHttpResultado;


}
@Override
protected void onPreExecute() {
    super.onPreExecute();
}

@Override
    protected String doInBackground(String... httpUrl) {
    String jsonString="error";
    try {
        StrictMode.ThreadPolicy Policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(Policy);

        HttpClient objCliente = new DefaultHttpClient();
        HttpContext objContext = new BasicHttpContext();
        HttpGet objGet = new HttpGet(httpUrl[0]);

        HttpResponse objResponse = objCliente.execute(objGet, objContext);
        HttpEntity objEntidad = objResponse.getEntity();
        jsonString = EntityUtils.toString(objEntidad, "UTF-8");
        if(!jsonString.equals("error"))lecturaCorrecta = true;
    }catch (Exception E)
    {
        lecturaCorrecta = false;
    }

    return  jsonString;
    }

@Override
protected void onPostExecute(String jsonString) {

    lectorJsonHttpResultado.abstractMtdJsonString(jsonString,lecturaCorrecta);

    super.onPostExecute(jsonString);


}

Now in the c# project I need to do the same thing, I have researched for a long time but I don't find something really understandable since asynchronous tasks in C# don't have a postExecute method that can be used to send data to the main thread through an Interface, I hope that you can give me some advice or a clue to be able to do this, thanks in advance

java

1 Answers

  1. Best Answer

    For asynchronous programming there are several options in C#. You can use BackGroundWorkeror as you have already been told in a comment, Task. I would recommend the latter since it is more modern and powerful.

    For the case you expose, the only thing you need is to use HttpClientin an asynchronous method. Here is a very simple example of how to download a page using GetAsyncand Task:

    public static void Main(string[] args)
{
     DescargarJson();
}

static async void DescargarJson()
{
    var r = await Descargar("http://stackoverflow.com");
    Console.WriteLine(r);
}

static async Task<string> Descargar(string url)
{
    using(var client = new HttpClient())
    {
        using(var r = await client.GetAsync(new Uri(url)))
        {
            string result = await r.Content.ReadAsStringAsync();
            return result;
        }
    }
}
    • 4