How to wait for some task to finish in ASP:NET/C#

See more:

C#

ASP.NET

threads

TPL

Task

Await

, +

Protected void Page_Load(object sender, EventArgs e)
{
    XDocument response = ThirdPartyAPI.HttpRequest(someParams);

    if(response != null)
    {
       var node = response.Root.Elements("documents").Elements("document");
       string url = node.ElementAt(0).Element("url").Value;

       
        UploadFileToXYZSiteWithHttpRequest(token, parentID,url);
    }
}

My scenario as following:
My problem here is that the response variable is null when my project is running.
But when I am debugging and put a breakpoint before the response variable and wait for some few seconds, lets say 3 seconds, I get the response I am expecting.

It seems that I have to wait for some seconds before executing HttpRequest() function in order have a response.

I tried putting the Thread.Sleep(3000) method before the mentioned code line but now my second function (UploadFileToXYZSiteWithHttpRequest) its not doing its work.

Should I wait for something to finish (I don't know what, may be the page load, a thread that its in the background) for then to execute the ThirdPartyAPI.HttpRequest method?

should I use Threads or Task<tresult> class or anything else? if so, how to achieve this?

Please help me to clarify my way to solve this.
thanks.