How to load the URI programmatically in asp.net c# without redirection to another page

Question

I'm opening the url link to another page and getting the url querystring link, it is opening fine but in my programming scenario it should not redirect to another page it should red in the programmatically and should give that redirected url link.

I'm fresher and learning programing ....

this is how I did :-

On page load :-

  string srvscope = $"https://accounts.zoho.in/oauth/v2/auth?scope={scope}&client_id={Clientid}&state=ScopeGeneration&response_type=code&redirect_uri={redirect_uri}&access_type=offline";
             string Fullurl = srvscope;

OpenNewBrowserWindow(Fullurl, this);

Method :-

        public void OpenNewBrowserWindow(string Url, Control control)
        {
            //ScriptManager.RegisterStartupScript(control, control.GetType(), "Open", "window.open('" + Url + "');", true);

            ScriptManager.RegisterStartupScript(control, control.GetType(), "Open", "window.onload('" + Url + "');", true);
        }

Give me the best suggestion to achieve this .