public async Task LunchPaymentPage(HttpContext httpContext, string authorizationUrl) { Microsoft.AspNetCore.Http.HttpResponse response = httpContext.Response; response.Clear(); StringBuilder form = new StringBuilder(); form.Append("<html>"); form.AppendFormat("<body onload='document.forms[0].submit()'>"); form.AppendFormat("<form action='{0}' method='post'>", authorizationUrl); form.Append("</form>"); form.Append("</body>"); form.Append("</html>"); HasLunchedPaymentPage = true; await response.WriteAsync(form.ToString()); //response.Write(form.ToString()); //response.End(); }