Facebook Comment Textbox, Pressing Enter Key

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C#

Facebook-API

i am making a desktop app with browser, which posts comment

the Enter button is required to be pressed to post the comment

right now i am using folowing code

txt = "how r u";
            string initial = "";
            HtmlDocument Document = (HtmlDocument)e.Argument;
            foreach (HtmlElement hform in Document.GetElementsByTagName("form"))
            {
                if (hform.GetAttribute("action") == "/ajax/ufi/modify.php")
                {
                    foreach (HtmlElement hbtnComment in hform.GetElementsByTagName("input"))
                    {
                        if (hbtnComment.GetAttribute("value") == "Comment")
                        {
                            hbtnComment.InvokeMember("click");
                            System.Threading.Thread.Sleep(1000);
                            Application.DoEvents();
                            break;
                        }
                    }

                    HtmlElement htxtArea = hform.GetElementsByTagName("textarea")[0];
                    initial = htxtArea.InnerText;
                    htxtArea.Focus();
                    System.Threading.Thread.Sleep(200);
                    Application.DoEvents();
                    htxtArea.InnerHtml = txt;// +"<input id=\"abc\" type=\"submit\">";
                    System.Threading.Thread.Sleep(200);
                    Application.DoEvents();
                    SendKeys.SendWait("{ENTER}");
                    System.Threading.Thread.Sleep(200);
                    Application.DoEvents();
}
}

the problem with this code is, that it using SendKeys function, which requires the application to remain in focus, if the application is minimized then this code doesnt work

so kindly anyone who can help me in telling how we can make the text area feel that Enter key has been pressed