dim Webview1 as Webview
Dim html = $"<!DOCTYPE html>
<html>"
<body onload='document.frm1.submit()'>
<form action='yoururl' method='post' name='frm1'>
<input Type='hidden' name='param1' value='v1><br>
<input Type='hidden' name='param2' value='v2><br>
<input Type='hidden' name='param3' value='v3><br>
</form>
</body>
</html>"$
WebView1.LoadHtml(html)