Checkbox1.GetAttribute(“checked”) occur an Error: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED));

I am working on Windows form WebBrowser- Control.When I am accessing checkbox GetAttribute() method it gave me access denied error, below is the line of code :

if(Checkbox1!=null){if(Checkbox1.GetAttribute("checked")=="True")**//Here Error Comes.**{//Do Something }}

ERROR MESSAGE: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED));

Any suggestion.