Question

I’m building a software to process orders on a site. I’m using DOM to navigate through the website and I want my app not to hang when I use a command on the “wrong” page.

Ex:

try
  WebBrowser.OleObject.Document.GetElementByID('ContentPlaceHolder1_txtCommande').setAttribute('value', lblDate.Caption);
except
end;

All I want is for the error to be ignored if the field is not found as this error is not important. Thank you!

Edit: wrote ADO when I meant DOM

Answer 1

You yourself say that the element might not be found, so what do you expect

WebBrowser.OleObject.Document.GetElementByID('ContentPlaceHolder1_txtCommande')

to return other than nil in that case? Yet you “blatantly” use whatever is returned by appending

.setAttribute('value', lblDate.Caption);

to it.

Change your code to

var
  element: IDomElement; // Whatever it should really be
begin
  element := WebBrowser.OleObject.Document.GetElementByID('ContentPlaceHolder1_txtCommande');
  if Assigned(element) then
    element.setAttribute('value', lblDate.Caption);

Edit

if you are working with variants instead of using msxml through its type library or some other xml library in which you can find the proper type returned by GetElementID, then, as @GerryColl mentions, you can use element: OLEVariant and check for NULL instead of for a nil pointer.