vb.net - Exception 0x800A01B6 using getElementById after the first load -


i have created ribbon powerpoint visual studio xml ribbon. ribbon has button that, simplifying, this:

  • opens ie browser
  • search element (hiddenfield) in code id
  • get value of element
  • print value in actual slide

it works correctly first time click button of ribbon, throws exception 0x800a01b6 following times click button.

this code executed when click button:

dim otype type = type.gettypefromprogid("internetexplorer.application") if otype isnot nothing     dim ie shdocvw.internetexplorer     ie = nothing     ie = trycast(activator.createinstance(otype), shdocvw.internetexplorer)      if ie isnot nothing         dim oempty object = [string].empty         dim ourl object = targeturl         ie.addressbar = false         ie.menubar = false         ie.toolbar = 0         ie.visible = true         ie.height = 800         ie.width = 1100         ie.navigate(ourl, oempty, oempty, oempty, oempty)     end if      while (ie.busy or ie.readystate <> readystate.readystate_complete)         sleep(1000)         application.doevents()     loop          sleep(10000) ' 10 seconds testing purpose      dim str string = string.empty     dim hdnstring htmlinputelement = ie.document.getelementbyid("hdnstring")     str = hdnstring.value      dosomething(str)      ie.quit()     ie = nothing end if

this code of website opens (targeturl), code remains identical in every load , hidden value changes: 

<html> <body>     <form name="form1" id="form1">         <input type="hidden" name="hdnstring" id="hdnstring" value="get string" />     </form> </body> </html>

the second time (and following) execute function: ie opens, website loads, waits 10 seconds , error in line:

dim hdnstring htmlinputelement = ie.document.getelementbyid("hdnstring")

with exception 0x800a01b6 message.

the strange thing if click viewsource in ie contextual menu while 10 seconds delay (the ones testing purpose), works perfect every time click button; if don't, exception 0x800a01b6 appers.

any idea of i'm doing wrong?

error details image:

screenshoot

the type of document property resolved @ run-time, it's object until then. why calling methods in results in so-called late binding - not yet know if getelementbyid method exists or not, has determined run-time.

you error because document not of ihtmldocument3 type, document type includes getelementbyid method.

what can try casting document ihtmldocument3 interface. since inherits ihtmldocument , ihtmldocument2 can cast between them if document 1 of earlier types.

directcast(ie.document, ihtmldocument3).getelementbyid("hdnstring")

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