Powershell：無法調用空值表達式的方法錯誤

Question

我想通過powershell登錄到網站。

這裏是PS碼

$username = "userhere" 
$password = "passhere" 
$ie = New-Object -com InternetExplorer.Application 
$ie.visible=$false 
$ie.navigate("http://www.desistream.tv/en/login.shtml") 
while($ie.ReadyState -ne 4) {start-sleep -m 100} 
$ie.document.getElementById("username").value= "$username" 
$ie.document.getElementById("pass").value = "$password" 
$ie.document.getElementById("loginform").submit() 
start-sleep 20 
$ie.Document.body | Out-File -FilePath c:\web.txt 

這是錯誤，當我運行腳本，我得到。

PS C:\Users\myname\Desktop> .\new.ps1 
You cannot call a method on a null-valued expression. 
At C:\Users\myname\Desktop\new.ps1:9 char:1 
+ $ie.document.getElementById("loginform").submit() 
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
    + CategoryInfo   : InvalidOperation: (:) [], RuntimeException 
    + FullyQualifiedErrorId : InvokeMethodOnNull 

PS C:\Users\myname\Desktop> http://www.desistream.tv/en/index.shtml 

Answer 1

頁面沒有ID爲「loginform」的元素。