Powershell script errors first time but works on second attempt - powershell

Question

I have a powershell script that searches for xls files and converts them to xlsx. Every time I run it for the first time I will get the error
Unable to find type [Microsoft.Office.Interop.Excel.XlFileFormat].
At C:\Users\wpauling\Documents\Quarter Report Scripts\convert.ps1:2 char:18
+ ... xlFixedFormat = [Microsoft.Office.Interop.Excel.XlFileFormat]::xlOpen ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (Microsoft.Offic...el.XlFileFormat:TypeName) [], RuntimeException
+ FullyQualifiedErrorId : TypeNotFound
However the second time I run it everything works as expected, what is the problem I am going nuts. Here is my script
#Converts xls into xlsx
$xlFixedFormat = [Microsoft.Office.Interop.Excel.XlFileFormat]::xlOpenXMLWorkbook
write-host $xlFixedFormat
$excel = New-Object -ComObject excel.application
$excel.visible = $false
$folderpath = "C:\Users\user1\Documents\Q4"
$filetype ="*xls"
Get-ChildItem -Path $folderpath -Include $filetype -recurse |
ForEach-Object `
{
$path = ($_.fullname).substring(0, ($_.FullName).lastindexOf("."))
"Converting $path"
$workbook = $excel.workbooks.open($_.fullname)
$path += ".xlsx"
$workbook.saveas($path, $xlFixedFormat)
$workbook.close()
remove-item $_.fullname
}
$excel.Quit()
$excel = $null
[gc]::collect()
[gc]::WaitForPendingFinalizers()

Answer 1

Start the script with the line
Add-Type -AssemblyName Microsoft.Office.Interop.Excel
Hope that helps.
p.s. Much less descriptive of course, but you can also use the numeric enum value 51 for the variable and not use the Add-Type.
See: XlFileFormat enumeration