add double quotes to variable that came from array - powershell

Question

I'm creating a function that does some things to Excel files. The list of Excel files are passed into the function as an array called $excelFiles. The code shown below is in progress (it does not yet do all the things it's intended to do). This code, as written so far, appears to be failing because there are no quotes around the string held in $excelFile that sets the $wb variable (right before the nested foreach):
Function CovertExcelFileToTextFiles ($excelFiles)
{
# create an Excel application object (fire off Excel in the background)
$excelApp = New-Object -ComObject Excel.Application
$excelApp.Visible = $false
$excelApp.DisplayAlerts = $false
# get first 3 letters of each file's name
foreach ($excelFile in $excelFiles)
{
$name = Split-Path $excelFile.FullName -Leaf #get filename only from full path
$prefix = $name.Substring(0,3) #get first 3 letters of filename
#look at contents of this variable
$excelFile
$wb = $excelApp.Workbooks.Open($excelFile)
foreach ($ws in $wb.Worksheets)
{
$n = $prefix + "_"+ $ws.Name
$n
}
}
$excelApp.Quit()
}
Here is the error that appears in the console:
The reason I suspect the problem is lack of quotes is because the code works if $wb is set to a hardcoded file path.
I'm having difficulty figuring out how to get double quotes around the variable to feed into the line that sets $wb. I have tried "$excelFile" and the editor puts a red squiggly line under it so apparently that's not allowed. I have also tried creating a new variable and populating that with "$excelFile", then plugging that into the parenthesis in the $wb line. That causes an error in the console as well. How can double quotes be put around $excelFile?

Answer 1

Lack of quotes is not your issue. When you hardcode a file and use quotes, the quotes tell the parser that it's a string; they aren't part of the string value.
You need to know what data type $excelFile is (that is, $excelFiles is an array of what?).
If your use of $excelFile.FullName is correct, then it seems you're dealing with an object.
In that case, the .Open() method is likely expecting a [String] and won't understand the object you're passing it, so try:
$wb = $excelApp.Workbooks.Open($excelFile.FullName)
A good way to troubleshoot this kind of thing is to use PowerShell ISE, then set a breakpoint.
In your case, set a breakpoint on the $wb = ... line, execute, and when the breakpoint is hit, execution will stop at that line (before executing it).
At that point, you can use the console to execute statements that will be run in the context of your running code. So for example you could run:
$excelFile.GetType()
or
$excelFile | Get-Member
and learn some things about the object you're dealing with. You could look at its properties, etc.:
$excelFile.FullName
You can look at the overloads of the method you're calling:
$excelApp.Workbooks.Open # <-- note no parentheses