Convert a string variable into an integer

I’m trying to convert my $file_data variable into an integer, the bit of code below grabs the number of a computer on my system held in a directory. However when run in PowerShell I get he below error even though the variable is a number.

The '++' operator works only on numbers. The operand is a 'System.String'.
At D:\pscript\Intune.ps1:7 char:26
+ For ($file_data -le 130; $file_data++ ){
+                          ~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : OperatorRequiresNumber

I’m not sure where I’m going wrong on this any help would be amazing. 🙂

Get-Content D:\pscript\temp\Directory.txt
$file_data = Get-Content D:\pscript\temp\Directory.txt

>Solution :

For converting string to integer, you can typecast it or declare it at the first point.

[int] $file_data = Get-Content D:\pscript\temp\Directory.txt

However, if this needs to work, Directory.txt should have number which can fit into the category of an integer.