I have been working on a script that allows a user to select a csv file from their PC to be operated on, the code I have to get the CSV file is as follows

    #function to open a file selection dialouge at the $InitialDirectory, with filetype filter $FileTypeFilter and return the file name
    function Get-File($InitialDirectory, $FileTypeFilter) {  
        $OpenFileDialog = New-Object System.Windows.Forms.OpenFileDialog
        if ($initialDirectory) {
            $OpenFileDialog.initialDirectory = $initialDirectory
        }
        $OpenFileDialog.filter = $FileTypeFilter

        #setup modalform to allow the form object to always be on top
        $modalform = New-Object System.Windows.Forms.Form
        $modalform.TopMost = $true
    
        #open the dialouge box and ensure a file is selected
        if($NULL -ne $OpenFileDialog.ShowDialog($modalform).FileName){
            return $OpenFileDialog.FileName
        } 
        else {
            #if no file error and exit the script
            Throw "No File Selected!"
        }
    }

the issue I am seeing however is when the user selects a file, it fails the if statement and then throws the error. during debugging however I can see that the filename property of the $openfiledialog object is set to the appropriate filepath string

Image of variable tracking in Powershell Debugging

I have tried first opening the Dialog and then setting a variable = to the FileName as per below, however this leaves the variable blank with no contents and that too fails the check

    #function to open a file selection dialouge at the $InitialDirectory, with filetype filter $FileTypeFilter and return the file name
    function Get-File($InitialDirectory, $FileTypeFilter) {  
        $OpenFileDialog = New-Object System.Windows.Forms.OpenFileDialog
        if ($initialDirectory) {
            $OpenFileDialog.initialDirectory = $initialDirectory
        }
        $OpenFileDialog.filter = $FileTypeFilter

        #setup modalform to allow the form object to always be on top
        $modalform = New-Object System.Windows.Forms.Form
        $modalform.TopMost = $true
    
    
        $OpenFileDialog.ShowDialog($modalform)
        $file = $OpenFileDialog.FileName
        #open the dialouge box and ensure a file is selected
        if($NULL -ne $File){
            return $OpenFileDialog.FileName
        } 
        else {
            #if no file error and exit the script
            Throw "No File Selected!"
        }
    }

any help much appreciated