Get-ChildItem - Include from array not returning files

Config value: 

<FileTypesToDelete>*.txt,*.log,*.mf</FileTypesToDelete>

setting variable in script

[string[]]$FileTypesToDelete = @($configfile.Settings.FileTypesToDelete)
#$FileTypesToDelete =$configfile.Settings.FileTypesToDelete

i've tried both the above ways to set the $FileTypesToDelete var and the code where I'm using this:

$logFiles = Get-Childitem $dir"\*" -Include $FileTypesToDelete,$liveSiteLogs -Exclude $configfile.Settings.FileExclusions | Where {$_.LastWriteTime -le "$LastWrite"}

when I run this logic i get this error:

Get-ChildItem : Cannot convert 'System.String[]' to the type 'System.String' required by parameter 'Include'. Specified method is not supported.
At C:\Users\pmcma\Documents\Projects\Replace FileCleaner with PowerShell Script\TestSnippets.ps1:53 char:45+ $logFiles = Get-Childitem $dir"\*" -Include $FileTypesToDelete,$liveSiteLogs -Ex ...+                                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+ CategoryInfo          : InvalidArgument: (:) [Get-ChildItem], ParameterBindingException+ FullyQualifiedErrorId : CannotConvertArgument,Microsoft.PowerShell.Commands.GetChildItemCommand

but if I change this around and hard-code the values to be delete the code works fine:

$logFiles = Get-Childitem $dir"\*" -Include "*.txt","*.log",".mf", $liveSiteLogs -Exclude $fileExclusions | Where {$_.LastWriteTime -le "$LastWrite"}

but I want to read these values in from a config file so can anyone enlighten me as to why my top array is failing?

Thanks in advance