Database information and drive space in one function

Question

Good day all,
I'm trying to come up with a function that I can run across all mailbox servers in my environment; gathering information such as drives presented to it, drive capacity, drive free space, database size, mbx count, avg mbx size, database whitespace, etc..
I start running into errors when I wanted to add the drive report to this. Can anyone take a look and see where im faulting? When I run this I get  "you cannot call a method on a null-valued expression.'
Thank you for your help.
function DatabaseStatistics{
$ExchangeServers = get-exchangeserver
$Drivespace = Get-wmiobject win32_logicaldisk -computername $ExchangeServers
foreach($Drive in $drivespace) {
$DrFree = $drivespace.deviceid.freespace
$DrSize = $drivespace.deviceid.volumename.size
$Databases = Get-MailboxDatabase * -Status
foreach($Database in $Databases) {
$DBSize = $Database.DatabaseSize
$MBCount = @(Get-MailboxStatistics -Database $Database.Name).Count
$MBAvg = Get-MailboxStatistics -Database $Database.Name |
%{$_.TotalItemSize.value.ToMb()} |
Measure-Object -Average
New-Object PSObject -Property @{
Server = $Database.Server.Name
DatabaseName = $Database.Name
LastFullBackup = $Database.LastFullBackup
MailboxCount = $MBCount
"DatabaseSize (GB)" = $DBSize.ToGB()
"AverageMailboxSize (MB)" = $MBAvg.Average
"WhiteSpace (MB)" = $Database.AvailableNewMailboxSpace.ToMb()
"Drive and Capacity" = $drsize.toGB()
"Drive Freespace" = $drfree.toGB()

Answer 1

Here is how you should approach this.  It is more efficient and will produce less errors.  I didn't test it I just wanted to point you in a better direction. 
Don't try to convert numbers until you have collected all of the data.  The formatter pass always comes at the end.
The WMI needs to be looked at.  I didn't look up how to get eth drive letter.  It needs to be extracted from the database file path.
function DatabaseStatistics{
$servers=get-exchangeserver
foreach($server in $servers){
$p=@{
Server=$server.Name
DatabaseName=$null
LastFullBackup=$null
MailboxCount=$null
DatabaseSize=$null
AverageMailboxSize=$null
WhiteSpace=$null
DriveSize=$null
DriveFreespace=$null
$databases=Get-MailboxDatabase -Server $server
foreach($database in $databases){
$p.DatabaseSize=$database.DataBaseSize
$p.DatabaseName=$database.Name
$values=Get-MailboxStatistics -Database *|%{$_.ToTalItemSize.Value}|Measure-Object -Average
$p.MailBoxCOunt=$values.Count
$p.AverageMailboxSize=$values.Average
$p.LastFullBackup=$database.LastFullBackup
$p.WhiteSpace=$database.AvailableNewMailboxSpace
$edbpath=$database.edbFilePath.PathName
$d=([io.fileinfo]$edbpath).Directory.Root.Name.Replace('\','') #'
$drv=Get-WmiObject Win32_LogicalDisk -Filter "Name='$d'" -Computer $server
$p.DriveSize=$drv.Size
$p.DriveFreeSpace=$drv.Freespace
New-Object PSObject -Property $p
DatabaseStatistics
¯\_(ツ)_/¯