Powershell script to move MSMQ messages between queues with support for transactions and partial sets based on size.

Move-MsmqMessages.ps1

<#
.SYNOPSIS
    Moves messages between queues.

.DESCRIPTION
    Moves messages between queues, move isn't really the right word as moving can only occur
    between a queue and its sub-queues but its the Verb allowed by Powershell.

    Is allows moving messages between queues of different transaction type. 

    It also supports to move messages in a single transaction. It does not prevent to send
    non-transactional to a transactional queue in a transactional. This means that the
    receives are not participating in the transaction and are lost if the transaction commit
    would fail!

.PARAMETER SourcePath
    The location of the source queue.

.PARAMETER DestinationPath
    The location of the destination queue.

.PARAMETER Size
    Moves a maximum number messages.

.EXAMPLE
    # Move all messages
    Move-MsmqMessages ".\PRIVATE$\queue-a" ".\PRIVATE$\queue-b"

.EXAMPLE
    # Move all messages in a transaction, only safe if both queues are transactional!
    Move-MsmqMessages ".\PRIVATE$\queue-a" ".\PRIVATE$\queue-b" -Transactional

.EXAMPLE
    # Move 10 messages 
    Move-MsmqMessages ".\PRIVATE$\queue-a" ".\PRIVATE$\queue-b" -BatchSize 10

.EXAMPLE
    # Move 10 messages in a transaction, only safe if both queues are transactional!
    Move-MsmqMessages ".\PRIVATE$\queue-a" ".\PRIVATE$\queue-b" -BatchSize 10 -Transactional

#>
Set-StrictMode -Version Latest

Add-Type -AssemblyName System.Messaging
Add-Type -AssemblyName System.Transactions

Function Move-MsmqMessages {
    param(
        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [string] $SourcePath,

        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [string] $DestinationPath,

        [switch] $Transactional,

        [int] $Size
    )

    $sourceQueue = New-Object System.Messaging.MessageQueue -Argumentlist $sourcePath, [System.Messaging.QueueAccessMode]::Receive
    $destinationQueue = New-Object System.Messaging.MessageQueue -Argumentlist $destinationPath, [System.Messaging.QueueAccessMode]::Send

    $scope = New-Object System.Transactions.TransactionScope

    $transactionType = If ($Transactional) { [System.Messaging.MessageQueueTransactionType]::Automatic } Else { [System.Messaging.MessageQueueTransactionType]::Single } 

    try {
        $count = 0;
        $msgEnum = $sourceQueue.GetMessageEnumerator2()
        foreach ($item in $msgEnum) {
            $count++

            if ($sourceQueue.Transactional) {
                $msg = $sourceQueue.Receive($transactionType) # Not using `ReceiveById(id)` or `$sourceQueue.RemoveCurrent($transactionType)`
            }
            else {
                $msg = $sourceQueue.Receive() # Not using `$item.RemoveCurrent() as that breaks the foreach "When you remove the current message, the cursor is moved to the next message".
            }

            if ($destinationQueue.Transactional) {
                $destinationQueue.Send($msg, $transactionType)
            }
            else {
                $destinationQueue.Send($msg)
            }

            if (($Size -gt 0) -and ($count -ge $Size)) {
                break
            }
        }
        if ($transactional) {
            $scope.Complete();
        }
        return $count;
    }
    finally {
        $msgEnum.Dispose()
        $scope.Dispose()
        $sourceQueue.Dispose()
        $destinationQueue.Dispose()
    }
    return 0;
}

Excellent! I was browsing and stumbled upon your fine script. It really saved me some hours of scripting. Thank you @ramonsmits!