Using PowerShell to add a Contact to a CRM 2011 MarketingList (SOAP)

We had a user delete a Marketing List. I needed to recreate it. I went to a database backup and found the GUID of the deleted list.
Then I used the following SQL query to find the GUIDs of all the members of that list:

SELECT FullName
    ,ParentCustomerIdName
    ,[EntityId]
    ,[ListId]
    ,[ListMemberId]
  FROM [CRMDataBaseName].[dbo].[ListMember],[CRMDataBaseName].[dbo].Contact
  where ListId = '787b77ca-c47d-431b-863e-12a98969b097' AND 
  [EntityId] = ContactId
  order by LastName,FirstName

I saved the EntityId column to a text file, and then I used the following PowerShell code to loop through the GUIDs and add them to a new MarketingList

$ListMembers = Get-Content C:\IT\Temp\ListMemberGUIDs.txt
foreach ($EntityId in $ListMembers){
$xml = ""
$xml += "<s:Envelope xmlns:s='http://schemas.xmlsoap.org/soap/envelope/'>";
$xml += "  <s:Body>";
$xml += "    <Execute xmlns='http://schemas.microsoft.com/xrm/2011/Contracts/Services' xmlns:i='http://www.w3.org/2001/XMLSchema-instance'>";
$xml += "      <request i:type='b:AddMemberListRequest' xmlns:a='http://schemas.microsoft.com/xrm/2011/Contracts' xmlns:b='http://schemas.microsoft.com/crm/2011/Contracts'>";
$xml += "        <a:Parameters xmlns:c='http://schemas.datacontract.org/2004/07/System.Collections.Generic'>";
$xml += "          <a:KeyValuePairOfstringanyType>";
$xml += "            <c:key>ListId</c:key>";
$xml += "            <c:value i:type='d:guid' xmlns:d='http://schemas.microsoft.com/2003/10/Serialization/'>5deb4efb-4ed7-47f3-8e8e-bb487e0db423</c:value>";
$xml += "          </a:KeyValuePairOfstringanyType>";
$xml += "          <a:KeyValuePairOfstringanyType>";
$xml += "            <c:key>EntityId</c:key>";
$xml += "            <c:value i:type='d:guid' xmlns:d='http://schemas.microsoft.com/2003/10/Serialization/'>$($EntityId)</c:value>";
$xml += "          </a:KeyValuePairOfstringanyType>";
$xml += "        </a:Parameters>";
$xml += "        <a:RequestId i:nil='true' />";
$xml += "        <a:RequestName>AddMemberList</a:RequestName>";
$xml += "      </request>";
$xml += "    </Execute>";
$xml += "  </s:Body>";
$xml += "</s:Envelope>";
 
$url="http://crm.sardverb.com/SardVerbinnen/XRMServices/2011/Organization.svc/web"
 
$http_request = New-Object -ComObject Msxml2.XMLHTTP
$http_request.Open('POST', $url, $false)
$http_request.setRequestHeader("SOAPAction", "http://schemas.microsoft.com/xrm/2011/Contracts/Services/IOrganizationService/Execute")
$http_request.setRequestHeader("Content-Type", "text/xml; charset=utf-8")
$http_request.setRequestHeader("Content-Length", $xml.length)
$http_request.send($xml)
}