How to use InsertAfter with PowerShell

Question

I have some xml files where I want to insert the contents of one xml file into another. I thought I'd use LastChild and the InsertAfter method to accomplish this. So far it's not working for me.

Here is the parent.xml file:

<manifest>
  <manifestExecution>
    <assetDetail>
      <fileAsset fileAssetGuid="parentguid1">
    <parentfile1 />
      </fileAsset>
      <fileAsset fileAssetGuid="parentguid2">
    <parentfile2 />
      </fileAsset>
    </assetDetail>
  </manifestExecution>
</manifest>

And here is the child.xml file:

<manifest>
  <manifestExecution>
    <assetDetail>
     <fileAsset fileAssetGuid="childguid1">
    <childfile1 />
     </fileAsset>
    </assetDetail>
  </manifestExecution>
</manifest>

What I want to do is select the fileAsset node(s) from child.xml and insert into parent.xml after the last fileAsset node in parent.xml.

Here is my test code:

$parent = [xml] (Get-Content d:\temp\parent.xml)
$parentnode = $parent.manifest.manifestExecution.assetDetail
$child = [xml] (Get-Content d:\temp\child.xml)
$childnode = $child.manifest.manifestExecution.assetDetail.InnerXml
$parentnode.InsertAfter($childnode, $parentnode.LastChild)

Here is the error msg I'm getting:

Cannot convert argument "0", with value: "<fileAsset fileAssetGuid="childguid1"> <childfile1 /></fileAsset>", for "InsertAfter" to type "System.Xml.XmlNode": "Cannot conver t the "<fileAsset fileAssetGuid="childguid1"><childfile1 /></fileAsset>" value of type "System.String" to type "System.Xml.XmlNode"." At line:5 char:24 + $parentnode.InsertAfter <<<< ($childnode, $parentnode.LastChild) + CategoryInfo : NotSpecified: (:) [], MethodException + FullyQualifiedErrorId : MethodArgumentConversionInvalidCastArgument

What am I doing wrong?

Joel B Fant · Accepted Answer · 2011-06-17T00:53:31.707

You need to iterate through $childnode's children, remove them from their parent, and import them into the new document context ($child and $parent are different XmlDocument instances) before appending to $parentnode.

This will append all fileAsset nodes from $childnode into $parentnode.

$parent = [xml](get-content d:\temp\parent.xml)
$parentnode = $parent.manifest.manifestexecution.assetdetail
$child = [xml](get-content d:\temp\child.xml)
$childnode = $child.manifest.manifestexecution.assetdetail

while ($childnode.haschildnodes) {
  $cn = $childnode.firstchild
  $cn = $childnode.removechild($cn)
  $cn = $parentnode.ownerdocument.importnode($cn, $true)
  $parentnode.appendchild($cn)
}

Fortunately, most of these methods return the same XmlNode or a new version of it, so the body of the while loop could chained together like this:

$parentnode.appendchild( $parentnode.ownerdocument.importnode( $childnode.removechild( $childnode.firstchild ), $true ))

InsertAfter(newChild,referenceChild) could also work, but would be done a little differently since it also needs a reference to the the node that it will be inserted after.

Hi Joel, thanks for the great feedback. Your code worked great! — Keith, Jun 17 '11 at 20:43

score 0 · Answer 2 · answered Jun 17 '11 at 00:49

your first problem is that you're not getting an XML element, but a string. You need to get an XML node from your XML document, but the shorthand method you're using is guessing you want a string. Usually you can force it by explicitly casting it over to [System.Xml.XmlElement], but that doesn't always work. You can reliably get an element using "SelectSingleNode".

You've not hit your second problem yet, but it's just around the corner. Once you've got XML, it still won't work because it's from a different XML document, so you need to "Import" the node. You'll want to tweak this to get the XML to align the way you envision, but the code works.

$parentString = @"
<manifest>
  <manifestExecution>
    <assetDetail>
      <fileAsset fileAssetGuid="parentguid1">
    <parentfile1 />
      </fileAsset>
      <fileAsset fileAssetGuid="parentguid2">
    <parentfile2 />
      </fileAsset>
    </assetDetail>
  </manifestExecution>
</manifest>
"@
$childString = @"
<manifest>
  <manifestExecution>
    <assetDetail>
     <fileAsset fileAssetGuid="childguid1">
    <childfile1 />
     </fileAsset>
    </assetDetail>
  </manifestExecution>
</manifest>
"@

$parent = [xml] ($parentString)
$parentnode = $parent.manifest.manifestExecution.assetDetail
$child = [xml] ($childString)
$xpath = '/manifest/manifestExecution/assetDetail'
$childnode = $child.SelectSingleNode($xpath)
Write-Host("So the child is $($childnode.OuterXML)")
$importedNode = $parent.ImportNode($childNode,$true)
Write-Host("And after importing: $($importedNode.OuterXML)")
$parentnode.InsertAfter($importednode, $parentnode.LastChild)
Write-Host("To finally yield: $($parent.OuterXML)")

Also, you may find you can use something like your original code if you cast it to XmlElement properly.

$childnode = [System.Xml.XmlElement]$child.manifest.manifestExecution.assetDetail.InnerXml

How to use InsertAfter with PowerShell

2 Answers2