Remove unwanted (empty) xmlns attribute added by appendChild

Question

I have this code:

function setupProject($projectFile) {
  [xml]$root = Get-Content $projectFile;

  $project = $root.Project;

  $beforeBuild = $root.CreateElement("Target", "");
  $beforeBuild.SetAttribute("name", "BeforeBuild");
  $beforeBuild.RemoveAttribute("xmlns");
  $project.AppendChild($beforeBuild);

  $root.Save($projectFile);
}

It should add a new <Target name="BeforeBuild" /> to the XML document.

But it also adds an empty xmlns="" attribute which I don't want. (It's actually Visual Studio which doesn't like this attribute!)

<Target name="BeforeBuild" xmlns="" />

I've already tried this code:

$beforeBuild.RemoveAttribute("xmlns");
$project.AppendChild($beforeBuild);
$beforeBuild.RemoveAttribute("xmlns");

Answer 1

The xmlns="" namespace (un)declaration has been added because your parent element is in a namespace and your child element is not.

If you don't want this namespace declaration added, the implication is that you want the child element to be in the same namespace as its parent, and the answer is to put it in this namespace at the time you create the element. That is, change the call CreateElement("Target", "") to specify the correct namespace.

Answer 2

As answered by Michael Kay, the best way to remove this unwanted namespace is creating the new child element in the same namespace as its parent:

function setupProject($projectFile) {
  [xml]$root = Get-Content $projectFile;

  $project = $root.Project;

  # UPDATE THIS LINE $beforeBuild = $root.CreateElement("Target", "");
  $beforeBuild = $root.CreateElement("Target", $project.NamespaceURI);
  $beforeBuild.SetAttribute("name", "BeforeBuild");
  $beforeBuild.RemoveAttribute("xmlns");
  $project.AppendChild($beforeBuild);

  $root.Save($projectFile);
}