Web Config Transforms: Insert If Not Exists

Use xdt:Transform="InsertIfMissing" with the XmlTransform task in VS2012. It doesn't look like Microsoft has updated their documentation to reflect this yet.

In my case xdt:Transform="InsertIfMissing" did not work without xdt:Locator="Match(name)"

Try this alternative transformation for xdt:Transform="InsertIfMissing" :

<?xml version="1.0"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
  <nodeToInsertIfMissing xdt:Transform="Insert" />
  <nodeToInsertIfMissing xdt:Transform="Remove" xdt:Locator="XPath(/configuration/nodeToInsertIfMissing[2])" />
</configuration>

It should works following MSDN documentation:

Insert - adds the element that is defined in the transform file as a sibling to the selected element or elements. The new element is added at the end of any collection.

So, if the node already exists, we add the second one and then remove this node (2nd). Otherwise, we add the new, unique node but remove operation will fail.

Note: It seems not working with NuGet *.(un)install.xdt transformation. InsertIfMissing too.

Confirmed working in VS2015 and Package Manager Console Host Version 3.4.4.1321 (you can find this when you open the Package Manager Console).

This will insert if 'configuration\connectionStrings\add\@name' does not exist.

The app.config.install.xdt:

<?xml version="1.0" encoding="utf-8" ?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
    <connectionStrings xdt:Transform="InsertIfMissing">
        <add name="MyCs" provider="System.Data.SqlClient" connectionString="" xdt:Transform="InsertIfMissing" xdt:Locator="Match(name)"/>
    </connectionStrings>
</configuration>

The .nuspec file:

<files>
    <file src="app.config.install.xdt" target="content\app.config.install.xdt" />