I am trying to use the XmlMerge class (described here) to add a node to the <HttpModules> section of web.config to install a component I have developed. A requirement is that the mode is added just before the Compression node.

I have got it basically working per Charles Nurse's guidelines - the node is being added in the right position. The only problem is that the "collision detection" that is supposedly built in to XmlMerge doesn't seem to work - even though I have set key="name" and collision="overwrite", my node is added each time my code runs, resulting in multiple duplicate nodes.

Here's my 01.00.00.config file:

< configuration>
  < nodes configfile="web.config">
    < node path="/configuration/system.web/httpModules/add[@name='Compression']" action="insertbefore" key="name" collision="overwrite">
      < add name="UrlSigning" type="Company.Modules.UrlSigning.UrlSigningModule, Company.Modules.UrlSigning" />
    < /node>
  < /nodes>
< /configuration>

I have tried another configuration that just adds the node at the end of the <httpModules> section, but this also doesn't detect when the node already exists:

    < node path="/configuration/system.web/httpModules" action="add" key="name" collision="overwrite">

Am I doing something wrong, or do I need to code my own collision detection?

I am running DNN 4.9.5 by the way.