2021-05-06

Transforms

You can apply little transforms by just writing XML transformation on configuration files. For instance here is one for adding a section to the system.web section of the configuration file

<?xml version="1.0"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
  <system.web>
    <machineKey xdt:Transform="Insert" decryptionKey="abc" validationKey="def" />
  </system.web>
</configuration>

Here is one for removing an attribute

<?xml version="1.0"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
  <system.web>
    <compilation xdt:Transform="RemoveAttributes(debug)" />
  </system.web>
</configuration>

How about changing an attribute based on matching the key?

<?xml version="1.0"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
  <appSettings>
    <add key"MaxUsers" value="3" xdt:Transform="SetAttributes" xdt:Locator="Match(key)" />
  </appSettings>
</configuration>

If you happen to be using Octopus Deploy they have a feature you can add to your IIS deployment task to run these transformations

Testing

There is a great little online testing tool at https://elmah.io/tools/webconfig-transformation-tester/ where you can plug in random things until you get them working.

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