Simple Powershell script to replace values in a .net configuration file

The following powershell script shows how to perform quick and dirty .net XML config file swapping. I use these quick swaps for our build server and continous deployments in Bamboo. This should work on Powershell version 2+.

There are two functions below:

  1. One for finding and replacing the key value pairs for AppSettings.
  2. Replacing the log4net RollingFileAppender filename.
# swap a key/value in AppSettings
Function swapAppSetting {
  param([string]$key,[string]$value )
  $obj = $doc.configuration.appSettings.add | where {$_.Key -eq $key }
  $obj.value = $value

# swap the log4net filename
Function swaplog4Net {
  param([string]$value )
  $fileAppender = $doc.configuration.log4net.appender | where {$_.Type -eq 'log4net.Appender.RollingFileAppender' }
  $log = $fileAppender.file
  $log.value = $value

$webConfig = "\\server\path\app.config"
$doc = [Xml](Get-Content $webConfig)

swaplog4Net 'server-custom-name.log'
swapAppSetting 'env' 'test'


Hopefully this saves you a few minutes.