Dev Azure Pipeline Web Config Transform

The web.config transform appears at first glance to be somewhat orphaned in Azure DevOps. If you are deploying to a WebApp then the pipeline wizard will probably have given you this snippet for your Build step:

- task: [email protected]
solution: '$(solution)'
msbuildArgs: '/p:DeployOnBuild=true /p:WebPublishMethod=Package /p:PackageAsSingleFile=true /p:SkipInvalidConfigurations=true /p:DesktopBuildPackageLocation="$(build.artifactStagingDirectory)\" /p:DeployIisAppPath="Default Web Site"'
platform: '$(buildPlatform)'
configuration: '$(buildConfiguration)'

To run config transforms you can add the additional parameter /p:TransformConfigFile=true to your msbuildArgs.

The replacement, of course, is the independent FileTransform task (which can also work within zip files). But once your site is packaged the Web.Release.Config is left behind; so you have to run the FileTransform task before, not after, the build step. (Similarly the WebAppDeployment task can’t transform a Web.Release.config that isn’t inside the package).

Slightly magically, the default parameter for the FileTransform is which is exactly what you typically want for web.Release.config transforms:

#xmlTransformationRules: '-transform **\*.Release.config -xml **\*.config-transform **\*.$(Release.EnvironmentName).config -xml **\*.config' # Optional

FileTransform can also do variable substitution, and you can have multiple FileTransform steps in your pipeline. I also like to see some diagnostic feedback so I include script step to show the xml transform result. But I put it before variable substitution, because the variables often include secrets:

- task: [email protected]
displayName: Transform Release.Config
folderPath: '$(System.DefaultWorkingDirectory)/Ui/'
enableXmlTransform: true
xmlTransformationRules: -transform **/*.Release.config -xml **/*.config

- task: [email protected]
displayName: "Confirm web.config transform"
targetType: 'inline'
script: 'cat $env:System_DefaultWorkingDirectory/Ui/web.config'
errorActionPreference: 'continue'

- task: [email protected]
displayName: Variable substitution *.config
folderPath: '$(System.DefaultWorkingDirectory)/Ui/'
fileType: 'xml'
targetFiles: '**/*.config'

- task: [email protected]


HowTo: Linux, Nginx, Mono, Asp.Net Mvc

These are notes I made for getting an application written for Asp.Net Mvc (It was probably Mvc 3-ish) to run on a Centos server.

Note that some of the issues/solutions may vary across Linux variants. The interface Nginx-Mono is FastCGI, which they both support. The Mono webserver is xsp4.

Of course, running cross platform is all much easier these days if you use .Net Core and Kestrel 🙂 And een for Net Framework running on Mono, the work done since Microsoft bought Xamarin has been really helpful for e.g. Mvc compatibility.

The Reading List

The Checklist

Ensure nginx has read execute permissions on your application directory and all parent directories

nginx conf section for webapp

With the Asp.Net website listening on port 9001

server {
listen 8080;

# use /smoketest/ to confirm that nginx is reading this config 
# and has read/execute access to the 
# /usr/share/nginx directories and files:

location /smoketest/ {
root /usr/share/nginx/smoketestredir;
index index.html;

# pass XSP to FastCGI server listening on
# use a different port for each ASP.NET site you create
# (port 9000 is often taken by PHP on default webserver setups)

location / {

# replace fastcgi with this to confirm nginx read address
# to files in root /usr/share/nginx/mywebapplication;
fastcgi_index index.html;

include /etc/nginx/fastcgi_params;
fastcgi_param  PATH_INFO          "";
fastcgi_param  SCRIPT_FILENAME    $document_root$fastcgi_script_name;

fastcgi_buffers 16 16k;
fastcgi_buffer_size 32k;

Systemd Startup Script

vim /etc/systemd/system/fastcgi-mono-hdmbreas.service

Description=FastCgi-mono-server4 for Application

ExecStart=/bin/fastcgi-mono-server4 --applications /:/usr/share/nginx/hdmbreas/hdm-fe-web --socket=tcp:

systemctl daemon-reload
systemctl start fastcgi-mono-app.service
systemctl status fastcgi-mono-app.service
systemctl status fastcgi-mono-app.service

Error: [error] 7216#0: *119 upstream sent too big header while reading response header

  • Considering setting the buffer size
  • Considering setting the busy buffer size
  • e.g. nginx config: fastcgi_buffers 16 16k; fastcgi_buffer_size 32k;

Watching Errors

Watch errors with tail -F /var/log/nginx/error.log

IIS Express : Run a child web application in a virtual directory under a parent application

Like this: Edit your IIS Express config file at

"%userprofile%\My Documents\IISExpress\config\applicationhost.config"

Create a site which has two applications defined in it, e.g.

<site name="MyTopLevelAndChildWebAppsInOneSite" id="123" >
    <application path="/" applicationPool="Clr4IntegratedAppPool">
        <virtualDirectory path="/" physicalPath="C:\Users\me\Source\TopLevelWebApp" />
    <application path="/Child" applicationPool="Clr4IntegratedAppPool">
        <virtualDirectory path="/" physicalPath="C:\Users\me\Source\ChildWebApp" />
        <binding protocol="http" bindingInformation="*:51234:localhost" />

And then run the site, matching it on the siteid:

start "Woo!" "C:\Program Files (x86)\IIS Express\iisexpress.exe" /siteid:123

Browse to, and close, your web apps in the usual way from the IIS Express icon in the systray.

Optionally, experience the pain that is web.config inheritance. But try not to.