App.Config Transformation for projects which are not Web Projects in Visual Studio?

I tried several solutions and here is the simplest I personally found.
Dan pointed out in the comments that the original post belongs to Oleg Sych—thanks, Oleg!

Here are the instructions:

1. Add an XML file for each configuration to the project.

Typically you will have Debug and Release configurations so name your files App.Debug.config and App.Release.config. In my project, I created a configuration for each kind of environment, so you might want to experiment with that.

2. Unload project and open .csproj file for editing

Visual Studio allows you to edit .csproj files right in the editor—you just need to unload the project first. Then right-click on it and select Edit .csproj.

3. Bind App.*.config files to main App.config

Find the project file section that contains all App.config and App.*.config references. You'll notice their build actions are set to None and that's okay:

<None Include="App.config" />
<None Include="App.Debug.config" />
<None Include="App.Release.config" />

Next, make all configuration-specific files dependant on the main App.config so Visual Studio groups them like it does designer and code-behind files.

Replace XML above with the one below:

<None Include="App.config" />
<None Include="App.Debug.config" >
  <DependentUpon>App.config</DependentUpon>
</None>
<None Include="App.Release.config" >
  <DependentUpon>App.config</DependentUpon>
</None>

4. Activate transformations magic (still necessary for Visual Studio versions such as VS2019)

In the end of file after

<Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />

and before final

</Project>

insert the following XML -- please note there are two steps for the proper transformation to occur:

  <UsingTask TaskName="TransformXml" AssemblyFile="$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)\Web\Microsoft.Web.Publishing.Tasks.dll" />
  <Target Name="BeforeBuild" Condition="Exists('App.$(Configuration).config')">
    <!-- Generate transformed app config and replace it: will get the <runtime> node and assembly bindings properly populated -->
    <TransformXml Source="App.config" Destination="App.config" Transform="App.$(Configuration).config" />
  </Target>
  <Target Name="AfterBuild" Condition="Exists('App.$(Configuration).config')">
    <!-- Generate transformed app config in the intermediate directory: this will transform sections such as appSettings -->
    <TransformXml Source="App.config" Destination="$(IntermediateOutputPath)$(TargetFileName).config" Transform="App.$(Configuration).config" />
    <!-- Force build process to use the transformed configuration file from now on.-->
    <ItemGroup>
      <AppConfigWithTargetPath Remove="App.config" />
      <AppConfigWithTargetPath Include="$(IntermediateOutputPath)$(TargetFileName).config">
        <TargetPath>$(TargetFileName).config</TargetPath>
      </AppConfigWithTargetPath>
    </ItemGroup>
  </Target>

Now you can reload the project, build it and enjoy App.config transformations!

FYI

Make sure that your App.*.config files have the right setup like this:

<?xml version="1.0" encoding="utf-8"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
     <!--magic transformations here-->
</configuration>

---

This works now with the Visual Studio AddIn treated in this article: SlowCheetah - Web.config Transformation Syntax now generalized for any XML configuration file.

You can right-click on your web.config and click "Add Config Transforms." When you do this, you'll get a web.debug.config and a web.release.config. You can make a web.whatever.config if you like, as long as the name lines up with a configuration profile. These files are just the changes you want made, not a complete copy of your web.config. You might think you'd want to use XSLT to transform a web.config, but while they feels intuitively right it's actually very verbose. Here's two transforms, one using XSLT and the same one using the XML Document Transform syntax/namespace. As with all things there's multiple ways in XSLT to do this, but you get the general idea. XSLT is a generalized tree transformation language, while this deployment one is optimized for a specific subset of common scenarios. But, the cool part is that each XDT transform is a .NET plugin, so you can make your own. NewSetting New Setting Value Or the same thing via the deployment transform:

---

Another solution I've found is NOT to use the transformations but just have a separate config file, e.g. app.Release.config. Then add this line to your csproj file.

  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|x86' ">
    <AppConfig>App.Release.config</AppConfig>
  </PropertyGroup>

This will not only generate the right myprogram.exe.config file but if you're using Setup and Deployment Project in Visual Studio to generate MSI, it'll force the deployment project to use the correct config file when packaging.

---

Inspired by Oleg and others in this question, I took the solution https://stackoverflow.com/a/5109530/2286801 a step further to enable the following.

Works with ClickOnce

Works with Setup and Deployment projects in VS 2010

Works with VS2010, 2013, 2015 (didn't test 2012 although should work as well).

Works with Team Build. (You must install either A) Visual Studio or B) Microsoft.Web.Publishing.targets and Microsoft.Web.Publishing.Tasks.dll)

This solution works by performing the app.config transformation before the app.config is referenced for the first time in the MSBuild process. It uses an external targets file for easier management across multiple projects.

Instructions:

Similar steps to the other solution. I've quoted what remains the same and included it for completeness and easier comparison.

0. Add a new file to your project called AppConfigTransformation.targets

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <!-- Transform the app config per project configuration.-->
  <PropertyGroup>
    <!-- This ensures compatibility across multiple versions of Visual Studio when using a solution file.
         However, when using MSBuild directly you may need to override this property to 11.0 or 12.0 
         accordingly as part of the MSBuild script, ie /p:VisualStudioVersion=11.0;
         See http://blogs.msdn.com/b/webdev/archive/2012/08/22/visual-studio-project-compatability-and-visualstudioversion.aspx -->
    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">10.0</VisualStudioVersion>
  </PropertyGroup>

  <Import Project="$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v$(VisualStudioVersion)\Web\Microsoft.Web.Publishing.targets" />

  <Target Name="SetTransformAppConfigDestination" BeforeTargets="PrepareForBuild" 
          Condition="exists('app.$(Configuration).config')">
    <PropertyGroup>
      <!-- Force build process to use the transformed configuration file from now on. -->
      <AppConfig>$(IntermediateOutputPath)$(TargetFileName).config</AppConfig>
    </PropertyGroup>
    <Message Text="AppConfig transformation destination: = $(AppConfig)" />
  </Target>

  <!-- Transform the app.config after the prepare for build completes. -->
  <Target Name="TransformAppConfig" AfterTargets="PrepareForBuild" Condition="exists('app.$(Configuration).config')">
    <!-- Generate transformed app config in the intermediate directory -->
    <TransformXml Source="app.config" Destination="$(AppConfig)" Transform="app.$(Configuration).config" />
  </Target>

</Project>

1. Add an XML file for each configuration to the project. Typically you will have Debug and Release configurations so name your files App.Debug.config and App.Release.config. In my project, I created a configuration for each kind of enironment so you might want to experiment with that. 2. Unload project and open .csproj file for editing Visual Studio allows you to edit .csproj right in the editor—you just need to unload the project first. Then right-click on it and select Edit .csproj.

3. Bind App.*.config files to main App.config

Find the project file section that contains all App.config and App.*.config references and replace as follows. You'll notice we use None instead of Content.

<ItemGroup>
  <None Include="app.config"/>
  <None Include="app.Production.config">
    <DependentUpon>app.config</DependentUpon>
  </None>
  <None Include="app.QA.config">
    <DependentUpon>app.config</DependentUpon>
  </None>
  <None Include="app.Development.config">
    <DependentUpon>app.config</DependentUpon>
  </None>
</ItemGroup>

4. Activate transformations magic In the end of file after and before final

insert the following XML:

<Import Project="AppConfigTransformation.targets" />

Done!

---

In my experience, the things I need to make environment-specific are things like connection strings, appsettings and often smpt settings. The config system allows to specify these things in separate files. So you can use this in your app.config/web.config:

 <appSettings configSource="appsettings.config" />
 <connectionStrings configSource="connection.config" />
 <system.net>
    <mailSettings>
       <smtp configSource="smtp.config"/>
    </mailSettings>
 </system.net>

What I typically do is to put these config-specific sections in separate files, in a subfolder called ConfigFiles (either in the solution root or at the project level, depends). I define a file per configuration, e.g. smtp.config.Debug and smtp.config.Release.

Then you can define a pre-build event like so:

copy $(ProjectDir)ConfigFiles\smtp.config.$(ConfigurationName) $(TargetDir)smtp.config

In team development, you can tweak this further by including the %COMPUTERNAME% and/or %USERNAME% in the convention.

Of course, this implies that the target files (x.config) should NOT be put in source control (since they are generated). You should still add them to the project file and set their output type property to 'copy always' or 'copy if newer' though.

Simple, extensible, and it works for all types of Visual Studio projects (console, winforms, wpf, web).

---

You can use a separate config file per configuration, e.g. app.Debug.config, app.Release.config and then use the configuration variable in your project file:

<PropertyGroup>
    <AppConfig>App.$(Configuration).config</AppConfig>
</PropertyGroup>

This will then create the correct ProjectName.exe.config file depending on the configuration you are building in.

---

I wrote nice extension to automate app.config transformation like the one built in Web Application Project Configuration Transform

The biggest advantage of this extension is that you don’t need to install it on all build machines

---

Install "Configuration Transform Tool" in Visual Studio from Marketplace and restart VS. You will be able to see menu preview transform for app.config as well.

https://marketplace.visualstudio.com/items?itemName=GolanAvraham.ConfigurationTransform

---

Just a little improvement to the solution that seems to be posted everywhere now:

<UsingTask TaskName="TransformXml" AssemblyFile="$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v$(VisualStudioVersion)\Web\Microsoft.Web.Publishing.Tasks.dll" />

that is, unless you are planning to stay with your current VS version forever

---

So I ended up taking a slightly different approach. I followed Dan's steps through step 3, but added another file: App.Base.Config. This file contains the configuration settings you want in every generated App.Config. Then I use BeforeBuild (with Yuri's addition to TransformXml) to transform the current configuration with the Base config into the App.config. The build process then uses the transformed App.config as normal. However, one annoyance is you kind of want to exclude the ever-changing App.config from source control afterwards, but the other config files are now dependent upon it.

  <UsingTask TaskName="TransformXml" AssemblyFile="$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v$(VisualStudioVersion)\Web\Microsoft.Web.Publishing.Tasks.dll" />
  <Target Name="BeforeBuild" Condition="exists('app.$(Configuration).config')">
    <TransformXml Source="App.Base.config" Transform="App.$(Configuration).config" Destination="App.config" />
  </Target>

---

I have created another alternative to the one posted by Vishal Joshi where the requirement to change the build action to Content is removed and also implemented basic support for ClickOnce deployment. I say basic, because I didn't test it thoroughly but it should work in the typical ClickOnce deployment scenario.

The solution consists of a single MSBuild project that once imported to an existent windows application project (*.csproj) extends the build process to contemplate app.config transformation.

You can read a more detailed explanation at Visual Studio App.config XML Transformation and the MSBuild project file can be downloaded from GitHub.

---

If you use a TFS online(Cloud version) and you want to transform the App.Config in a project, you can do the following without installing any extra tools. From VS => Unload the project => Edit project file => Go to the bottom of the file and add the following:

<UsingTask TaskName="TransformXml" AssemblyFile="$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v$(VisualStudioVersion)\Web\Microsoft.Web.Publishing.Tasks.dll" />
<Target Name="AfterBuild" Condition="Exists('App.$(Configuration).config')">
<TransformXml Source="App.config" Transform="App.$(Configuration).config" Destination="$(OutDir)\$(AssemblyName).dll.config" />

AssemblyFile and Destination works for local use and TFS online(Cloud) server.

---

proposed solution will not work when a class library with config file is referenced from another project (in my case it was Azure worker project library). It will not copy correct transformed file from obj folder into bin\##configuration-name## folder. To make it work with minimal changes, you need to change AfterCompile target to BeforeCompile:

<Target Name="BeforeCompile" Condition="exists('app.$(Configuration).config')">

---

Note: Due to reputation I cannot comment on bdeem's post. I'm posting my findings as an answer instead.

Following bdeem's post, I did the following (in order):

1. I modified the [project].csproj file. Added the <Content Include="" /> tags to the ItemGroup for the different config files and made them dependent on the original config file.

Note: Using <None Include="" /> will not work with the transformation.

<!-- App.config Settings -->
<!-- Create App.($Configuration).config files here. -->
<Content Include="App.config" />
<Content Include="App.Debug.config">
  <DependentUpon>App.config</DependentUpon>
</Content>
<Content Include="App.Release.config">
  <DependentUpon>App.config</DependentUpon>
</Content>

2. At the bottom of the [project].csproj file (before the closing </Project> tag), I imported the ${MSBuildToolsPath\Microsoft.CSharp.targets file, added the UsingTask to transform the XML and added the Target to copy the transformed App.config file to the output location.

Note: The Target will also overwrite the App.Config in the local directory to see immediate changes working locally. The Target also uses the Name="Afterbuild" property to ensure the config files can be transformed after the executables are generated. For reasons I do not understand, when using WCF endpoints, if I use Name="CoreCompile", I will get warnings about the service attributes. Name="Afterbuild" resolved this.

  <!-- Task to transform the App.config using the App.($Configuration).config file. -->
  <UsingTask TaskName="TransformXml" AssemblyFile="$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v$(VisualStudioVersion)\Web\Microsoft.Web.Publishing.Tasks.dll" />

  <!-- Only compile the App.config if the App.($Configuration).config file exists. -->
  <!-- Make sure to use the AfterBuild name instead of CoreCompile to avoid first time build errors and WCF endpoint errors. -->
  <Target Name="AfterBuild" Condition="exists('App.$(Configuration).config')">
    <!-- Generate transformed App.config in the intermediate output directory -->    
    <TransformXml Source="App.config" Destination="$(IntermediateOutputPath)$(TargetFileName).config" Transform="App.$(Configuration).config" />
    
    <!-- Modify the original App.config file with the transformed version. -->
    <TransformXml Source="App.config" Destination="App.config" Transform="App.$(Configuration).config" />

    <!-- Force build process to use the transformed configuration file from now on. -->
    <ItemGroup>
      <AppConfigWithTargetPath Remove="App.config" />
      <AppConfigWithTargetPath Include="$(IntermediateOutputPath)$(TargetFileName).config">
        <TargetPath>$(TargetFileName).config</TargetPath>
      </AppConfigWithTargetPath>
    </ItemGroup>
  </Target>
</Project>

3. Went back into Visual Studio and reloaded the modified files.

4. Manually added the App.*.config files to the project. This allowed them to group under the original App.config file.

Note: Make sure the App.*.config files have the proper XML structure.

<?xml version="1.0" encoding="utf-8"?>

<!-- For more information on using web.config transformation visit https://go.microsoft.com/fwlink/?LinkId=125889 -->

<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
  <connectionStrings>
    <add name="myConn" connectionString=""; Initial Catalog=; User ID=; Password=;" xdt:Transform="SetAttributes" xdt:Locator="Match(name)" />
  </connectionStrings>
</configuration>

5. Re-built the project.

---

Yet another variation on @bdeem's answer using Visual Studio 2019 and 2022. My issue was that using that solution, App.config was getting overwritten, and since it's in source control that's not really an option.

The solution for me was to transform the config file directly into the output directory.

  <UsingTask TaskName="TransformXml" AssemblyFile="$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)\Web\Microsoft.Web.Publishing.Tasks.dll" />
  <Target Name="AfterBuild" Condition="Exists('App.$(Configuration).config')">
    <!-- Generate transformed app config to the output directory -->
    <TransformXml Source="App.config" Destination="$(OutDir)\$(TargetFileName).config" Transform="App.$(Configuration).config" />
  </Target>

It has the added benefit of being quite a bit shorter than the original solution.

---