app.config名称是硬编码的还是可以修改的？

Question

I know that when building in VS, app.config gets copied to <configuration>/<app-name>.exe.config . I believe this copy step is performed by msbuild, which VS uses for building?

I've seen some suggestions that this can be customised through build settings or properties or something, but I can't find a definitive answer.

My two linked questions are:

1. Who/what copies the app.config file to the output directory during building? And at what point in the build?
2. Can I control the name of the file that is searched for eg change it to Jeff.config or {ConfigurationName}.cfg ?

Answer 1

Technically yes, but you may need to be mindful as you're getting deeper in the pipeline. If you'll check this file:

Windows\\Microsoft.NET\\Framework64\\v4.0.30319\\Microsoft.Common.targets

You can find couple of interesting targets:

PrepareForBuild: Prepare the prerequisites for building.

  <Target Name="PrepareForBuild" DependsOnTargets="$(PrepareForBuildDependsOn)">
    <ItemGroup>
      <AppConfigWithTargetPath Include="$(AppConfig)" Condition="'$(AppConfig)'!=''">
        <TargetPath>$(TargetFileName).config</TargetPath>
      </AppConfigWithTargetPath>
    </ItemGroup>

    <FindAppConfigFile PrimaryList="@(None)" SecondaryList="@(Content)" TargetPath="$(TargetFileName).config" Condition="'$(AppConfig)'==''">
      <Output TaskParameter="AppConfigFile" ItemName="AppConfigWithTargetPath"/>
      <Output TaskParameter="AppConfigFile" PropertyName="AppConfig"/>
    </FindAppConfigFile>

    <!-- Create the directories for intermediate and final build products, and any other arbitrary directories. -->
    <!-- We are going to continue on error here so that if the tree is read only we will still get intellisense -->
    <MakeDir Directories="$(OutDir);$(IntermediateOutputPath);@(DocFileItem->'%(RelativeDir)');@(CreateDirectory)" ContinueOnError="True"/>

  </Target>

which builds up AppConfigWithTargetPath ItemGroup (and this itemgroup is used in many other targets). And another target, which performs the actual copying - _CopyAppConfigFile :Copy the application config file.

  <Target
      Name="_CopyAppConfigFile"
      Condition=" '@(AppConfigWithTargetPath)' != '' "
      Inputs="@(AppConfigWithTargetPath)"
      Outputs="@(AppConfigWithTargetPath->'$(OutDir)%(TargetPath)')">

    <!--
        Copy the application's .config file, if any.
        Not using SkipUnchangedFiles="true" because the application may want to change the app.config and not have an incremental build replace it.
        -->
    <Copy
        SourceFiles="@(AppConfigWithTargetPath)"
        DestinationFiles="@(AppConfigWithTargetPath->'$(OutDir)%(TargetPath)')"
        OverwriteReadOnlyFiles="$(OverwriteReadOnlyFiles)"
        Retries="$(CopyRetryCount)"
        RetryDelayMilliseconds="$(CopyRetryDelayMilliseconds)"             
      UseHardlinksIfPossible="$(CreateHardLinksForAdditionalFilesIfPossible)" >
      <Output TaskParameter="DestinationFiles" ItemName="FileWrites"/>
    </Copy>
  </Target>

Knowing how it's being copied - you can affect what should be copied. Most clean way is to define\\overwrite a value in $(AppConfig) property - then everything will have to use this new specified config.

Depends on how you build things - you may need to create pre-solution file to hook in or modify explicitly your build script to pass extra parameters. Or you may search in your csproj files and edit file name directly there.