Visual Studio - File Properties (Build Action, Copy to Output Directory)

Posted 2021-10-27 frankcui

Ref: MSDN (https://docs.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-2010/0c6xyb66(v=vs.100) )

Difference between Build action content and ‘Copy to output directory‘ in Visual Studio

Question:

In my project in Visual Studio, I have files that I want included in the output, but not compiled or embedded.

I am aware that there are 2 ways to accomplish this.

1. Setting the Build Action for the file to ‘Content‘
2. Setting the ‘Copy to Output Directory‘ to ‘Copy Always‘ or ‘Copy if newer‘

Can someone tell me what the difference is and which scenario is each of the options appropriate for?

 

Answer:

When setting the Build Action to Content, the file will not be compiled and will be put in the Content output group.

Whether the file gets copies or not depends on the Copy to Output Directory setting at that point.

Of course, if you set Copy Always on a file, it may get compiled and then copied.

See File Properties on MSDN:

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Build Action Property

The Build Action property indicates what Visual Studio does with a file when a build is executed. Build Action can have one of several values:

• None - The file is not included in the project output group and is not compiled in the build process. An example is a text file that contains documentation, such as a Readme file.

• Compile - The file is compiled into the build output. This setting is used for code files.

• Content - The file is not compiled, but is included in the Content output group. For example, this setting is the default value for an .htm or other kind of Web file.

• Embedded Resource - This file is embedded in the main project build output as a DLL or executable. It is typically used for resource files.

   Note

  The Build Action property is extensible. As a result, you may see additional options listed for this property that have been added by other products and features.

The default value for Build Action depends on the extension of the file that you add to the solution. For example, if you add a Visual Basic project to Solution Explorer, the default value for Build Action is Compile. This is because the extension .vb indicates a code file that can be compiled. File names and extensions appear in Solution Explorer.

Note that the name of the file in your project will not be the identifier for the managed resource in the assembly manifest (see Assembly Manifest for more information). The identifier will be namespace.filename.extension, where namespace is the value of the DefaultNamespace property in a Visual C# project or RootNamespaceproperty in a Visual Basic project. Filename and extension remain the same as their original designation. If the file is a .resx file, the project system will run resgen.exe on the file, creating a .resource file. The .resource file will be embedded in the assembly. Therefore, the assembly manifest will refer to the .resources file and not the .resx file.

For example, if you add the file MyFile.bmp to a project whose default namespace is MyProj, and set the build action to Embedded Resource, MyProj.MyFile.bmp will be the identifier in the assembly manifest. If you then add the file MyFile.resx to the project, the default build action will be Embedded Resource and MyProj.MyFile.resources will be the identifier in the assembly manifest.

Note that when the resource editor adds an image, it sets Build Action to None, because the .resx file references the image file. At build time, the image is pulled into the .resources file created out of the .resx file. The image can then easily be accessed by way of the strongly-typed class auto-generated for the .resx file. Therefore, you should not change this setting to Embedded Resource, because doing this would include the image two times in the assembly.

For more information about how to access resource files (compiled from .resx files) at run time, see ResourceManager. For more information about how to access all other embedded files and resources at run time, see GetManifestResourceStream.

Copy to Output Directory Property

This property specifies the conditions under which the selected source file will be copied to the output directory. Select Do not copy if the file is never to be copied to the output directory. Select Copy always if the file is always to be copied to the output directory. Select Copy if newer if the file is to be copied only when it is newer than an existing file of the same name in the output directory.

For information about changing the output directory, see Build Page, Project Designer (C#) or Compile Page, Project Designer (Visual Basic).

 Note

In smart device projects, the newness of a .dll or .exe file is determined by comparing the Win32 versions as follows:

If the device-side version is less than that of the desktop, the file is copied.

If the device-side version is greater than that of the desktop, the file is not copied.

If the versions are the same, a checksum comparison is made. If the checksums are the same, the file is not copied. If the checksums are different, the file is copied.

The newness of files other than .dll and .exe is based only on checksum.

 Note

Data files will be copied to a subfolder named Data Files in the output directory.