.PROJ File Extension

When a developer creates an application in Visual Studio, they start by creating a new project and associated project file. The project file contains all the information MSBuild needs to build the developer's project. While specific types of applications typically use specific types of Visual Studio project files (for example, C# applications typically use .CSPROJ project files), some user-created project files may use the generic .proj extension.

PROJ files are XML files that contain elements defined by the MSBuild XML schema. These elements tell MSBuild what items to build and how to build them. For example, the PROJ file may contain settings that tell MSBuild to build an application differently when targeting different operating systems. Some of the elements PROJ files contain include:

• <Project>: Used to identify the project file's XML schema and specify entry points for the build process.
• <PropertyGroup>: Used to define build configuration properties.
• <ItemGroup>: Used to add inputs, such as source code files, into the build system.
• <Target>: Used to specify and execute build operations.

How do I use a PROJ file to build a Visual Studio project?

To build a project, a developer invokes MSBuild.exe from the Windows command-line interface along with the name of their project file. For example, to build a project named MyProject.proj, a developer would enter the command MSBuild.exe MyProject.proj in the command prompt, along with any other appropriate command-line options.