When we build a C# project in Visual Studio, a file with extension .csproj is created, which lists the contents of the project and configures how it should be built. It's said that a .csproj file has XML format, however, I've been reading the book "Programming C#" by Ian Griffiths which said the format of a project file is "usually" XML. So I'm asking if there is any other formats for project files? If yes what are the formats and where are they used?
You can find good information in this document: Understanding the project file Microsoft Build Engine (MSBuild) project files are based on the MSBuild XML schema.