Visual Studio Code: “Program has more than one entry point defined”

Question

I created a C# project using Visual Studio Code. This project contains two .cs files, Addition.cs and Substraction.cs. Both files contain a main()

Answer 1

If both entry points are in the same project, setting the startup project wouldn't do anything anyway. You need to set the startup object.

This can be done in the project properties dialog in a full version of Visual Studio (look for "Startup object" under Application), or in the .csproj file by setting Project/PropertyGroup/StartupObject:

Example.Addition

Alternatively consider using a single Main() entry point which takes a command-line argument.