.csproj files are trivial to edit without tooling (the newer SDK-style projects at least; the others are merely easy). It helps to understand how MSBuild works,

.csproj files are trivial to edit without tooling (the newer SDK-style projects at least; the others are merely easy). It helps to understand how MSBuild works, though. .sln files are mostly needed for Visual Studio and they are not required. Fun fact: solution files can be built by MSBuild and are converted into a normal temporary MSBuild project first for that.