Rosyln might support incremental compilation, but, to my knowledge, it's not exposed in visual studio still in any meaningful way. See for instance https://stackoverflow.com/questions/34585588/is-c-sharp-comp....

Compilation in VS occurs at the project level. When you change a single file in the project, the entire project must be recompiled to generate the assembly. Eclipse on the other hand can recompile at the level of individual files, which is way faster, fast enough that it auto-compiles for you on save and the updates the editor with all errors and warnings discovered. No other IDE I am aware of can do this effectively.