Please excuse me if this is a poor question as I am not good with memory mapped files. I am using memory mapped files in my project. I am tracking the files in progress and
I think OpenExisting(String) will open a named MMF, which is for sharing memory across processes. I think what you want is a MMF from disc like you get from CreateFromFile(String). If you simply need a new MMF instance pass null as name to OpenExisting(String).
Otherwise maybe you should advance your question, so we can better understand you usecase.