Please stop, stop now...

(BTW, assignment statement was on one line, I added breaks just so I could fit it into a screenshot)

If the text is too blurry:

int index;
string fileNameWithoutExt;
additionalData.MailImportConfigCode = (fileNameWithoutExt = schema.Remove(schema.LastIndexOf('.'))).Substring((index = fileNameWithoutExt.LastIndexOf('.') + 1), fileNameWithoutExt.Length - index);
}