要是只想分析目录的话可用Path类:
string fullFileName = @"C:\mydir\myfile.ext";
string directoryName = Path.GetDirectoryName(fullFileName );
string fileName = Path.GetFileName(fullFileName);
string fileNameWithoutExt= Path.GetFileNameWithoutExtension (fullFileName);
要是普通字符串的话用String的Split方法:
String.Split