c# - Move Files That Do Not Exist -

i need copy files local hard drive external hard drive. thought is, want copy files not exist. sure there easier way such, mind went first.

my thoughts on how accomplish this:
1) list of files on c: drive , write text file
2) list of files on l: drive (backup) , write text file
3) compare c: drive text file l: drive text file find files not exist
4) write results of files not exist array
5) iterate through newly created array , copy files l: drive

is there more effective/time efficient way accomplish task?

for sure don't want create text files listing file names, , compare them. inefficient , clunky. way walk through source directories looking files. go, you'll creating matching destination path each file. before copy file need decide whether or not copy it. if file exists @ destination path, skip copying.

some enhancements on might include skipping copying if file exists , last modified date/time , file size match. , on, i'm sure can imagine variants on this.

one thing might not want build list of files first, , start copying. may more efficient copy files iterating on source directory. example use directory.enumeratefiles in efficient way.

of course, don't need write program this. thousands exist, of quite effective.