Once you have your .zip/.rar extracted you can use
System.IO.Directory.Exists(string path);
If however you want to verify the existence of this directory before extracting, and if you are okay with using external libraries. You could use the DotNetZip library.
You can create a Ionic.Zip.ZipFile
object from a stream in memory or directly from the files on the drive.
ZipFile objects have a method called ContainsEntry
using (Ionic.Zip.ZipFile myZip = ZipFile.Read("MyArchive.zip"))
{
if(myZip.ContainsEntry(string path))
{
//Something
}
}
This way you can know for certain that the directory you want exists before extracting