var files = Directory.GetFiles(jobDir);

var files = Directory.GetFiles(jobDir).Where(name => !name.EndsWith(".xml"));

var files = Array.FindAll(Directory.GetFiles(jobDir), x => !x.EndWith(".myext"))

string[] files = Directory.GetFiles(myDir);
foreach(string fileName in files)
{
    DoSomething(fileName);
}

var allFiles = Directory.GetFiles(@"C:Path", "");
  var filesToExclude = Directory.GetFiles(@"C:Path", "*.txt");
  var wantedFiles = allFiles.Except(filesToExclude);