Simplify 'if' condition

Question

How can I simplify this code?

  if (directory.Exists)
  {
    smallFileNames = directory.GetFiles("*.csv").Select(i => i.FullName).ToList();
    if(smallFileNames.Count == 0)
      smallFileNames = DivideIntoFiles(fileName);  
  }
  else
    smallFileNames = DivideIntoFiles(fileName);

I confused by identical lines...

Answer 1

List<string> smallFileNames = null;

if (directory.Exists)
{
    smallFileNames = directory.GetFiles("*.csv").Select(i => i.FullName).ToList();
}

if (smallFileNames == null || smallFileNames.Count == 0)
    smallFileNames = DivideIntoFiles(fileName);

Answer 2

Jumping in after the horse has bolted with a very minor different approach (using Any rather than Count and null).

IEnumerable<string> GetSmallFileNames(Directory directory, string fileName, string filter) 
{
   var smallFileNames = new List<string>();

   if (directory.Exists)
   {
       smallFileNames = directory.GetFiles(filter).Select(i => i.FullName);           
   }

   return smallFileNames.Any() ? smallFileNames : DivideIntoFiles(fileName);
}

Then used such as

IEnumerable<string> smallFileNames = GetSmallFileNames(directory, fileName, "*.csv");

Answer 3

...and you could simplify the second conditional by initializing smallFileNames :

List<string> smallFileNames = new List<string>

if (directory.Exists)
{
    smallFileNames = directory.GetFiles("*.csv").Select(i => i.FullName).ToList();
}

if (smallFileNames.Count == 0)
    smallFileNames = DivideIntoFiles(fileName);

However, the whole logic seems unclear to me: there seems to be a hidden relation between directory and fileName. I would consider reviewing the surrounding code also.