Check out example codes for "C# get all files in directory". It will help you in understanding the concepts better.

Code Example 1

string[] allfiles = Directory.GetFiles("path/to/dir", "*.*", SearchOption.AllDirectories);

Code Example 2

string[] filePaths = Directory.GetFiles(@"c:\MyDir\", "*.bmp",
                                         SearchOption.AllDirectories);
// returns:
// "c:\MyDir\my-car.BMP"
// "c:\MyDir\Friends\james.BMP"

Code Example 3

//path is the path of the directory to get files from
//searchPattern is to get specific files. If you want only exe files you enter *.exe

private static IEnumerable<string> GetAllFiles(string path, string searchPattern)
        {
            return Directory.EnumerateFiles(path, searchPattern).Union(
            Directory.EnumerateDirectories(path).SelectMany(d =>
            {
                try
                {
                    return GetAllFiles(d, searchPattern);
                } catch(Exception e)
                {
                    return Enumerable.Empty<string>();
                }
            }));
        }

Learn ReactJs, React Native from akashmittal.com