static void Main(string[] args)
{
Console.WriteLine("Application to find all the JPG files");

Console.WriteLine("=====================================");
Console.Write("Location:");

string location = Console.ReadLine();

// Delete file.txt
if (File.Exists(@"C:\file.txt"))
File.Delete(@"C:\file.txt");

// Create DirectoryInfo instance
DirectoryInfo di = new DirectoryInfo(location);

// Add valid DirectoryInfo instance into stack
if (di != null)
directoryStack.Push(di);

// stop looping when directoryStack items is equal to 0
while (directoryStack.Count != 0)
GetFiles();

Console.WriteLine("Success");
Console.ReadLine();
}

// Get and write all the "JPEG" files
static void GetFiles()
{
StreamWriter sw = System.IO.File.AppendText(@"C:\file.txt");

// Get latest Directory Information from stack
DirectoryInfo currentDirectory = directoryStack.Pop();

// Get all sub directories
DirectoryInfo[] getDirectories = currentDirectory.GetDirectories();

// Add all sub directories into stack
for (int i = 0; i < getDirectories.Length; i++)
directoryStack.Push(getDirectories[i]);

// Get all jpg files
FileInfo[] getFilesInfo = currentDirectory.GetFiles("*.jpg");

// Write jpg full details into file.txt
for (int j = 0; j < getFilesInfo.Length; j++)
sw.WriteLine(getFilesInfo[j].FullName);

// Get directory information
DirectoryInfo searchDirectory = new DirectoryInfo(searchLocation);

// Get all the "JPEG" within directory and it's subdirectories
FileInfo[] getFiles = searchDirectory.GetFiles("*.jpg", SearchOption.AllDirectories);

// Retrieve all match files information
for (int i = 0; i < getFiles.Length; i++)
Console.WriteLine(getFiles[i].FullName);