[C#]Implement EnumerateFiles with the FindFirstFile and FindNextFile APIs

private static readonly IntPtr INVALID_HANDLE_VALUE = new IntPtr(-1);

[DllImport("kernel32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto, SetLastError = true)]
private static extern IntPtr FindFirstFile(string pFileName, ref  WIN32_FIND_DATA pFindFileData);

[DllImport("kernel32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto, SetLastError = true)]
private static extern bool FindNextFile(IntPtr hndFindFile, ref  WIN32_FIND_DATA lpFindFileData);

[DllImport( "kernel32.dll" , SetLastError =  true )]
private  static  extern  bool  FindClose(IntPtr hndFindFile);

[Serializable, StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto), BestFitMapping(false)]
internal struct WIN32_FIND_DATA
{
	public FileAttributes dwFileAttributes;
	public uint ftCreationTime_dwLowDateTime;
	public uint ftCreationTime_dwHighDateTime;
	public uint ftLastAccessTime_dwLowDateTime;
	public uint ftLastAccessTime_dwHighDateTime;
	public uint ftLastWriteTime_dwLowDateTime;
	public uint ftLastWriteTime_dwHighDateTime;
	public uint nFileSizeHigh;
	public uint nFileSizeLow;
	public int dwReserved0;
	public int dwReserved1;
	[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
	public string cFileName;
	[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 14)]
	public string cAlternateFileName;
}

public IEnumerable<string> EnumerateFiles(string path, string searchPattern = "*.*", SearchOption searchOption = SearchOption.AllDirectories)
{
	IntPtr hFind = INVALID_HANDLE_VALUE;
	WIN32_FIND_DATA FindFileData = default(WIN32_FIND_DATA);

	hFind = FindFirstFile(Path.Combine(path, searchPattern), ref  FindFileData);
	if (hFind != INVALID_HANDLE_VALUE)
	{
		do
		{
			if (FindFileData.cFileName.Equals(@".") || FindFileData.cFileName.Equals(@".."))
				continue;

			if (searchOption == SearchOption.AllDirectories && ((FindFileData.dwFileAttributes & FileAttributes.Directory) == FileAttributes.Directory))
			{
				foreach (var file in EnumerateFiles(Path.Combine(path, FindFileData.cFileName)))
					yield return file;
			}
			else
			{
				yield return Path.Combine(path, FindFileData.cFileName);
			}
		}
		while (FindNextFile(hFind, ref  FindFileData));
	}
	FindClose(hFind);
}