private const int MAX_PATH = 255;
[DllImport("kernel32.dll", SetLastError=true, CharSet=CharSet.Auto)]
static extern uint GetLongPathName( string lpszShortPath, [Out] StringBuilder lpszLongPath, uint cchBuffer);
public static string GetLongPathName(string lpszShortPath)
{
StringBuilder sb = new StringBuilder(MAX_PATH);
GetLongPathName(lpszShortPath, sb, MAX_PATH);
return sb.ToString();
}