C#

private static bool FileInUse(string path)
       {
           FileInfo file = new FileInfo(path);
           FileStream stream = null;
           try
           {
               stream = file.Open(FileMode.Open, FileAccess.ReadWrite, FileShare.None);
           }
           catch (IOException ex)
           {
               //MessageBox.Show(ex.Message);
               //File in use
               return true;
           }
           finally
           {
               if (stream != null)
                   stream.Close();
           }
           return false;
       }