Random pick a file from a given Folder

 static public int RandomNumber;
 static public int randomIndex;
 static Random random = new Random(DateTime.Now.Millisecond);;

        public string GetRadomFileFromGivenFolderPath()
        {
            if (FolderPath_RandomFiles.Text != " ")
            {
                // Get an array of all file paths in the specified folder
                string[] files = Directory.GetFiles(FolderPath_RandomFiles.Text);

                // If no files are found, return null
                if (files.Length == 0)
                {
                    UpdateRichTextBox("No Files found!");
                    return "null";
                }

                // Generate a random number between 0 and the number of files minus 1
                do
                {
                    // Generate a random number between 0 and the number of files minus 1
                    randomIndex = random.Next(0, files.Length - 1);

                } while (RandomNumber == randomIndex);

                RandomNumber = randomIndex;
                // Return the file path at the random index
                return RandomFilePath = files[randomIndex];
            }
            else
            {
                UpdateRichTextBox("Folder path for \"random Files Path\" not found!");
                return "null";
            }
        }