public delegate void ModifyProgressBarDelegate(int max, int val);
        public void ModifyProgressBarMethod(int max, int val)
        {
            progressBar1.Maximum = max;
            progressBar1.Value = val;
        }
        protected static List<string> FileINFolder(string patch)
        {
            var dir = new DirectoryInfo(patch);
            var files = new List<string>();
            bool x = false;
            int max = dir.GetFiles().Length;
            int val = 0;
            Thread b = new Thread(() => progressBar1.Dispatcher.BeginInvoke(new ModifyProgressBarDelegate(ModifyProgressBarMethod), max, val)); //Ругается на эту строчку
            b.Start();
            foreach (FileInfo file in dir.GetFiles())
            {
                if (file.Extension == ".xml")
                {
                    x = true;
                    files.Add(file.FullName);
                    val++;
                }

            }
            if (x == false)
            {
                System.Windows.MessageBox.Show("Не найдены файлы!");
            }

            return files;
        }