var foundFiles = dirSearch.GetFiles().Where(file => file.LastWriteTime >= dateTimePicker1.Value && file.LastWriteTime <= dateTimePicker2.Value);

foreach (string pth in listBox2.Items)
            {
            string a = pth.ToString();
            string fil = t_file.Text;
            string create_date = textBox1.Text;
            //string s_date = textBox2.Text;
            //string p_date = textBox3.Text;
    
            string[] allFoundFiles = Directory.GetFiles(a, fil, SearchOption.AllDirectories);
            foreach (string file_ in allFoundFiles)
            {

                dataGridView1.Invoke(new MethodInvoker(() => dataGridView1.Rows.Add(file_))); // добавление файлов в datagridview
                Thread.Sleep(100); // пауза
            }

            }