TextBox 스크롤 하단으로 내리기

textBox.SelectionStart = textBox.Text.Length;
textBox.ScrolltoCaret();

or

textBox.AppendText();

using System.Runtime.InteropServices;

private const int WM_VSCROLL = 0x115;
private const int SB_BOTTOM = 7;

[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern int SendMessage(intPtr hWnd, int wMsg, inPtr wParam, inPtr IParam);

SendMessage(textBox.Handle, WM_VSCROLL, (IntPtr)SB_BOTTOM, InPtr.Zero);