c# winform richtextbox 锁屏和滚屏

MyRichTextBox

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Windows;
using System.Windows.Forms;

class MyRichTextBox : RichTextBox
{
    public bool mouseDown;
    public int selCurrent;
    public int selOrigin;
    public int selStart;
    public int selEnd;
    public int selTrough;
    public int selPeak;

    private int WM_SETFOCUS = 0x0007;
    private UInt32 EM_SETSEL = 0x00B1;

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, int wParam, int lParam);

    public MyRichTextBox()
    {
        this.MouseDown += new System.Windows.Forms.MouseEventHandler(this.rtb_MouseDown);
        this.MouseMove += new System.Windows.Forms.MouseEventHandler(this.rtb_MouseMove);
        this.MouseUp += new System.Windows.Forms.MouseEventHandler(this.rtb_MouseUp);
        this.KeyPress += new System.Windows.Forms.KeyPressEventHandler(this.rtb_KeyPress);
    }

    protected override void WndProc(ref Message m)
    {
        // Let everything through except for the WM_SETFOCUS message
        if (m.Msg != WM_SETFOCUS)
            base.WndProc(ref m);
    }

    public void rtb_MouseDown(object sender, MouseEventArgs e)
    {
        mouseDown = true;
        // reset all the selection stuff
        selOrigin = selStart = selEnd = selPeak = selTrough = GetCharIndexFromPosition(e.Location);
        highlightSelection(1, Text.Length - 1, false);
    }

    public void rtb_MouseUp(object sender, MouseEventArgs e)
    {
        mouseDown = false;
    }

    public void rtb_MouseMove(object sender, MouseEventArgs e)
    {
        if (mouseDown)
        {
            selCurrent = GetCharIndexFromPosition(e.Location);

            // First determine the selection direction
            // Note the +1 when selecting backwards because GetCharIndexFromPosition
            // uses the left edge of the nearest character
            if (selCurrent < selOrigin + 1)
            {
                // If the current selection is smaller than the previous selection,
                // recolour the now unselected stuff back to the default colour
                if (selCurrent > selTrough)
                {
                    highlightSelection(selTrough, selCurrent, false);
                }
                selTrough = selCurrent;
                selEnd = selOrigin + 1;
                selStart = selCurrent;
            }
            else
            {
                // If the current selection is smaller than the previous selection,
                // recolour the now unselected stuff back to the default colour
                if (selCurrent < selPeak)
                {
                    highlightSelection(selPeak, selCurrent, false);
                }
                selPeak = selCurrent;
                selStart = selOrigin;
                selEnd = selCurrent;
            }

            highlightSelection(selStart, selEnd);
        }
    }

    private void highlightSelection(int start, int end, bool highlight = true)
    {
        selectText(start, end);
        SelectionBackColor = highlight ? System.Drawing.Color.FromArgb(0,120,215) : this.BackColor;
        SelectionColor = highlight ? Color.White : this.ForeColor;
    }

    private void selectText(int start, int end)
    {
        SendMessage(Handle, EM_SETSEL, start, end);
    }

    private void InitializeComponent()
    {
            this.SuspendLayout();
            this.ResumeLayout(false);

    }

    private void rtb_KeyPress(object sender, KeyPressEventArgs e)
    {
        if (e.KeyChar == 0x03)   // ctrl + C
        {
            Clipboard.SetText(this.Text.Substring(this.selStart, this.selEnd - this.selStart));
        }
    }
}

锁屏，滚动

        private delegate void AddTalkMessageDelegate(string message);

        /// <summary>
        /// 在聊天对话框（txt_Message）中追加聊天信息
        /// </summary>
        /// <param name="message"></param>
        private void AddTalkMessage(string message)
        {
            if (myRichTextBox1.InvokeRequired)
            {
                AddTalkMessageDelegate d = new AddTalkMessageDelegate(AddTalkMessage);
                myRichTextBox1.Invoke(d, new object[] { message });
            }
            else
            {
                if (runflag)
                {
                    //设置光标的位置到文本尾   
                    myRichTextBox1.Select(myRichTextBox1.TextLength, 0);
                    //滚动到控件光标处   
                    myRichTextBox1.ScrollToCaret();
                }
                myRichTextBox1.AppendText(message);
            }
        }

        bool runflag = true;

        private void button3_Click(object sender, EventArgs e)
        {
            runflag = false;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            runflag = true;
        }

 参考资料：https://www.codeproject.com/Articles/361161/How-to-Csharp-Prevent-RichTextBox-from-auto-scroll

我放弃了，改为内部调用网页的形式展现