C# 控件 RichTextBox 显示行号，并且与Panel相互联动

我们在使用到WINFORM窗体工作中，要求RichTextBox 加入行号；

之前有看到大牛们写的，但是太复杂繁多，而且有用双TextBox进行联动，非常不错，今天我们尝试RichTextBox +Panel相互联动如下效果.

左侧灰色为Panel，右侧为RichTextBox 控件

1：准备Panel画布如下代码，当接到文件字符后进行坐标解析，绘制行号。

private void showLineNo()
        {
            //获得当前坐标信息
            Point p = this.txtFileView.Location;
            int crntFirstIndex = this.txtFileView.GetCharIndexFromPosition(p);

            int crntFirstLine = this.txtFileView.GetLineFromCharIndex(crntFirstIndex);

            Point crntFirstPos = this.txtFileView.GetPositionFromCharIndex(crntFirstIndex);

            p.Y += this.txtFileView.Height;

            int crntLastIndex = this.txtFileView.GetCharIndexFromPosition(p);

            int crntLastLine = this.txtFileView.GetLineFromCharIndex(crntLastIndex);
            Point crntLastPos = this.txtFileView.GetPositionFromCharIndex(crntLastIndex);

            //准备画图
            Graphics g = this.panel2.CreateGraphics();

            Font font = new Font(this.txtFileView.Font, this.txtFileView.Font.Style);

            SolidBrush brush = new SolidBrush(Color.Green);

            //画图开始

            //刷新画布

            Rectangle rect = this.panel2.ClientRectangle;
            brush.Color = this.panel2.BackColor;

            g.FillRectangle(brush, 0, 0, this.panel2.ClientRectangle.Width, this.panel2.ClientRectangle.Height);

            brush.Color = Color.White;//重置画笔颜色

            //绘制行号

            int lineSpace = 0;

            if (crntFirstLine != crntLastLine)
            {
                lineSpace = (crntLastPos.Y - crntFirstPos.Y) / (crntLastLine - crntFirstLine);

            }

            else
            {
                lineSpace = Convert.ToInt32(this.txtFileView.Font.Size);

            }
            int brushX = this.panel2.ClientRectangle.Width - Convert.ToInt32(font.Size * 3);

            int brushY = crntLastPos.Y + Convert.ToInt32(font.Size * 0.21f);
            for (int i = crntLastLine; i >= crntFirstLine; i--)
            {

                g.DrawString((i + 1).ToString(), font, brush, brushX, brushY);

                brushY -= lineSpace;
            }

            g.Dispose();

            font.Dispose();

            brush.Dispose();
        }

2：事件准备（启用）如下事件

控件加载事件

private void txtFileView_TextChanged(object sender, EventArgs e)
        {
            showLineNo();
        }

控件滚动事件（当算出的行数大于本控件长度）

private void txtFileView_VScroll(object sender, EventArgs e)
        {
            showLineNo();
        }

完成后，直接启用运行，Demo事例中的效果就出来，方便大家用于各种应用上.