求教“System.StackOverflowException”类型的未经处理的异常出现在 System.Windows.Forms.dll 中。

Question

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;namespace 飞思卡尔_上位机
{
    public partial class Form1 : Form
    {
        char Rdata;
        double channelA, channelB, channelC, channelD;
        bool isStart=false;
        int pointx = 0;
        float pointtempA = 0;
        float pointtempB = 0;
        float pointtempC = 0;
        float pointtempD = 0;
        Graphics pic;        public Form1()
        {
            InitializeComponent();
            Control.CheckForIllegalCrossThreadCalls = false;
        }        private void button2_Click(object sender, EventArgs e)
        {
            if (serialPort1.IsOpen)
            {
                serialPort1.Close();
            }
            else
                MessageBox.Show("串口已关闭");
        }        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                if (comboBox1.SelectedItem != null && comboBox2.SelectedItem != null)
                {
                    if (isStart)
                    {
                        isStart = false;
                        serialPort1.Close();
                        button1.Text = "打开串口";
                        timer1.Enabled = false;
                    }
                    else
                    {
                        isStart = true;
                        serialPort1.PortName = Convert.ToString(comboBox1.SelectedItem);
                        serialPort1.BaudRate = Convert.ToInt32(comboBox2.SelectedItem);
                        serialPort1.Open();
                        button1.Text = "关闭串口";
                        timer1.Enabled = true;
                    }
                }
                else
                {
                    MessageBox.Show("初始化设置不完整！", "提示", MessageBoxButtons.OK);
                }
            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.Message,"提示",MessageBoxButtons.OK);
            }
        }        private void Form1_Load(object sender, EventArgs e)
        {
            comboBox1.Items.Add("COM1");
            comboBox1.Items.Add("COM2");
            comboBox1.Items.Add("COM3");
            comboBox1.Items.Add("COM4");
            comboBox1.Items.Add("COM5");
            comboBox1.Items.Add("COM6");
            comboBox1.Items.Add("COM7");
            comboBox1.Items.Add("COM8");
            comboBox1.Items.Add("COM9");            comboBox2.Items.Add("4800");
            comboBox2.Items.Add("9600");
            comboBox2.Items.Add("14400");
            comboBox2.Items.Add("19200");
            comboBox2.Items.Add("38400");
            comboBox2.Items.Add("56000");
            comboBox2.Items.Add("115200");            pic = this.pictureBox1.CreateGraphics();
        }        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (timer1.Enabled == true) timer1.Enabled = false;
            if (serialPort1.IsOpen) serialPort1.Close();
            Close();
        }        private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
        {
            this.Invoke(new EventHandler(Conduct_data));        }        private void Conduct_data(object sender, EventArgs e)
        {
            string temp;
            Rdata = Convert.ToChar(serialPort1.ReadByte());            if ((Rdata)=='!')
            {
                char[] box=new char[5];
                int i = 0;
                while ((Rdata = Convert.ToChar(serialPort1.ReadByte()))!='!')
                {                    box[i] = Rdata;
                    i++;
                }                temp = new string(box);            
                textBox1.Text =temp.Trim();
                channelA = Convert.ToDouble(temp.Trim());
                textBox5.Text = Convert.ToString(3.3 / 256 * channelA);
            }            if ((Rdata) == '@')
            {
                char[] box = new char[5];                    
                int i = 0;
                while ((Rdata = Convert.ToChar(serialPort1.ReadByte())) != '@')
                {                    box[i] = Rdata;
                    i++;
                }
                temp = new string(box);
                textBox2.Text = temp.Trim();
                channelB = Convert.ToDouble(temp.Trim());
                textBox6.Text = Convert.ToString(3.3 / 256 * channelB);
            }            if ((Rdata) == '#')
            {
                char[] box = new char[5];
                int i = 0;
                while ((Rdata = Convert.ToChar(serialPort1.ReadByte())) != '#')
                {                    box[i] = Rdata;
                    i++;
                }
                temp = new string(box);
                textBox3.Text = temp.Trim();
                channelC = Convert.ToDouble(temp.Trim());
                textBox7.Text = Convert.ToString(3.3 / 256 * channelC);
            }            if ((Rdata) == '$')
            {
                char[] box = new char[5];
                int i = 0;
                while ((Rdata = Convert.ToChar(serialPort1.ReadByte())) != '$')
                {                    box[i] = Rdata;
                    i++;
                }
                temp = new string(box);
                textBox4.Text = temp.Trim();
                channelD = Convert.ToDouble(temp.Trim());
                textBox8.Text = Convert.ToString(3.3 / 256 * channelD);
            }
        }        private void timer1_Tick(object sender, EventArgs e)
        {
            pic.DrawLine(Pens.Green, pointx, pictureBox1.Height - ((pictureBox1.Height / 4) * pointtempD / 256), pointx + 1, pictureBox1.Height - ((pictureBox1.Height / 4) * (float)channelD / 256));
            pic.DrawLine(Pens.Yellow, pointx, 3 * pictureBox1.Height / 4 - ((pictureBox1.Height / 4) * pointtempC / 256), pointx + 1, 3 * pictureBox1.Height / 4 - ((pictureBox1.Height / 4) * (float)channelC / 256));
            pic.DrawLine(Pens.Orange, pointx, 2 * pictureBox1.Height / 4 - ((pictureBox1.Height / 4) * pointtempB / 256), pointx + 1, 2 * pictureBox1.Height / 4 - ((pictureBox1.Height / 4) * (float)channelB / 256));
            pic.DrawLine(Pens.Red, pointx, pictureBox1.Height / 4 - ((pictureBox1.Height / 4) * pointtempA / 256), pointx + 1, pictureBox1.Height / 4 - ((pictureBox1.Height / 4) * (float)channelA / 256));            pointtempA = (float)channelA;
            pointtempB = (float)channelB;
            pointtempC = (float)channelC;
            pointtempD = (float)channelD;
            pointx++;
            if (pointx == 490)
            {
                pic.Clear(Color.White);
                pointx = 0;
            }
        }    }
}做个上位机但出现这种问题，这是什么原因，该怎么解决？