关于C#中的一个默认按钮问题，请牛人指教

Question

当我先画完第二个Newton图之后，再单击其他按钮，为什么我的按钮会出现多个默认按钮，点击并不响应，附件里有我的源代码，希望牛人指点，急！

Answer 1

这是我的代码
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;namespace exp1
{
    public partial class solution1 : Form
    {
        public solution1()
        {
            InitializeComponent();
        }
        public double[] x1 ={1,2,3,4,5,6,7};
        public double[] y1 ={0.368,0.135,0.050,0.018,0.007,0.002,0.001};
        public int showpic1=0;
        public int showpic2 = 0;
        private void button1_Click(object sender, EventArgs e)
        {
            double temp;
            temp = p(0.596);
            textBox1.Text = temp.ToString();
        }
        public double p(double xx)
        {
            double[] x ={ 0.4, 0.55, 0.65, 0.80, 0.95, 1.05 };
            double[] y ={ 0.41075, 0.57815, 0.69675, 0.90, 1.00, 1.25382 };
            int i, k;
            double pp = 0, m1, m2;
            for (i = 0; i <= 5; i++)
            {
                m1 = 1;
                m2 = 1;
                for (k = 0; k <= 5; k++)
                    if (k != i)
                    {
                        m1 *= xx - x[k];
                        m2 *= x[i] - x[k];
                    }
                pp += y[i] * m1 / m2;
            }
            return pp;
        }
        public double jc(int k)
        {
            
            int i,j;
            double s=0,m;
            for(i=0;i<=k;i++)
            {
                for(m=1,j=0;j<=k;j++)
                    if(j!=i)m*=x1[i]-x1[j];
                s+=y1[i]/m;
            }
            return s;
        }
        public double newton(double X)
        {
            double nt = y1[0], m;
            int i, j;
            for (i = 1; i <= 6; i++)
            {
                for (m = 1, j = 0; j <= i - 1; j++)
                    m *= X - x1[j];
                nt += jc(i) * m;
            }
            return nt;
        }        private void button2_Click(object sender, EventArgs e)
        {
            double temp;
            temp = p(0.99);
            textBox1.Text = temp.ToString();
        }                private void button4_Click(object sender, EventArgs e)
        {
            double temp;
            temp = newton(6.15);
            textBox2.Text = temp.ToString();
        }        private void button3_Click(object sender, EventArgs e)
        {
            double temp;
            temp = newton(1.8);
            textBox2.Text = temp.ToString();
        }        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            if (showpic1 == 1)
            {
                float[] x2 = new float[50];
                float[] y2 = new float[50];                for (int i = 0; i < 50; i++)
                {
                    if (i == 0)
                    {
                        x2[i] = 0;
                        y2[i] = (float)p(x2[i]);
                    }
                    else
                    {
                        x2[i] = x2[i - 1] + 0.04f;
                        y2[i] = (float)p(x2[i]);
                    }
                }                pictureBox1.SizeMode = PictureBoxSizeMode.Zoom;
                CurvePaint cp = new CurvePaint();
                cp.XkeduCount = 10;
                cp.YkeduCount = 10;
                cp.XvalueStrMoveleft = 15;
                pictureBox1.Image = cp.drawCurve(x2, y2, "Lagrange多项式", "Xi", "Yi");
            }
        }        private void button5_Click(object sender, EventArgs e)
        {
            showpic1 = 1;
            pictureBox1.Invalidate();
            pictureBox1.Update();
        }
       private void pictureBox2_Paint(object sender, PaintEventArgs e)
        {
            if (showpic2 == 1)
            {
                float[] x3 = new float[10];
                float[] y3 = new float[10];                for (int i = 0; i < 10; i++)
                {
                    if (i == 0)
                    {
                        x3[i] = 0;
                        y3[i] = (float)newton(x3[i]);
                    }
                    else
                    {
                        x3[i] = x3[i - 1] + 1.0f;
                        y3[i] = (float)newton(x3[i]);
                    }
                }                pictureBox2.SizeMode = PictureBoxSizeMode.Zoom;
                CurvePaint cp = new CurvePaint();
                cp.XkeduCount = 10;
                cp.YkeduCount = 10;
                cp.XvalueStrMoveleft = 15;
                pictureBox2.Image = cp.drawCurve(x3, y3, "Newton多项式", "Xi", "Yi");
            }
        }       /* private void button6_Click(object sender, EventArgs e)
        {
            showpic2 = 1;
            pictureBox2.Invalidate();
            pictureBox2.Update();
        }*/        private void solution1_Load(object sender, EventArgs e)
        {        }        private void button6_Click(object sender, EventArgs e)
        {
            showpic2 = 1;
            pictureBox2.Invalidate();
            pictureBox2.Update();        }        
    }
}