?using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void button16_Click(object sender, EventArgs e)
        {
            if (textBox1.Text != "")
                textBox1.Text = "";
            this.textBox1.Focus();
            
        }

        private void button11_Click(object sender, EventArgs e)
        {
            
            string str = textBox1.Text;
            int i;
            char c;
            string a="", b="";
           
                if (textBox1.Text != "")
                {
                    for (i = 0; (str[i] >= '0' && str[i] <= '9') || str[i] == '.'; i++)
                    {
                        a = a + str[i];
                    }
                    c = str[i];
                    for (int t = i + 1; t < str.Length; t++)
                    {
                        b = b + str[t];
                    }
                    switch (c)
                    {
                        case '+':

                            textBox1.Text = Convert.ToString(Convert.ToDouble(a) + Convert.ToDouble(b));
                            break;

                        case '-':

                            textBox1.Text = Convert.ToString(Convert.ToDouble(a) - Convert.ToDouble(b));
                            break;


                        case '*':

                            textBox1.Text = Convert.ToString(Convert.ToDouble(a) * Convert.ToDouble(b));
                            break;


                        case '/':

                            textBox1.Text = Convert.ToString(Convert.ToDouble(a) / Convert.ToDouble(b));
                            break;

                    }
                }
                else
                    textBox1.Text = "請輸入數字";
            
           
            
        }

        private void button1_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button1.Text;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button2.Text;
        }

        private void button3_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button3.Text;
        }

        private void button4_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button4.Text;
        }

        private void button5_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button5.Text;
        }

        private void button6_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button6.Text;
        }

        private void button7_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button7.Text;
        }

        private void button8_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button8.Text;
        }

        private void button9_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button9.Text;
        }

        private void button10_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button10.Text;
        }

        private void button12_Click(object sender, EventArgs e)
        {
           
            textBox1.Text = textBox1.Text + button12.Text;

        }

        private void button13_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button13.Text;
        }

        private void button15_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button15.Text;
        }

        private void button14_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button14.Text;
        }

        private void button17_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button17.Text;
        }

        private void textBox1_Click(object sender, EventArgs e)
        {
            textBox1.Text = "";
        }

        


        
    }
}