C#計算器（組合框控件）

namespace WindowsFormsApplication5
{
    partial class Form1
    {
        /// <summary>
        /// 必需的設計器變量。
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// 清理所有正在使用的資源。
        /// </summary>
        /// <param name="disposing">如果應釋放託管資源，爲 true；否則爲 false。</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows 窗體設計器生成的代碼

        /// <summary>
        /// 設計器支持所需的方法 - 不要
        /// 使用代碼編輯器修改此方法的內容。
        /// </summary>
        private void InitializeComponent()
        {
            this.button1 = new System.Windows.Forms.Button();
            this.textBox1 = new System.Windows.Forms.TextBox();
            this.textBox2 = new System.Windows.Forms.TextBox();
            this.label1 = new System.Windows.Forms.Label();
            this.textBox3 = new System.Windows.Forms.TextBox();
            this.comboBox1 = new System.Windows.Forms.ComboBox();
            this.SuspendLayout();
            // 
            // button1
            // 
            this.button1.Location = new System.Drawing.Point(255, 185);
            this.button1.Name = "button1";
            this.button1.Size = new System.Drawing.Size(75, 23);
            this.button1.TabIndex = 0;
            this.button1.Text = "button1";
            this.button1.UseVisualStyleBackColor = true;
            this.button1.Click += new System.EventHandler(this.button1_Click);
            // 
            // textBox1
            // 
            this.textBox1.Location = new System.Drawing.Point(51, 75);
            this.textBox1.Name = "textBox1";
            this.textBox1.Size = new System.Drawing.Size(100, 21);
            this.textBox1.TabIndex = 2;
            // 
            // textBox2
            // 
            this.textBox2.Location = new System.Drawing.Point(266, 74);
            this.textBox2.Name = "textBox2";
            this.textBox2.Size = new System.Drawing.Size(100, 21);
            this.textBox2.TabIndex = 3;
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(385, 77);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(41, 12);
            this.label1.TabIndex = 4;
            this.label1.Text = "label1";
            // 
            // textBox3
            // 
            this.textBox3.Location = new System.Drawing.Point(448, 75);
            this.textBox3.Name = "textBox3";
            this.textBox3.Size = new System.Drawing.Size(100, 21);
            this.textBox3.TabIndex = 5;
            // 
            // comboBox1
            // 
            this.comboBox1.FormattingEnabled = true;
            this.comboBox1.Location = new System.Drawing.Point(184, 75);
            this.comboBox1.Name = "comboBox1";
            this.comboBox1.Size = new System.Drawing.Size(46, 20);
            this.comboBox1.TabIndex = 6;
           
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(607, 262);
            this.Controls.Add(this.comboBox1);
            this.Controls.Add(this.textBox3);
            this.Controls.Add(this.label1);
            this.Controls.Add(this.textBox2);
            this.Controls.Add(this.textBox1);
            this.Controls.Add(this.button1);
            this.Name = "Form1";
            this.Text = "Form1";
            this.Load += new System.EventHandler(this.Form1_Load);
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.Button button1;
        private System.Windows.Forms.TextBox textBox1;
        private System.Windows.Forms.TextBox textBox2;
        private System.Windows.Forms.Label label1;
        private System.Windows.Forms.TextBox textBox3;
        private System.Windows.Forms.ComboBox comboBox1;
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication5
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            label1.Text = "=";
            button1.Text = "運算";
            comboBox1.Items.Add("+");
            comboBox1.Items.Add("-");
            comboBox1.Items.Add("*");
            comboBox1.Items.Add("/");
           
        }
        string text;
    
        private void button1_Click(object sender, EventArgs e)
        {
            switch (comboBox1.Text)
            {
                case "+":
                    text = (double.Parse(textBox1.Text) + double.Parse(textBox2.Text)).ToString();
                    break;
                case "-":
                    text = (double.Parse(textBox1.Text) - double.Parse(textBox2.Text)).ToString();
                    break;
                case "*":
                    text = (double.Parse(textBox1.Text) * double.Parse(textBox2.Text)).ToString();
                    break;
                case "/":
                    text = (double.Parse(textBox1.Text) / double.Parse(textBox2.Text)).ToString();
                    break;
                default:
                    break;
            }
            textBox3.Text = text;
        }
    }
}