c#：用switch case判斷分數等級

代碼如下：

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 demo
{
    public partial class Hello : Form      
    {
        public Hello()
        {
            InitializeComponent();            
        }

        private void Form1_Load(object sender, EventArgs e)  // 窗體載入
        {
            this.Text = "判斷分數等級";  // 設定标題欄
            this.Width = 600;  // 設定寬度
            this.Height = 300;  // 設定高度
        }

        private void btnOK_Click(object sender, EventArgs e)  // 執行求開平方
        {
            int inNum = int.Parse(textBox1.Text); // 讀取輸入字元串解析為數字
            Judge j = new Judge();  // 建立一個Judge對象
            switch (j.Level(inNum))  // j.Level(inNum)調用類的方法擷取傳回ABCD
            {
                case "A":
                    textBox2.Text = "優秀";
                    break;
                case "B":
                    textBox2.Text = "良好";
                    break;
                case "C":
                    textBox2.Text = "及格";
                    break;
                case "D":
                    textBox2.Text = "不及格";
                    break;
                default:
                    textBox2.Text = "你的成績有誤";
                    break;
            }

        }

        private void btnCancle_Click(object sender, EventArgs e)  // 重置
        {
            textBox1.Text = "";
            textBox2.Text = "";
        }
    }
    class Judge  // 判斷分數等級，傳回ABCD
    {
        public string Level(int num)
        {
            if (num >= 85)
                return "A";
            else if (75 <= num && num < 85)
                return "B";
            else if (60 <= num && num < 75)
                return "C";
            else return "D";
        }
    }
}
           

效果圖：