C#的groupbox和字体修改

代码如下：

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 _3
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
                label1.ForeColor = Color.Red;

        }

        private void button2_Click(object sender, EventArgs e)
        {
            label1.ForeColor = Color.Blue;
        }

        private void button3_Click(object sender, EventArgs e)
        {
            Close();
        }

        private void button1_Click_1(object sender, EventArgs e)
        {
            float ss, ee;
            ss = Convert.ToSingle(textBox1.Text);
            ee = Convert.ToSingle(textBox2.Text);
            textBox3.Text = Convert.ToString(ss * ee);