设置字体大小无法这么写，

    button1.Font.Size = 20；

这个是只读属性；

把字体大小改为16，

    button2.Font = new Font(button2.Font.Name, 16);

程序运行的时候先看一下窗体和控件的默认字体尺寸，都是9；然后点button4把button2的字体调为16，结果如下；

然后点button3，把窗体的字体大小改为16，再输出窗体和控件的字体大小，结果如下；

控件的字体也会同时变为16；如果把窗体的字体调大，窗体尺寸会变大；

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 fontdemo
{public partial class Form1 : Form{public Form1(){InitializeComponent();}private void Form1_Load(object sender, EventArgs e){textBox1.Text = this.Font.Size.ToString();textBox2.Text = button1.Font.Size.ToString();}private void button4_Click(object sender, EventArgs e){button2.Font = new Font(button2.Font.Name, 16);}private void button3_Click(object sender, EventArgs e){this.Font = new Font(this.Font.Name, 16);textBox1.Text = this.Font.Size.ToString();textBox2.Text = button1.Font.Size.ToString();}}
}