c# 根据半径计算圆的面积和周长

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Windows.Forms;namespace 圆的周长和面积{ public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void button1_Click(object sender, EventArgs e) { double pi = 3.14; double B; double P; B = double.Parse(txtB.Text); P = 2 * pi * B; lblResult.Text = Convert.ToString(P); } private void button2_Click(object sender, EventArgs e) { double pi = 3.14; double B; double P; B = Convert.ToDouble(txtB.Text); P = pi * B * B; lblResult.Text=Convert.ToString(P); } }}