然后在button1 事件中添加计算和显示结果代码即可. Public Class Form1 Const P = 3.14 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click TextBox2.Clear() '清空以前计算结果 TextBox3.Clear() '清空以前计算结果 If TextBox1.Text <> String.Empty Then '判断是否输入半径 Dim r As Double = TextBox1.Text '上面是这两部的合并 Dim r As Double ' r=TextBox1.Text TextBox2.Text = 2 * P * r TextBox3.Text = P * r * r Else MsgBox("请输入圆的半径") End If