求助？急！
以下是中的程序，不知道错在什么地方？请高手支招啊！Const PI As Double = 3.1415926
Dim i As Integer = 0
Dim dou1 As Double = Me.TextBox2.Text
Dim r As Double = Double.Parse(dou1)
Dim dou2 As Double = Me.TextBox3.Text
Dim h As Double = Double.Parse(dou2)
Dim s As Double = 0, v As Double = 0, s1 As Double = 0, s2 As Double = 0,
i = Integer.Parse(Me.TextBox1.Text)
Select Case i
Case 1
s1 = PI * r * r
Me.Label8.Text = "圆柱的底面积为" + s1.ToString()
Case 2
s2 = 2 * PI * r * h
Me.Label8.Text = "圆柱的侧面积为" + s2.ToString()
Case 3
s = PI * r * r + 2 * PI * r * h
Me.Label8.Text = "圆柱的总面积为" + s.ToString()
Case 4
v = PI * r * r * h
Me.Label8.Text = "圆柱的体积为" + v.ToString()
调试时说S V S1 S2未定义，不是很明白，请指教！
