vb.net小问题

如代码,这是个CLICK事件:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim r, s As String

r = TextBox1.Text

s = r ^ 2 * 3.1415

TextBox2.Text = s

问题是为什么不能改成这样:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

TextBox2.text=TextBox1.texe^2*3.1415 '(省去了定义变量)

我测试过,这样肯定不成立,是不是很个对象或控件都必须要先声明某个类型?

我是菜鸟,恳求高手指点迷津!!

把Dim r, s As String

r = TextBox1.Text

s = r ^ 2 * 3.1415

TextBox2.Text = s

改为：

Dim r，s As Double

r = CDbl（TextBox1.Text）

s = r ^ 2 * 3.1415

TextBox2.Text = s

就好了

也就是说用一个强制类型转换就解决了！

字符和数就运算不了的.