Question

Visual Basic，Visual Studio 2013

我的问题是如何更改此代码以读取在文本框中写入的任何函数，该程序未支付转换错误。

Public Function f(Byval x As Double) As Double

        Return x * x + 2 * x    <- how read this function from textbox ?

   End Function

我尝试其他的但没有工作：

Public Function f(x) As Double

   f = TextBox1.Text

End Function

Answer 1

您必须从文本框中读取值，检查它是否为数字，然后将该值传递给计算。

' in some code somewhere, like maybe a click event
Dim value As Double = 0
If IsNumeric(Textbox1.Text) Then
    value = f(CDbl(Textbox1.Text))
End If
' Do something useful with value

' the rest of the code . . .

Public Function f(Byval x As Double) As Double
    Return x * x + 2 * x
End Function

如何从文本框中读取函数f（x）

1 个答案: