Question

这是我的代码：当dblprevious大于dblcurrent时，它会调用invalidinput，但它会显示负输出，而我知道它必须简单

    Public Class Form1
'names the the class veriables
Dim dblCurrent As Double
Dim dblPervious As Double
Private Sub invalidinput()
    Const Message As String = "check your input"
    Const title As String = " Attention!"
    Const buttons = MessageBoxButtons.OK
    MessageBox.Show(Message, title, buttons)
End Sub

Private Sub Total()

    Dim dblTotalP As Double
    Dim dblTotalG As Double
    Const dblPerGC As Double = 5.15
    Const dbltMinC As Double = 19.69

    'stores the veriables
    Double.TryParse(txtCurrentreading.Text, dblCurrent)
    Double.TryParse(txtPerivousreading.Text, dblPervious)
    dblTotalG = dblCurrent - dblPervious
    dblTotalP = dblTotalG / 1000 * dblPerGC
    If dblTotalP < dbltMinC Then
        dblTotalP = dbltMinC
    End If


    'displays totals
    lblTotalG.Text = dblTotalG
    lblTotalP.Text = dblTotalP.ToString("C2")
End Sub

Private Sub bntExit_Click(sender As Object, e As EventArgs) Handles bntExit.Click
    Me.Close()

End Sub

Private Sub txtCurrentreading_keypress(sender As Object, e As KeyPressEventArgs) Handles txtCurrentreading.KeyPress
    'allows text box to accept only numbers and the back space key

    If (e.KeyChar < "0" OrElse e.KeyChar > "9") AndAlso e.KeyChar <> ControlChars.Back Then
        e.Handled = True
    End If

End Sub

Private Sub txtPerivousreading_keypess(sender As Object, e As KeyPressEventArgs) Handles txtPerivousreading.KeyPress
    'allows text box to accept only numbers and the back space key


    If (e.KeyChar < "0" OrElse e.KeyChar > "9") AndAlso e.KeyChar <> ControlChars.Back Then
        e.Handled = True
    End If

End Sub

Private Sub bntCalculate_Click(sender As Object, e As EventArgs) Handles bntCalculate.Click

    'determines which calculations to do
    If dblCurrent >= dblPervious Then
        Call Total()
    ElseIf dblPervious < dblCurrent Then
        Call invalidinput()
    End If
End Sub
End Class

Answer 1

当dblprevious大于时，它意味着调用invalidinput dblcurrent

变化：

If dblCurrent >= dblPervious Then
    Call Total()
ElseIf dblPervious < dblCurrent Then
    Call invalidinput()
End If

要：

If dblCurrent >= dblPervious Then
    Call Total()
Else
    Call invalidinput()
End If

您在If dblPervious < dblCurrent Then的else块中的原始支票直接与您的要求相矛盾！如果＆＃34; dblCurrent＆＃34;不大于或等于＆＃34; dblPervious＆＃34;，然后＆＃34; dblPervious＆＃34;必须大于＆＃34; dblCurrent＆＃34;，从而允许我们完全删除第二次检查。

为什么我的消息框不起作用

1 个答案: