[英]How can I add an error message to my program if the user doesn't enter an integer?
[英]How can I add an error message when user does not enter text into second line of multiple line textbox?
當用戶沒有鍵進入第二行時,我需要向文本框添加一條錯誤消息,但是我嘗試的代碼對我來說也沒用。我已經嘗試過text.lenght,line.count等等
Private Sub MeanButton_Click_2(sender As Object, e As EventArgs) Handles MeanButton.Click
If Not InputNumberTextBox.Text = "" Then
MeanCalculateForm.Show()
MeanCalculateForm.InputNumberListBox.Items.AddRange(InputNumberTextBox.Lines)
MeanCalculateForm.ResultListBox.Items.Clear()
Me.Hide()
Else
MsgBox("Please enter more number to calculate")
End If
End Sub
圖片截圖:
https://ibb.co/58cd7YC
您可以創建自己的函數來檢查String
,在這種情況下InputNumberTextBox.Text
包含如下有效數字:
Private Function IsValidNumberFromText(ByVal Input As String) As Boolean
Try
Dim Check As Integer = CInt(Input)
Catch Ex As Exception
Return False
End Try
Return True
End Function
然后就做:
If IsValidNumberFromText(InputNumberTextBox.Text) ...
這可確保String
僅包含有效數字。
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