vb.net VB 防止负整数
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VB Prevent negative integers
提问by Fractal Fear
I am just starting my first class on VB, and my teacher hasn't responded to email in 48 hours and my project is due soon. I am hoping you guys can help me solve this. What I am trying to do is get a program to calculate the total of 3 text boxes and display it in a single label. The catch is, the input in the 3 text boxes cannot be a negative number. I am trying to set it so when a negative number is input it displays a message to enter positive numbers only. However every time I run the program it just calculates the text box with a negative number as 0 and completes the rest of the calculations. Here is my code:
我刚刚开始我的第一堂 VB 课，我的老师在 48 小时内没有回复电子邮件，我的项目即将到期。我希望你们能帮我解决这个问题。我想要做的是获得一个程序来计算 3 个文本框的总数并将其显示在单个标签中。问题是，3 个文本框中的输入不能是负数。我正在尝试设置它，以便在输入负数时显示一条消息，仅输入正数。但是，每次我运行该程序时，它只计算文本框的负数为 0 并完成其余的计算。这是我的代码：
Private Sub btnCalc_Click(sender As Object, e As EventArgs) Handles btnCalc.Click
Dim intPackA As Integer
Dim intPackB As Integer
Dim intPackC As Integer
Dim intCalc As Integer
Try
If txtPackA.Text Or txtPackB.Text Or txtPackC.Text <= 0 Then
lblCalc.Text = "Please enter positive numeric values"
End If
If txtPackA.Text >= 0 Then
intPackA = txtPackA.Text * 79.2
Else
lblCalc.Text = "Please enter positive numeric values"
End If
If txtPackB.Text >= 0 Then
intPackB = txtPackB.Text * 119.4
Else
lblCalc.Text = "Please enter positive numeric values"
End If
If intPackC >= 0 Then
intPackC = txtPackC.Text * 149.5
Else
lblCalc.Text = "Please enter positive numeric values"
End If
intCalc = intPackA + intPackB + intPackC
lblCalc.Text = "Package A: " & intPackA.ToString("c") + vbCrLf & "Package B: " & intPackB.ToString("c") + vbCrLf & "Package C: " & intPackC.ToString("c") + vbCrLf + vbCrLf & "Grand Total: " & intCalc.ToString("c")
Catch
lblCalc.Text = "Please enter positive numeric values"
End Try
End Sub
I know some of the else and if statements are redundant, however if you could give me some pointers on an easy way to condense and clean up as well I would appreciate it.
我知道一些 else 和 if 语句是多余的，但是如果你能给我一些关于压缩和清理的简单方法的指示，我将不胜感激。
采纳答案by Santosh
Instead of
代替
If txtPackA.Text Or txtPackB.Text Or txtPackC.Text <= 0 Then
lblCalc.Text = "Please enter positive numeric values"
End If
Use this
用这个
If txtPackA.Text <= 0 Then
lblCalc.Text = "Please enter positive numeric values"
txtPackA.Focus()
Exit Sub
ElseIf txtPackB.Text <= 0 Then
lblCalc.Text = "Please enter positive numeric values"
txtPackB.Focus()
Exit Sub
ElseIf txtPackC.Text <= 0 Then
lblCalc.Text = "Please enter positive numeric values"
txtPackC.Focus()
Exit Sub
End If
回答by Edper
Convert first your String input from Textbox into Integer (and store it to an Integer variable) using TryParsebefore comparing like:
TryParse在比较之前，首先将您的字符串输入从文本框转换为整数（并将其存储到整数变量）：
Dim valueA, valueB, valueC As Integer
Dim intPackA, intPackB, intPackC, intCalc As Integer
Int32.TryParse(txtPackA.Text, valueA)
Int32.TryParse(txtPackB.Text, valueB)
Int32.TryParse(txtPackC.Text, valueC)
If valueA <=0 Or valueB <= 0 Or valueC <= 0 Then
lblCalc.Text = "Please enter positive numeric values"
Exit Sub
End If
Do the rest youserlf or else you have no more to learn as a student.
剩下的你自己做，否则你作为学生就没有更多的东西可以学习了。
回答by matzone
You will need this ........
你会需要这个........
Private Sub TB_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtPackA.KeyPress, txtPackB.KeyPress, txtPackC.KeyPress
Dim sN As String = "0123456789"
Dim sO As String = Chr(8) & Chr(13) & Chr(1) & Chr(3) & Chr(22)
If Not (sN & sO).Contains(e.KeyChar) Then
e.Handled = True
End If
End Sub
Private Sub TB_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtPackA.TextChanged, txtPackB.TextChanged, txtPackC.TextChanged
lblCalc.Text = format(val(txtPackA.Text) + val(txtPackB.Text) + val(txtPackC.Text))
End Sub
