Question

我有问题。我需要防止在输入框中输入非数字字符和负数。目前我可以防止非数字字符。如何防止负数。请参阅下面的代码：

Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click
    Dim h1, h2, h3, h4, h5, h6, h7, homeTotal As Integer
    Dim v1, v2, v3, v4, v5, v6, v7, visitorsTotal As Integer
    Dim prompt, title, prompt1, title1 As String
    Dim dataHome As String
    Dim dataVisitor As String

    If String.IsNullOrEmpty(lblHome1st.Text) And String.IsNullOrEmpty(lblVisitors1st.Text) Then
        prompt = "Enter number of home runs: First inning."
        title = "Home Runs, first inning."
        dataHome = InputBox(prompt, title)

        If IsNumeric(dataHome) = False Then
            MessageBox.Show("Please enter only numeric values.", "Important Note", MessageBoxButtons.OK)

        Else
            h1 = Convert.ToInt32(dataHome)
            lblHome1st.Text = h1

            prompt1 = "Enter number of visitor runs: First inning."
            title1 = "Visitors Runs, first inning."
            dataVisitor = InputBox(prompt1, title1)

            If IsNumeric(dataVisitor) = False Then
                MessageBox.Show("Please enter only numeric values.", "Important Note", MessageBoxButtons.OK)
                lblHome1st.Text = ""
                lblHomeTotal.Text = ""
                lblVisitorsTotal.Text = ""

            Else
                v1 = Convert.ToInt32(dataVisitor)
                lblVisitors1st.Text = v1

                'Calculate totals
                homeTotal = h1
                visitorsTotal = v1

                'Display totals
                lblHomeTotal.Text = homeTotal
                lblVisitorsTotal.Text = visitorsTotal

                'Display in the list box
                listScoreBoard.Items.Add("Innings" & " Home team " & "Visitors")
                listScoreBoard.Items.Add("1" & ControlChars.Tab & h1 & ControlChars.Tab & v1)
            End If

        End If

Answer 1

E.g。

Dim number As Integer

If Not Integer.TryParse(inputText, number) OrElse number < 0 Then
    'Either inputText is not a number or it is a negative number.
End If

或：

Dim number As Integer

If Integer.TryParse(inputText, number) AndAlso number >= 0 Then
    'inputText is a non-negative number.
End If

TryParse类型的Integer方法不仅会验证，而且如果数据有效，它也会转换。一石二鸟。

Answer 2

如果您已经在表单上，请考虑使用TextBox。您可以使用TextBox，KeyPress或KeyUp将输入限制为Keydown。

在此示例中，您将丢弃以下任何一个按键： - 不是数字，或 - 不是第一个＆＃34;。＆＃34; （或者你将使用的任何小数标记）。

虽然这是一个简单的例子 - 我将把编码留作自己的练习。

这只是几行代码 - 用户无法输入任何错误，因此您减少了其他代码中的错误检查。

防止在输入框中输入非数字字符和负数？

2 个答案: