如何创建仅接受30到250之间的数字的TextBox

Question

如何在VB.Net 2010中创建一个只接受30到250之间的数字的TextBox.我需要将值存储在Integer中,以便我可以在计算中使用它.

Dim x As String = textbox1
Dim y As Integer

y = Cint(textbox1)

If x <= 29 then
Msg("cant accept")
Textbox1 = ""
End if

Answer 1

验证Validating事件处理程序中控件的内容,如果失败则取消该事件.如果控件包含无效文本,则会阻止控件失去焦点.然后,您可以放心使用内容,CInt或者使用或Convert.ToInt32.

Private Sub TextBox1_Validating(sender As Object, e As CancelEventArgs) Handles TextBox1.Validating
    Dim number As Integer

    If Not Integer.TryParse(TextBox1.Text, number) OrElse
       number < 30 OrElse
       number > 250 Then
        MessageBox.Show("Please enter an integer from 30 to 250.",
                        "Invalid Input",
                        MessageBoxButtons.OK,
                        MessageBoxIcon.Error)

        'Don't let the control lose focus.
        e.Cancel = True
    End If
End Sub