numerictextbox.vb

一个很不错的学生管理系统

Public Class NumericTextBox
    Inherits System.Windows.Forms.TextBox

#Region " Windows 窗体设计器生成的代码 "

    Public Sub New()
        MyBase.New()

        '该调用是 Windows 窗体设计器所必需的。
        InitializeComponent()

        '在 InitializeComponent() 调用之后添加任何初始化

    End Sub

    'UserControl1 重写 dispose 以清理组件列表。
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub

    'Windows 窗体设计器所必需的
    Private components As System.ComponentModel.IContainer

    '注意：以下过程是 Windows 窗体设计器所必需的
    '可以使用 Windows 窗体设计器修改此过程。
    '不要使用代码编辑器修改它。
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        '
        'NumericTextBox
        '
        Me.Name = "NumericTextBox"

    End Sub

#End Region


    Private Sub NumericTextBox_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles MyBase.KeyPress
        Dim KeyAscii As Integer
        KeyAscii = Asc(e.KeyChar)

        Select Case KeyAscii
            Case 48 To 57, 8, 13
                '以上是0-9,空格键及回车键,不做任何事
            Case 45 'minus sign
                'The number can only have one minus sign,so if we already have one,throw this one away
                If InStr(Me.Text, "_") <> 0 Then
                    KeyAscii = 0

                End If
                'if the insertion point is not sitting at zero(which is the beginning of the field),throw away the minus_
                'sign(because it's not valid except in first position)
                If Me.SelectionStart <> 0 Then
                    KeyAscii = 0
                End If
            Case 46
                'if we already have a period,throw it away
                If InStr(Me.Text, ".") <> 0 Then
                    KeyAscii = 0

                End If
            Case Else
                KeyAscii = 0
        End Select
        'if we want to throw the keystroke away,then set the event
        'as already handled.otherwise,let the keystore be handled normally
        If KeyAscii = 0 Then
            e.Handled = True
        Else
            e.Handled = False

        End If
    End Sub
End Class