通过继承TextBox，添加了一个ValidText属性，用来获取和设置有效的文本输入

还有一个EditAble属性，决定文本框是否支持退格编辑。

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Public Class MyTextBox
Inherits System.Windows.Forms.TextBox
Private m_strValidText As String = "0123456789.+-" & Chr(13).ToString
Private m_blnEditable As Boolean = True

#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()
components = New System.ComponentModel.Container
End Sub

#End Region

Private Sub MyTextBox_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles MyBase.KeyPress
Dim strLocalString As String
If EditAble Then
strLocalString = m_strValidText & Chr(8).ToString
Else
strLocalString = m_strValidText
End If
If UCase(strLocalString).IndexOf(UCase(e.KeyChar)) < 0 Then
e.Handled = True
Beep()
Else

End If
End Sub
Public Property ValidText() As String
Get
Return m_strValidText
End Get
Set(ByVal Value As String)
m_strValidText = Value
End Set
End Property
Public Property EditAble() As Boolean
Get
Return m_blnEditable
End Get
Set(ByVal Value As Boolean)
m_blnEditable = Value
End Set
End Property
End Class