通過繼承TextBox，添加了一個ValidText屬性，用來獲取和設置有效的文本輸入

還有一個EditAble屬性，決定文本框是否支持退格編輯。

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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 窗體設計器生成的代碼 "

Public Sub New()
MyBase.New()
'該調用是 Windows 窗體設計器所必需的。
InitializeComponent()

'在 InitializeComponent() 調用之后添加任何初始化

End Sub

'UserControl1 重寫 dispose 以清理組件列表。
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 窗體設計器所必需的
Private components As System.ComponentModel.IContainer

'注意: 以下過程是 Windows 窗體設計器所必需的
'可以使用 Windows 窗體設計器修改此過程。
'不要使用代碼編輯器修改它。
<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