代码如下：
1 Public Class NumericTextBox 2 Inherits System.Windows.Forms.TextBox 3 4 #Region " Windows Form Designer generated code " 5 6 Public Sub New() 7 MyBase.New() 8 9 'This call is required by the Windows Form Designer. 10 InitializeComponent() 11 12 'Add any initialization after the InitializeComponent() call 13 14 End Sub 15 16 'UserControl1 overrides dispose to clean up the component list. 17 Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean) 18 If disposing Then 19 If Not (components Is Nothing) Then 20 components.Dispose() 21 End If 22 End If 23 MyBase.Dispose(disposing) 24 End Sub 25 26 'Required by the Windows Form Designer 27 Private components As System.ComponentModel.IContainer 28 29 'NOTE: The following procedure is required by the Windows Form Designer 30 'It can be modified using the Windows Form Designer. 31 'Do not modify it using the code editor. 32 <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent() 33 components = New System.ComponentModel.Container() 34 End Sub 35 36 #End Region 37 38 Private Sub NumericTextBox_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles MyBase.KeyPress 39 Dim KeyAscii As Integer 40 KeyAscii = Asc(e.KeyChar) 41 42 Select Case KeyAscii 43 44 Case 48 To 57, 8, 13 ' these are the digits 0-9, backspace, 45 ' and carriage return 46 ' we're OK on these, don't do anything 47 48 Case 45 ' minus sign 49 50 ' The number can only have one minus sign, so 51 ' if we already have one, throw this one away 52 If InStr(Me.Text, "-") <> 0 Then 53 KeyAscii = 0 54 End If 55 56 ' if the insertion point is not sitting at zero 57 ' (which is the beginning of the field), throw away the minus 58 ' sign (because it's not valid except in first position) 59 If Me.SelectionStart <> 0 Then 60 KeyAscii = 0 61 End If 62 63 Case 46 ' this is a period (decimal point) 64 65 ' if we already have a period, throw it away 66 If InStr(Me.Text, ".") <> 0 Then 67 KeyAscii = 0 68 End If 69 70 Case Else 71 ' provide no handling for the other keys 72 KeyAscii = 0 73 74 End Select 75 76 ' If we want to throw the keystroke away, then set the event 77 ' as already handled. Otherwise, let the keystroke be handled normally. 78 If KeyAscii = 0 Then 79 e.Handled = True 80 Else 81 e.Handled = False 82 End If 83 84 End Sub 85 End Class
