IP地址输入控件 V1.0.1.1版(FOR Win Form)

核心代码:

 '只允许输入数字、"."
    Private Sub txtField_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtField0.KeyPress, txtField1.KeyPress, txtField2.KeyPress, txtField3.KeyPress
        If e.KeyChar = "." Then
            Dim tx As TextBox = CType(sender, TextBox)
            '最后的文本框不可以输入"."
            '在其它文本框输入"."，相当于输入"Tab"键，即光标到下一文本框
            If tx.Text = "" Or tx.SelectedText <> "" Then
                e.Handled = True
            End If
            If tx.Name <> "txtField3" Then
                SendKeys.Send("{TAB}")
            Else
                '最后的文本框不可以输入"."
                e.Handled = True
            End If
        ElseIf (Not IsNumeric(e.KeyChar)) And e.KeyChar <> ControlChars.Back Then
            e.Handled = True
        Else
            Dim tx As TextBox = CType(sender, TextBox)
            If (Len(tx.Text) = 2 And e.KeyChar <> ControlChars.Back And tx.SelectedText.Length = 0) Then
                If tx.Name <> "txtField3" Then
                    SendKeys.Send("{TAB}")
                End If
            End If
        End If
        '控制ControlChars.Back退格键
        Dim tx1 As TextBox = CType(sender, TextBox)
        If (Len(tx1.Text) = 0 And e.KeyChar = ControlChars.Back) Then
            Select Case tx1.Name
                Case "txtField3"
                    If txtField3.Text = "" Then
                        txtField2.Focus()
                    End If
                Case "txtField2"
                    If txtField2.Text = "" Then
                        txtField1.Focus()
                    End If
                Case "txtField1"
                    If txtField1.Text = "" Then
                        txtField0.Focus()
                    End If
            End Select
        End If
    End Sub

当运行时：



当出现错误时：