textbox扫描枪扫后自动全选中


在TxtNameCode_TextChanged下加了如下代码:

Private Sub TxtNameCode_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TxtNameCode.TextChanged
TxtNameCode.SelectAll()
End Sub

结果变成一位空格选中了:


请问如何解决这个问题?
[解决办法]
扫描枪模拟的是SendKeys
你每次全选字符，每次都会被覆盖

好的办法是当扫描枪将最后一个键(回车键)时全选

    Private Sub TextBox1_KeyUp(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyUp
        Select Case e.KeyCode
            Case Keys.Enter
                TextBox1.SelectAll()
        End Select
    End Sub