设有如下通用过程: Public Function Fun(xStr AsString)As String Dim tStr As String , strL As Integer tStr = "" strL = Len(xStr) i = 1 Do While i< = strL / 2 tStr = tStr& Mid(xStr,i,1)& Mid(xStr,strL - i + 1,1) i = i + 1 Loop Fun = tStr End Function 在窗体上画一个名称为 Command1 的命令按钮。然后编写如下的事件过程: Private Sub Command1_Click() Dim S1 As String S1 = "abcdef" Print UCase(Fun(S1)) End Sub 程序运行后,单击命令按钮,输出结果是 ( )