主题：【求助】清除所有控件时的清除按钮出错

For Each c As WinForm.Control In e.Form.Controls
        If Typeof c Is winform.TextBox OrElse TypeOf c Is winform.Combobox OrElse TypeOf c Is winform.DropDownBox Then
            Dim t As WinForm.TextBox = c
            Dim t1 As WinForm.Combobox = c
            Dim t2 As WinForm.DropDownBox = c
            t.Value = Nothing
            t1.Value = Nothing
            t2.Value = Nothing
        End If
    Next

此主题相关图片如下：qq图片20180507143819.png