項目中要用圖形來顯示一個閥門的開度，以及控制閥的開度。本來是要用什么公司買的控件中的餅圖之類的實現，不過我覺得也是麻煩，就想，還是自己畫吧。

首先添加一個trackbar，名字是“trackbar1”，一個label，名字是“l_a_shang”，一個groupbox，名字是“gb_right”,，然后添加拉動滾動條時的處理函數

 '上位機控制
        dim m_start as integer
        dim rcdraw as system.drawing.rectangle

        private sub trackbar1_scroll(byval sender as object, byval e as system.eventargs) handles trackbar1.scroll
            m_start = (100 - trackbar1.value)
            me.l_a_shang.text = me.trackbar1.value.tostring
            gb_right.invalidate() '重畫gb_right
        end sub

添加gb_right重畫時的處理函數

 private sub gb_right_paint(byval sender as object, byval e as system.windows.forms.painteventargs) handles gb_right.paint
            rcdraw.x = trackbar1.location.x - 40
            rcdraw.y = 20
            rcdraw.height = 100
            rcdraw.width = 20
            e.graphics.drawrectangle(new pen(color.blue, 5), rcdraw)
            dim i = trackbar1.location.x - 40
            for i = trackbar1.location.x - 40 to trackbar1.location.x - 20
                e.graphics.drawline(new pen(color.blue, 5), i, m_start + 20, i, 120)
            next

             me.l_a_shang.text = me.trackbar1.value.tostring + "%"
        end sub

到此以及可以實現拉動條的時候，圖像跟著變化，并顯示百分比。