项目中要用图形来显示一个闸门的开度，以及控制闸的开度。首先添加一个trackbar，名字是“trackbar1”，一个label，名字是“l_a_shang”，一个groupBox，名字是“gb_right”,，然后添加拉动滚动条时的处理函数

上位机控制
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() 重画gb_right
end sub

添加gb_right重画时的处理函数

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,i,m_start + 20,120)
next

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

到此以及可以实现拉动条的时候，图像跟着变化，并显示百分比。