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。