Private Sub Chart1_Load(ByVal sender As _ System.Object, ByVal e As System.EventArgs) Handles Chart1.Load 'x轴上每隔5点显示时间 Chart1.AxisX.Step = 5 '每个点之间用5象素间隔 Chart1.AxisX.PixPerUnit = 5 '使图表可以滚动 Chart1.Scrollable = True '打开和关闭通讯管道 Chart1.OpenData(COD.Values, 1, COD.Unknown) Chart1.CloseData(COD.Values) End Sub 给当前的窗体添加一个叫做StockQuote的类。StockQuote类调用前面的Web服务并用返回的股票价格来更新图表。
Public Class StockQuote '组件中图形的数量 Const NUM_SERIES = 1
Private lastPoint As Integer = 0 Dim stockPrice As Single
Private pStockSymbol As String Private pStockSeries As Integer = 0 Private pChartControl As Chart
WriteOnly Property StockSymbol() Set(ByVal Value) pStockSymbol = Value End Set End Property
WriteOnly Property ChartControl() Set(ByVal Value) pChartControl = Value End Set End Property
Public Sub InvokeWebService() Dim ws As New StockWS.Service1
For i As Integer = 0 To 10000 stockPrice = ws.getPrice(pStockSymbol) pChartControl.Invoke(New _ myDelegate(AddressOf updateChart), New Object() {}) '继续之前等待1秒钟 Thread.Sleep(1000) Next End Sub
Public Delegate Sub myDelegate() Public Sub updateChart() pChartControl.OpenData(COD.Values, NUM_SERIES, COD.Unknown) pChartControl.Value(pStockSeries, lastPoint) = stockPrice '显示x轴上的时间 pChartControl.AxisX.Label(lastPoint) = DateTime.Now.ToShortTimeString lastPoint += 1 pChartControl.CloseData(COD.Values) '把滚动条移到最右边 pChartControl.AxisX.ScrollPosition = pChartControl.AxisX.ScrollSize End Sub
End Class 你通过StockSymbol属性把需要的股票编码传递给StockQuote类，并使用ChartControl属性设置图表更新。InvokeWebService()方法在循环（示例中设置为10,000）中周期性地调用上面的Web服务。由于这个类会在一个单独的线程中执行，你必须非常小心以确保自己不会自动地更新某个Windows控件，因为Windows控件并不是线程安全的（thread-safe）。作为代替，你必须使用委托并调用自己希望更新的控件上的Invoke()方法。代码每秒钟调用Web服务一次，这是由Thread.Sleep(1000)语句设置的。
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