设置TeeChart的提示文本

　　使用第三方Steema的TeeChart控件，设置鼠标放在某一线条点上，显示某一点的数据标签问题（虚线型十字光标基准线，放在线上显示对应点的二维坐标轴数据数据），调用InitTeeChartTipTools方法即可：

/// <summary>
/// TeeChart线条的指示工具
/// </summary>
Steema.TeeChart.Tools.CursorTool cursorTool;
/// <summary>
/// 鼠标指示显示的文本
/// </summary>
private Steema.TeeChart.Tools.Annotation annotation;
/// <summary>
/// 初始化线条的提示工具信息
/// </summary>
private void InitTeeChartTipTools(Steema.TeeChart.TChart tChart)
{
    //以线形式对标坐标轴
    cursorTool = new Steema.TeeChart.Tools.CursorTool(tChart.Chart);
    cursorTool.Style = Steema.TeeChart.Tools.CursorToolStyles.Both;
    cursorTool.Pen.Style = System.Drawing.Drawing2D.DashStyle.Dash;
    cursorTool.Pen.Color = Color.Black;
    cursorTool.FollowMouse = true;
    cursorTool.Change += CursorTool_Change;
    //设置提示文本的信息
    annotation = new Steema.TeeChart.Tools.Annotation(tChart.Chart);
    annotation.Shape.Font.Name = "Arial";
    annotation.Shape.Font.Size = ;
    annotation.Shape.Pen.Visible = true;
    annotation.Shape.Shadow.Visible = false;
    annotation.Shape.ShapeStyle = Steema.TeeChart.Drawing.TextShapeStyle.Rectangle;
    annotation.Position = Steema.TeeChart.Tools.AnnotationPositions.LeftBottom;
    annotation.TextAlign = StringAlignment.Center;

    for (int i = ; i < tChart.Series.Count; i++)
    {
        tChart.Series[i].MouseEnter += Line_MouseEnter;
        tChart.Series[i].MouseLeave += Line_MouseLeave;
    }

    tChart.MouseLeave += TChart_MouseLeave;
    tChart.MouseEnter += TChart_MouseEnter;
}

/// <summary>
/// 鼠标进入TeeChart的事件
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void TChart_MouseEnter(object sender, EventArgs e)
{
    cursorTool.Chart=tChartCurve.Chart;
}

/// <summary>
/// 鼠标离开TeeChart的事件
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void TChart_MouseLeave(object sender, EventArgs e)
{
    cursorTool.Chart = null;
}

/// <summary>
/// 当鼠标进入线条时，将TeeChart的cursorTool工具指示的线条设置为对应的线条
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void Line_MouseEnter(object sender, EventArgs e)
{
    cursorTool.Series = sender as Steema.TeeChart.Styles.Series;
}

/// <summary>
/// 当鼠标离开线条时，将TeeChart的cursorTool工具指示的线条设置为null
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void Line_MouseLeave(object sender, EventArgs e)
{
    cursorTool.Series = null;
}
/// <summary>
/// 鼠标指示工具改变事件
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void CursorTool_Change(object sender, Steema.TeeChart.Tools.CursorChangeEventArgs e)
{
    try
    {
        Steema.TeeChart.Tools.CursorTool cursor = sender as Steema.TeeChart.Tools.CursorTool;
        if (cursor != null && cursor.Series != null)
        {
            annotation.Text = string.Format("({0}，{1})", cursor.XValue.ToString("f1"), cursor.YValue.ToString("f1"));
            annotation.Top = cursor.Series.GetVertAxis.CalcYPosValue(InterpolateLineSeries(cursor.Series, cursor.XValue));
            annotation.Left = tChartCurve.Axes.Bottom.CalcXPosValue(cursor.XValue);
            annotation.Top -= ;//将文本放在鼠标上方
            SizeF size = this.CreateGraphics().MeasureString(annotation.Text,
                new Font(annotation.Shape.Font.Name, annotation.Shape.Font.Size));
            if (annotation.Left + size.Width +  >= annotation.Chart.Width)
            {
                annotation.Left -= (int)size.Width + ;//防止文本标签超出右边界而看不全
            }
        }
        else
        {
            //将其设置到控件外部
            annotation.Text = "";
            annotation.Top = annotation.Chart.Height + ;
            annotation.Left = annotation.Chart.Width + ;
        }
    }
    catch (Exception ex)
    {
        annotation.Text = ex.Message;
        annotation.Top = ;
        annotation.Left = ;
    }
}
/// <summary>
/// 计算某一点的Y值坐标
/// </summary>
/// <param name="series">曲线</param>
/// <param name="xvalue">对应的X轴的值</param>
/// <returns>计算得到的对应的Y轴的值</returns>
private double InterpolateLineSeries(Steema.TeeChart.Styles.Series series, double xvalue)
{
    try
    {
        int index;
        for (index = series.FirstVisibleIndex; index <= series.LastVisibleIndex; index++)
        {
            if (index == - || series.XValues.Value[index] > xvalue) break;
        }
        // safeguard
        if (index < )
        {
            index = ;
        }
        else if (index >= series.Count)
        {
            index = series.Count - ;
        }
        // y=(y2-y1)/(x2-x1)*(x-x1)+y1
        double dx = series.XValues[index] - series.XValues[index - ];
        double dy = series.YValues[index] - series.YValues[index - ];
        if (dx != 0.0)
        {
            return dy * (xvalue - series.XValues[index - ]) / dx + series.YValues[index - ];
        }
        else
        {
            return 0.0;
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
        return 0.0;
    }
}