一、生成折线图方法 

/// <summary>
        ///生成折线图
        /// </summary>
        /// <param name="worksheet">sheet页数据 </param>
        /// <param name="colcount">总列数</param>
        /// <param name="tablename">table名</param>

static void CreateChart(ExcelWorksheet worksheet, int colcount, string tablename)
        {
            ExcelChart chart = worksheet.Drawings.AddChart("chart", eChartType.LineMarkers);//图表类型 Line折线图  LineMarkers点线
            chart.Legend.Position = eLegendPosition.Bottom;//图像图例定位
            //worksheet.Cells[2,2, colcount, 2]   范围表示  Cells[开始行索引,开始列索引,结束行索引,结束列索引]  
            ExcelChartSerie serie1 = chart.Series.Add(worksheet.Cells[2, 2, co