How to update Series.values in C#?

Question

I have an issue with the excel , please let me help how can i solve it. Below is the code which is i'm using now , but its not working .

at last side code series.values should update excel file as recently updated , so how can i use it. i'm doing this to increase the chart range.

 

Excel.Application app = new Excel.Application();

// Excel.Application xlApp;

Excel.Workbook xlWorkBook;

Excel._Worksheet sheet;

Excel.ChartObject chartObj;

Excel._Chart chart;

Excel.Series series;

object useDefault = Type.Missing;

Excel.Workbook book;

Excel.ChartObjects grph;

xlWorkBook = app.Workbooks.Open(@"E:\\test\\DTS-CODE");//Open the work book

sheet = xlWorkBook.Sheets["Trend_NCM"];//Select the sheet the chart is on

char oldformula , newformula;

long i, s;

Excel.Range orng = null;

string[] stmp, sbase;

string cha, rta;

string startingpoint, endpoint;

chart = sheet.ChartObjects("Chart 1").chart;

chart.SetSourceData(sheet.Range["A2:A7"], Excel.XlRowCol.xlRows);

for (s = 1; s < chart.SeriesCollection().count;s++)

{

string sting = "=SERIES(Trend_NCM!$A$3,Trend_NCM!$B$2:$AH$2,Trend_NCM!$B$3:$AH$3,1)";

//series.Values

rta = chart.SeriesCollection(s).Formula;

// foreach(sbase in chart.SeriesCollection().count)

//series = rta.Chart.SeriesCollection();

// series = chart.SeriesCollection(s).Formula;

series= null ;

cha = chart.SeriesCollection(s).Formula;

string[] cha1 = cha.Split(',');

string[] cha2 = cha1[2].Split(':');

startingpoint = cha2[0];

//endpoint = cha2[1];

Range xlrange = null;

Excel.Range last = sheet.Cells.SpecialCells(Excel.XlCellType.xlCellTypeLastCell, Type.Missing);

Excel.Range range = sheet.get_Range("A1", last);

int iTotalColumns = sheet.UsedRange.Columns.Count;

// Excel.Range xlRange = sheet.UsedRange;

// xlrange = sheet.get_Range(xlrange.EntireRow.Address, useDefault);

// endpoint = iTotalColumns.ToString();

endpoint = "Trend_NCM!$AH$5";

**series.Values = startingpoint+ "&"+ ":" +"&"+ endpoint;**

}