C#

public Form1()
{
    InitializeComponent();

    //authenticate
    SpreadsheetsService wsService = new SpreadsheetsService("testApp");
    wsService.setUserCredentials("email@gmail.com", "password");

    //retrieve available spreadsheets
    SpreadsheetQuery query = new SpreadsheetQuery();
    SpreadsheetFeed feed = wsService.Query(query);

    foreach (SpreadsheetEntry entry in feed.Entries)
    {
        comboBox1.Items.Add(entry.Title.Text.ToString());
    }
}

private void button1_Click(object sender, EventArgs e)
{
    int sheetIndex = comboBox1.SelectedIndex;

    SpreadsheetsService wsService = new SpreadsheetsService("testApp");
    wsService.setUserCredentials("email@gmail.com", "password");

    SpreadsheetQuery query = new SpreadsheetQuery();
    SpreadsheetFeed feed = wsService.Query(query);

    //retrieve the worksheets of a particular spreadsheet
    SpreadsheetEntry mySpreadsheet = (SpreadsheetEntry)feed.Entries[sheetIndex];
    AtomLink link = mySpreadsheet.Links.FindService(GDataSpreadsheetsNameTable.WorksheetRel, null);

    WorksheetQuery wQuery = new WorksheetQuery(link.HRef.ToString());
    WorksheetFeed wFeed = wsService.Query(wQuery);

    //retrieve the cells in a worksheet
    WorksheetEntry worksheetEntry = (WorksheetEntry)wFeed.Entries[0];
    AtomLink cLink = worksheetEntry.Links.FindService(GDataSpreadsheetsNameTable.CellRel, null);

    CellQuery cQuery = new CellQuery(cLink.HRef.ToString());
    CellFeed cFeed = wsService.Query(cQuery);

    foreach (CellEntry curCell in cFeed.Entries)
    {
        Debug.WriteLine("The value on row {0} and column {1} is {2}", curCell.Cell.Row,
        curCell.Cell.Column, curCell.Cell.Value);
    }
}

public class Property
{
  public string property { get; set; }
  public string value { get; set; }

  public Property() { }

  public Property(string prop, string val)
  {
    property = property;
    value = value;
  }
}

public class clsContacts
{
  public List<Property> properties { get; set; }
}

Property p = new Property();
p.property = "email";
p.value = "xxxxxxxxxxx@Acme1.net";

clsContacts lstContacts = new clsContacts();

lstContacts.properties.Add(p);

Excel._Workbook oWB;
Excel.Range oRange;
Excel._Chart oChart;

//Add a Chart for the selected data.
oWB = (Excel._Workbook)oWS.Parent;
oChart = (Excel._Chart)oWB.Charts.Add(Missing.Value, Missing.Value,
    Missing.Value, Missing.Value);
oChart.HasTitle = true;
oChart.ChartTitle.Text = "IDcsacsa\t" + "TIMEfsafafas\t" + "FASvsdvfsd";

//Use the ChartWizard to create a new chart from the selected data.
oRange = oWS.get_Range("B2", "B6");

oChart.SetSourceData(oRange, Missing.Value);
//oChart.SetSourceData(oRange1, Missing.Value);
oChart.ChartType = Microsoft.Office.Interop.Excel.XlChartType.xlLine;