public class ContourSeries : SurfaceSeries 

var workbook = Workbook.Create( ChartSample.ChartSampleOutputDirectory + @"AddCharts.xlsx" );

// Gets the first Worksheet. A Workbook always contains at least 1 Worksheet.
var worksheet = workbook.Worksheets[ 0 ];

// Adds Values for Category.
worksheet.Cells[ "B4" ].Value = 2020;
worksheet.Cells[ "B5" ].Value = 2021;
worksheet.Cells[ "B6" ].Value = 2022;
worksheet.Cells[ "B7" ].Value = 2023;
worksheet.Cells[ "B8" ].Value = 2024;

// Adds Values for Series.
worksheet.Cells[ "C4" ].Value = 20d;
worksheet.Cells[ "C5" ].Value = 28d;
worksheet.Cells[ "C6" ].Value = 33d;
worksheet.Cells[ "C7" ].Value = 12d;
worksheet.Cells[ "C8" ].Value = 45d;

// Adds a Contour3DChart with the generic Add method and set its SubType. The size of the Chart will be from Cell E4 to L18.
var contour3DChart = worksheet.Charts.Add<Contour3DChart>( "E4", "L18" );
contour3DChart.SubType = Contour3DChartSubType.Contour;

// Sets the Chart's Title.
contour3DChart.Title.Text = "Profits";
contour3DChart.Title.TextOptions.Font.Bold = true;

// Sets the Legend.
contour3DChart.Legend.Position = LegendPositionType.Right;

// Sets the Category data(x values) for the Contour3DChart : Cells B4 to B8.
contour3DChart.CategoryData = CategoryData.FromCells( worksheet, "B4", "B8" );

// Adds ContourSeries to the Contour3DChart (y values) by specifying fixed values and a range of Cells’ Adresses.
var contourSeries1 = contour3DChart.SeriesCollection.AddFromValues<ContourSeries>( 5d, 10d, 15d, 20d, 40d );
contourSeries1.Name = "IBM";
var contourSeries2 = contour3DChart.SeriesCollection.AddFromCells<ContourSeries>( "C4", "C8" );
contourSeries2.Name = "Apple";

// Saves Workbook to disk.
workbook.Save();