How to Add Watermark to Excel Worksheets using C#. For more information, please follow link: https://kb.groupdocs.com/annotation/net/how-to-add-watermark-to-excel-worksheets-using-csharp/

How to Add Watermark to Excel Worksheets using C#.cs

using System;
using GroupDocs.Annotation;
using GroupDocs.Annotation.Models;
using GroupDocs.Annotation.Models.AnnotationModels;

namespace AddWatermarktoExcelUsingCSharp
{
    internal class Program
    {
        static void Main(string[] args)
        {
            // Set License to avoid the limitations of Annotation library
            License lic = new License();
            lic.SetLicense(@"GroupDocs.Annotator.lic");

            //Instantiate Annotator object and pass input Excel document
            using (Annotator annotatorXLSX = new Annotator("input.xlsx"))
            {
                //Instantiate WatermarkAnnotation object and set it's properties
                WatermarkAnnotation watermarkExcel = new WatermarkAnnotation
                {
                    Angle = 45,
                    Box = new Rectangle(200, 200, 100, 50),
                    CreatedOn = DateTime.Now,
                    Text = "Watermark",
                    FontColor = 65535,
                    FontSize = 36,
                    Message = "This is watermark annotation in Excel document",
                    Opacity = 0.7,
                    AutoScale = true,
                    HorizontalAlignment = HorizontalAlignment.Center,
                    VerticalAlignment = VerticalAlignment.Center
                };

                //Add Watermark in Excel document
                annotatorXLSX.Add(watermarkExcel);
                //Save the final Excel XLSX
                annotatorXLSX.Save("result.xlsx");
            }
        }
    }
}