1、安装引用DotNetCore.NPOI
1）使用Nuget界面管理器
搜索"DotNetCore.NPOI",在列表中找到它，点击"安装"
相关文档：VS(Visual Studio)中Nuget的使用
2）使用Package Manager命令安装
PM> Install-Package DotNetCore.NPOI
3）使用.NET CLI命令安装
> dotnet add TodoApi.csproj package DotNetCore.NPOI
2、使用NPOI设置Excel的单元格背景颜色
命名空间：
using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
示例代码：
IWorkbook workbook = new XSSFWorkbook();ISheet sheet = workbook.GetSheet("Sheet1");IRow row = sheet.CreateRow(0);//stylingIFont boldFont = workbook.CreateFont();boldFont.Boldweight = (short)FontBoldWeight.Bold;ICellStyle boldStyle = workbook.CreateCellStyle();boldStyle.SetFont(boldFont);boldStyle.BorderBottom = BorderStyle.Medium;boldStyle.FillForegroundColor = NPOI.HSSF.Util.HSSFColor.Grey25Percent.Index;boldStyle.FillPattern = FillPattern.SolidForeground;ICell cell = row.CreateCell(5);cell.SetCellValue("wonhero");cell.CellStyle = boldStyle;