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创建Excel的示例代码

命名空间：

using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
using System;
using System.Data;
using System.IO;

示例代码：

public static void TransferXLToTable()
{
    DataTable dt = new DataTable();
    dt.Columns.Add("City", typeof(string));
    dt.Columns.Add("State", typeof(string));
    dt.Columns.Add("Zip", typeof(string));
    //
    using (FileStream stream = new FileStream(@"C:\Working\source.xlsx",
                                              FileMode.Open,
                                              FileAccess.Read))
    {
        IWorkbook wb = new XSSFWorkbook(stream);
        ISheet sheet = wb.GetSheet("Sheet1");
        string holder;
        int i = 0;
        do
        {
            DataRow dr = dt.NewRow();
            IRow row = sheet.GetRow(i);
            try
            {
                holder = row.GetCell(0, MissingCellPolicy.CREATE_NULL_AS_BLANK).ToString();
            }
            catch (Exception)
            {
                break;
            }
            string city = holder.Substring(0, holder.IndexOf(','));
            string state = holder.Substring(holder.IndexOf(',') + 2, 2);
            string zip = holder.Substring(holder.IndexOf(',') + 5, 5);
            dr[0] = city;
            dr[1] = state;
            dr[2] = zip;
            dt.Rows.Add(dr);
            i++;
        } while (!String.IsNullOrEmpty(holder));
    }
    using (FileStream stream = new FileStream(@"C:\Working\FieldedAddresses.xlsx", FileMode.Create, FileAccess.Write))
    {
        IWorkbook wb = new XSSFWorkbook();
        ISheet sheet = wb.CreateSheet("Sheet1");
        ICreationHelper cH = wb.GetCreationHelper();
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            IRow row = sheet.CreateRow(i);
            for (int j = 0; j < 3; j++)
            {
                ICell cell = row.CreateCell(j);
                cell.SetCellValue(cH.CreateRichTextString(dt.Rows[i].ItemArray[j].ToString()));
            }
        }
        wb.Write(stream);
    }
}
    var demoService = provider.GetRequiredService<DemoService>();
    Console.WriteLine($"Output: {demoService.HelloWorld()}");
    Console.ReadKey();
}

文档：https://github.com/dotnetcore/NPOI