How to return an Excel file from ASP.NET Core Web API web-app?

Question

In similar questions, with this code works to download a PDF:

I\'m testing with local files (.xlsx, .pdf, .zip) inside the Controller folder.

Answer 1

you can use NPOI

using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using NPOI.SS.UserModel;
using NPOI.SS.Util;
using NPOI.XSSF.UserModel;
using System.Collections.Generic;
using System.IO;

namespace export_excel.Controllers
{

    [ApiController]
    [Route("[controller]")]
    public class ExportExcelController : ControllerBase
    {

        private readonly IHostingEnvironment _hostingEnvironment;

        public ExportExcelController(IHostingEnvironment hostingEnvironment)
        {
            _hostingEnvironment = hostingEnvironment;
        }

        // https://localhost:5001/ExportExcel/Export
        // https://localhost:5001/static-file/employee.xlsx
        [HttpGet]
        [Route("Export")]
        public IActionResult Export()
        {
            List list = new List()
            {
                new Employee{ emp_code = "152110032", Name = "Nguyen Hong Anh", Phone = "0909998789" },
                new Employee{ emp_code = "152110055", Name = "Tran Phuong Dung", Phone = "0909993456" },
                new Employee{ emp_code = "152110022", Name = "Do Bich Ngoc", Phone = "0909991237" },
                new Employee{ emp_code = "152110025", Name = "Tran Thu Ha", Phone = "0909990987" },
            };
            // New workbook.
            XSSFWorkbook wb = new XSSFWorkbook();
            // New worksheet.
            ISheet sheet = wb.CreateSheet();
            // Write to sheet.
            // Tạo row
            var row0 = sheet.CreateRow(0);
            // At first row, merge 3 columns.
            // Create cell before merging.
            row0.CreateCell(0);
            CellRangeAddress cellMerge = new CellRangeAddress(0, 0, 0, 2);
            sheet.AddMergedRegion(cellMerge);
            row0.GetCell(0).SetCellValue("Employee information");
            // Ghi tên cột ở row 1
            var row1 = sheet.CreateRow(1);
            row1.CreateCell(0).SetCellValue("emp_code");
            row1.CreateCell(1).SetCellValue("fullname");
            row1.CreateCell(2).SetCellValue("Phone");
            // Traversaling array, then write continous.
            int rowIndex = 2;
            foreach (var item in list)
            {
                // Init new row.
                var newRow = sheet.CreateRow(rowIndex);
                // set values.
                newRow.CreateCell(0).SetCellValue(item.emp_code);
                newRow.CreateCell(1).SetCellValue(item.Name);
                newRow.CreateCell(2).SetCellValue(item.Phone);
                // Increase index.
                rowIndex++;
            };
            if (!System.IO.File.Exists("c:\\myfiles\\employee.xlsx"))

            {
                FileStream fs = new FileStream(@"c:\myfiles\employee.xlsx", FileMode.CreateNew);
                wb.Write(fs);
            }
            var path = Path.Combine(@"c:\myfiles\employee.xlsx");
            return File(System.IO.File.OpenRead(path), contentType: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet; charset=utf-8", fileDownloadName: "employee.xlsx");
        }

    }

    public class Employee
    {
        public string emp_code;
        public string Name;
        public string Phone;
    }

}

File Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.FileProviders;
using Microsoft.Extensions.Hosting;
using System.IO;

namespace export_excel
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            app.UseHttpsRedirection();
            app.UseRouting();
            app.UseAuthorization();
            app.UseStaticFiles(new StaticFileOptions
            {
                FileProvider = new PhysicalFileProvider(
            // Path.Combine(env.ContentRootPath, @"c:\audio\")),
            // Path.Combine(@"c:\audio\")),
            Path.Combine(@"c:\myfiles")),
                RequestPath = "/static-file"
            });
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }

}

You can use 1 of 2 ways, go to

https://localhost:5001/ExportExcel/Export

or

https://localhost:5001/static-file/employee.xlsx