In this article I will explain with an example, how to download CSV document from Database in ASP.Net Core (.Net Core 8).
Note: For beginners in ASP.Net MVC Core (.Net Core 8), please refer my article ASP.Net Core 8: Hello World Tutorial with Sample Program example.
 
 

Database

I have made use of the following table tblFiles with the schema as follow.
ASP.Net Core: Download CSV file from Database
I have already inserted few records in the table.
ASP.Net Core: Download CSV file from Database
 
Note: You can download the database table SQL by clicking the download link below.
            Download SQL file
 
 

Model

The Model class consists of the following properties.
public class FileModel
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string ContentType { get; set; }
    public byte[] Data { get; set; }
}
 
 

Database Context

The very first step is to create Database Context class.
Note: For beginners in Entity Framework, please refer my article .Net Core 8: Entity Framework with Existing Database. It covers all the information needed for connecting Entity Framework.
 
Inside the class, first inherit the EntityFrameworkCore namespace and then inherit the DbContext class.
Then using Dependency Injection, a Constructor is created DbContextOptions are passed as parameter and also the Constructor of base class i.e. DbContext class is inherited.
A DbSet Collection property of FileModel Entity is created, which will be later used for holding the Data fetched from SQL Server Database Table.
using Download_CSV_Database_Core.Models;
using Microsoft.EntityFrameworkCore;
 
namespace Download_CSV_Database_Core
{
    public class DBCtx : DbContext
    {
        public DBCtx(DbContextOptions<DBCtx> options) : base(options)
        {
        }
 
        public DbSet<FileModel> tblFIles { get; set; }
    }
}
 
 

Controller

The Controller consists of following Action methods.

Action method for handling GET operation

Inside this Action method, the records are fetched from the tblFiles Table using Entity Framework and returned to the View.
 

Action method for handling POST operation

This Action method is executed when the Download Button is clicked.
Inside this Action method, fileId is received as parameter and the records are fetched from tblFiles Table using Entity Framework based on the fileId.
Finally, the file is downloaded using File Function.
public class HomeController : Controller
{
    private DBCtx Context { get; }
    public HomeController(DBCtx _context)
    {
        this.Context = _context;
    }
 
    public IActionResult Index()
    {
        return View(this.Context.tblFIles.ToList());
    }
 
    [HttpPost]
    public IActionResult DownloadFile(int? fileId)
    {
        FileModel file = this.Context.tblFIles.Where(f => f.Id == fileId).FirstOrDefault();
        return File(file.Data, file.ContentType, file.Name);
    }
}
 
 

View

HTML Markup

Inside the View, in the very first line the FileModel is declared as IEnumerable which specifies that it will be available as a Collection.
asp--action – Name of the Action. In this case the name is DownloadFile.
asp-controller – Name of the Controller. In this case the name is Home.
method – It specifies the Form Method i.e. GET or POST. In this case it will be set to POST.
 

Form for Downloading the File

The Form consists of an HTML HiddenField and a Hidden Submit Button.
When any Download Link inside the HTML Table (Grid) is clicked, then the DownloadFile JavaScript function is called, which sets the FileId into the HiddenField and calls the click event of the Submit button which submits the Form.
When the Form is submitted, the DownloadFile Action method is called, which performs the File download operation.
 

Displaying the Files

For displaying the records, an HTML Table is used. A FOR EACH loop will be executed over the Model which will generate the HTML Table rows with the tblFiles records.
@using Download_CSV_Database_Core.Models
@model IEnumerable<FileModel>
@addTagHelper*, Microsoft.AspNetCore.Mvc.TagHelpers
@{
    Layout = null;
}
 
<!DOCTYPE html>
 
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <form method="post" asp-action="DownloadFile" asp-controller="Home">
        <input type="hidden" id="hfFileId" name="FileId" />
        <input type="submit" id="btnDownload" value="Download" style="display:none" />
    </form>
    <table border="0" cellpadding="0" cellspacing="0">
       <tr>
          <th style="width:120px">File Name</th>
          <th style="width:80px"></th>
      </tr>
      @foreach (var file in Model)
      {
          <tr>
              <td>@file.Name</td>
              <td><a href="javascript:;" onclick="DownloadFile(@file.Id)">Download</a></td>
         </tr>
      }
      </table>
      <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>
      <script type="text/javascript">
          function DownloadFile(fileId) {
              $("#hfFileId").val(fileId);
              $("#btnDownload")[0].click();
          };
      </script>
</body>
</html>
 
 

Screenshot

ASP.Net Core: Download CSV file from Database
 
 

Downloads

Download Code