In this article I will explain with an example, how to upload files, save (insert) file to Database Table, retrieve (display) files in HTML Grid and download the files from Database Table in ASP.Net Core MVC.
 
 
Database
This article makes use of a table named tblFiles whose schema is defined as follows.
ASP.Net Core MVC: Upload Files, Save (Insert) file to Database and Download Files
 
Note: You can download the database table SQL by clicking the download link below.
          Download SQL file
 
 
Namespaces
You will need to import the following namespaces.
using System.IO;
using System.Data.SqlClient;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
 
 
Model
The following Model class consists of the following properties needed for inserting and populating the records of the Files from database.
public class FileModel
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string ContentType { get; set; }
    public byte[] Data { get; set; }
}
 
 
Controller
The Controller consists of three Action methods.
Action method for handling GET operation
Inside this Action method, the GetFiles method is called.
Inside the GetFiles method, the records from the tblFiles table are fetched using DataReader and generic list of FileModel class objects is populated.
Note: For details about reading Connection String from AppSettings.json, please refer my article, .Net Core: Read Connection String from AppSettings.json file.
 
Finally, the generic list of FileModel class objects is returned to the View.
 
Action method for handling POST operation for uploading Files
This Action method gets called when a File is selected and the Upload Button is clicked, and it gets the uploaded file in the IFormFile parameter.
Note: In case the IFormFile parameter is appearing NULL, then please refer the article, ASP.Net Core: IFormFile always returns NULL.
 
The uploaded file is converted to an Array of Bytes using MemoryStream class and finally, is inserted into the database table.
After successful insert of the File, RedirectToAction is called which redirects to the Index Action method.
 
Action method for handling POST operation for downloading Files
When the Download Link inside the HTML Table (Grid) is clicked, then the ID of the particular file is sent to this Action method and using the File ID, the File’s binary data is fetched from the database.
Finally, the File is downloaded using the File function.
public class HomeController : Controller
{
    private IConfiguration Configuration;
 
    public HomeController(IConfiguration _configuration)
    {
        Configuration = _configuration;
    }
 
    public IActionResult Index()
    {
        return View(this.GetFiles());
    }
 
    [HttpPost]
    public IActionResult UploadFile(IFormFile postedFile)
    {
        string fileName = Path.GetFileName(postedFile.FileName);
        string contentType = postedFile.ContentType;
        using (MemoryStream ms = new MemoryStream())
        {
            postedFile.CopyTo(ms);
            string constr = this.Configuration.GetConnectionString("MyConn");
            using (SqlConnection con = new SqlConnection(constr))
            {
                string query = "INSERT INTO tblFiles VALUES (@Name, @ContentType, @Data)";
                using (SqlCommand cmd = new SqlCommand(query))
                {
                    cmd.Connection = con;
                    cmd.Parameters.AddWithValue("@Name", fileName);
                    cmd.Parameters.AddWithValue("@ContentType", contentType);
                    cmd.Parameters.AddWithValue("@Data", ms.ToArray());
                    con.Open();
                    cmd.ExecuteNonQuery();
                    con.Close();
                }
            }
        }
 
        return RedirectToAction("Index");
    }
 
    [HttpPost]
    public IActionResult DownloadFile(int fileId)
    {
        byte[] bytes;
        string fileName, contentType;
        string constr = this.Configuration.GetConnectionString("MyConn");
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand())
            {
                cmd.CommandText = "SELECT Name, Data, ContentType FROM tblFiles WHERE Id=@Id";
                cmd.Parameters.AddWithValue("@Id", fileId);
                cmd.Connection = con;
                con.Open();
                using (SqlDataReader sdr = cmd.ExecuteReader())
                {
                    sdr.Read();
                    bytes = (byte[])sdr["Data"];
                    contentType = sdr["ContentType"].ToString();
                    fileName = sdr["Name"].ToString();
                }
                con.Close();
            }
        }
 
        return File(bytes, contentType, fileName);
    }
 
    private List<FileModel> GetFiles()
    {
        List<FileModel> files = new List<FileModel>();
        string constr = this.Configuration.GetConnectionString("MyConn");
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT Id, Name FROM tblFiles"))
            {
                cmd.Connection = con;
                con.Open();
                using (SqlDataReader sdr = cmd.ExecuteReader())
                {
                    while (sdr.Read())
                    {
                        files.Add(new FileModel
                        {
                            Id = Convert.ToInt32(sdr["Id"]),
                            Name = sdr["Name"].ToString()
                        });
                    }
                }
                con.Close();
            }
        }
        return files;
    }
}
 
 
View
Inside the View, in the very first line the FileModel class is declared as IEnumerable which specifies that it will be available as a Collection.
The View consists of two HTML Forms which have been created using the ASP.Net Tag Helpers attributes.
asp-action – Name of the Action.
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.
 
Uploading the File
The Form consists of an HTML FileUpload and a Submit Button.
When the Submit Button is clicked, the UploadFile Action method for handling POST operation will be called.
 
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 ultimately 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 files, an HTML Table is used. A loop will be executed over the Model which will generate the HTML Table rows with the File records.
@addTagHelper*, Microsoft.AspNetCore.Mvc.TagHelpers
@model IEnumerable<Upload_File_Database_MVC_Core.Models.FileModel>
@{
    Layout = null;
}
 
<!DOCTYPE html>
 
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
    <style type="text/css">
        body { font-family: Arial; font-size: 10pt; }
        table { border: 1px solid #ccc; border-collapse: collapse; background-color: #fff; }
        table th { background-color: #B8DBFD; color: #333; font-weight: bold; }
        table th, table td { padding: 5px; border: 1px solid #ccc; }
        table, table table td { border: 0px solid #ccc; }
    </style>
</head>
<body>
    <form method="post" enctype="multipart/form-data" asp-controller="Home" asp-action="UploadFile">
        <input type="file" name="postedFile" />
        <input type="submit" id="btnUpload" value="Upload" />
    </form>
    <form method="post" asp-controller="Home" asp-action="DownloadFile">
        <input type="hidden" id="hfFileId" name="FileId" />
        <input type="submit" id="btnDownload" value="Download" style="display:none" />
    </form>
    <hr/>
    <table id="tblFiles" cellpadding="0" cellspacing="0">
        <tr>
            <th style="width:50px">File ID</th>
            <th style="width:120px">File Name</th>
            <th style="width:80px">Download</th>
        </tr>
        @foreach (var file in Model)
        {
            <tr>
                <td>@file.Id</td>
                <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/1.8.3/jquery.min.js"></script>
    <script type="text/javascript">
        function DownloadFile(fileId) {
            $("#hfFileId").val(fileId);
            $("#btnDownload")[0].click();
        };
    </script>
</body>
</html>
 
 
Screenshot
ASP.Net Core MVC: Upload Files, Save (Insert) file to Database and Download Files
 
 
Downloads
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