How to download multiple files in ASP.NET Core MVC

Question

How to download multiple files? If the user sends a single file, display it, and if the user sends multiple files, how to set?

This is my controller code:

public IActionResult DownloadFile(int id)  
{  
    byte[] bytes;   
    string fileName, contentType;  
  
    var model = new List<Files>();  
  
    var getdocument = _documentdata.GetDocumentbyDocumentId(id);  
  
    if (getdocument != null)  
    {  
        fileName = getdocument.Name;  
        contentType = getdocument.FileType;  
        bytes = getdocument.DataFiles;  
  
        return File(bytes, contentType: "application/octet-stream", fileName);  
    }  
       
    return Ok("Can't find the image");  
}  

Upload is working storing in database 2 tables when I click uploaded download ?

Getting document single id

public Files GetDocumentbyDocumentId(int documentId)  
{  
    var list = (from doc in _auc.Files  
                where doc.DocumentId == documentId  
                select doc).FirstOrDefault();  
    return list;  
}  

Answer 1

Hi @selfie tv ,

How to download multiple files?

To download multiple file, you can create a zip file and add the multiple files inside it. Refer to the following sample:

In this sample, I will query the Products table and get their image content, then download them using a Zip file.

    public IActionResult DownLoadAll()  
    {  
        var zipName = $"TestFiles-{DateTime.Now.ToString("yyyy_MM_dd-HH_mm_ss")}.zip";  
        using (MemoryStream ms = new MemoryStream())  
        {  
            //required: using System.IO.Compression;  
            using (var zip = new ZipArchive(ms, ZipArchiveMode.Create, true))  
            {  
                //QUery the Products table and get all image content  
                _dbcontext.Products.ToList().ForEach(file =>  
                {  
                    var entry = zip.CreateEntry(file.ProImageName);  
                    using (var fileStream = new MemoryStream(file.ProImageContent))  
                    using (var entryStream = entry.Open())  
                    {  
                        fileStream.CopyTo(entryStream);  
                    }  
                });  
            }   
            return File( ms.ToArray(), "application/zip", zipName);   
        }  
    }  

Code in the Index page:

<a asp-controller="Product" asp-action="DownLoadAll">DownLoad All Images</a>  

Products model:

public class Product  
{  
    [Key]  
    public int ProId { get; set; }  
    public string ProName { get; set; }  
    public string ProImageName { get; set; }  
    public byte[] ProImageContent { get; set; } //Image content.  
    public string ProImageContentType { get; set; }  
    //you can add another properties  
}  

The output as below:

If the user sends a single file, display it, and if the user sends multiple files, how to set?

How do you display the files? Using a new browser tab or a web page?

If you want to display the file using the browser, you can view the single file, for the multiple file, generally it will down it via a zip file, then to view them, you can unzip the file and view them on local.

If you are display the files using a web page, in the web page, you can use a for/foreach statement to loop the files, and display them one by one.

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Best regards,
Dillion