In this article I will explain with an example, how to download file as attachment in browser in ASP.Net Core MVC.
Note: For beginners in ASP.Net Core 7, please refer my article ASP.Net Core 7: Hello World Tutorial with Sample Program example.
 
 

Location of the File

The File to be downloaded is stored in the Files Folder (Directory) inside the wwwroot Folder (Directory).
Download file as attachment in Browser in ASP.Net Core
 
 

Controller

The Controller consists of following Action methods.

Action method for handling GET operation

Inside this Action method, simply the View is returned.
 

Action method for handling POST operation

This Action method gets called, when Download button is clicked.
Inside this Action method, the path of the File to be downloaded is fetched from the wwwroot Folder (Directory) using IWebHostEnvironment interface.
Note: The IWebHostEnvironment interface is injected using Dependency Injection inside the HomeController class, for more details please refer Using IWebHostEnvironment in ASP.Net Core.
 
Then, the File is read as Binary Data into a BYTE Array using the ReadAllBytes method of the File class.
Finally, the BYTE Array is sent for download with content type as octet-stream using the File function.
Note: octet-stream is used to send any type of file in the form of BYTE array over the internet.
 
public class HomeController : Controller
{
    private IWebHostEnvironment Environment { get; set; }
 
    public HomeController(IWebHostEnvironment _environment)
    {
        this.Environment = _environment;
    }
 
    public IActionResult Index()
    {
        return View();
    }
 
    [HttpPost]
    public IActionResult Download()
    {
        //Build the File Path.
        string path = Path.Combine(this.Environment.WebRootPath, "Files\\Sample.pdf");
 
        //Read the File data into Byte Array.
        byte[] bytes = System.IO.File.ReadAllBytes(path);
 
        //Send the File to Download.
        return File(bytes, "application/octet-stream", "Sample.pdf");
    }
}
 
 

View

The View consists of an HTML Form which has been created using the ASP.Net TagHelpers with the following attributes.
asp-action – Name of the Action. In this case the name is Download.
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.
The Form consists of an HTML INPUT Submit button.
 

Submitting the Form

When the Submit button is clicked the form will be submitted to the Controller’s Action method.
@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="Download" asp-controller="Home">
        <input type="submit" value="Download" />
    </form>
</body>
</html>
 
 

Screenshot

Download file as attachment in Browser in ASP.Net Core
 
 

Demo

View Demo
 
 

Downloads

Download Code