How to Efficiently Return Files for Viewing or Downloading in ASP.NET MVC?

Streamlining File Downloads and Views in ASP.NET MVC

Handling file downloads and previews within ASP.NET MVC applications can present complexities. This article explores effective strategies for returning files stored in a database, offering a robust solution to overcome common hurdles.

The FileStreamResult approach, while functional for many file types, falls short when dealing with unknown extensions or requiring forced downloads. Using FileDownloadName forces a download, bypassing the browser's automatic handling.

A superior solution utilizes the ContentDispositionHeaderValue class (in modern ASP.NET MVC versions) to precisely control file behavior. This allows developers to specify whether a file should be displayed inline or downloaded directly.

Here's an example using ASP.NET Core:

<code class="language-csharp">public IActionResult Download()
{
    Document document = ... // Retrieve document from database

    var cd = new ContentDispositionHeaderValue("attachment")
    {
        FileNameStar = document.FileName
    };
    Response.Headers.Add(HeaderNames.ContentDisposition, cd.ToString());

    return File(document.Data, document.ContentType);
}</code>

By manipulating FileNameStar and related properties, you gain fine-grained control over inline viewing versus download prompts. This method also gracefully handles filenames containing international characters.

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