Download file to browser using .NET Core Razor Pages

Question

Using ASP.NET Razor Pages, I am trying download a file to the browser. From the Page(html), using a link like this works fine:

href="/DownloadableFiles/testB.csv" download="newname">Download Link

However, I want to initiate the download from the code-behind or ViewModel so it can be dynamic as to what the filename is, I also need to inspect the file first, etc.

In ASP.NET MVC core, (not RazorPages) you can download a file in code using:

return File(memory, GetContentType(path), Path.GetFileName(path));

But return File is not supported in Razor Pages.

Answer 1

pitaridis is correct, return File exists in Razor Pages, I must have been missing a namespace. This will download a file from Code Behind:

In the page, here's the submit button:

<button type="submit" asp-page-handler="DownloadFile" style="width:75px" 
        class="cancel"> Download </button>

In the PageModel (code behind):

public ActionResult OnPostDownloadFile()
{
    return File("/DownloadableFiles/TestFile34.csv", "application/octet-stream", 
                "NewName34.csv");
}

Note: /DownloadableFiles is in a subfolder of wwwroot

Answer 2

It's also possible to use a GET call instead of POST like this:

Put this in your page code behind:

public ActionResult OnGetDownload()
{
  return File("c:/Directory/FileName.csv", "application/octet-stream", "FileName.csv");
}

And put this on that page:

 <a href="@Url.Page("ThePageName", "Download")>Download</a>

If you want to pass parameters, just include them in the Url.Page call and add parameters to OnGetDownload like this:

public ActionResult OnGetDownload(int Id)
{
  return File("c:/Directory/FileName.csv", "application/octet-stream", "FileName.csv");
}

<a href="@Url.Page("ThePageName", "Download", new { Model.Id })">Download</a>