ASP.NET Core Response headers on a FileStreamResult

Question

I am doing a .mp4 file download from Azure Blob storage and pushing that to the UI. The download works fine, the issue is it doesn't look like the headers are set correctly for content-length. Thus you cannot track the download time because the browser only says what has been downloaded and not how much is left and the estimated time. Is my code for the response wrong or should I change my request? My code as follows:

[HttpGet("VideoFileDownload")]
public IActionResult VideoFileDownloadAsync([FromQuery]int VideoId)
{
     ...code to get blob file
     return new FileStreamResult(blob.OpenRead(), new MediaTypeHeaderValue("application/octet-stream")
}

I have played around with various request and response headers but it makes no difference.

The files are big and I know the old asp.net way of checking for range headers and then do a chunked stream but I want to use the new features in .net core which doesn't work as expected or maybe I just don't understand it thoroughly. Can somebody give me a working sample of a file download with asp.net core code.

Answer 1

If you have the file size, you can set the response's content length in the Response object just before returning the FileStreamResult, like this:

[HttpGet("VideoFileDownload")]
public IActionResult VideoFileDownloadAsync([FromQuery]int VideoId)
{
     ...code to get blob file
     long myFileSize = blob.Length; // Or wherever it is you can get your file size from.
     this.Response.ContentLength = myFileSize;
     return new FileStreamResult(blob.OpenRead(), new MediaTypeHeaderValue("application/octet-stream")
}