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Returning file from ASP.NET Controller [duplicate]

I'm encountering a problem sending files stored in a database back to the user in ASP.NET MVC. What I want is a view listing two links, one to view the file and let the mimetype sent to the browser determine how it should be handled, and the other to force a download.
If I choose to view a file called SomeRandomFile.bak and the browser doesn't have an associated program to open files of this type, then I have no problem with it defaulting to the download behavior. However, if I choose to view a file called SomeRandomFile.pdf or SomeRandomFile.jpg I want the file to simply open. But I also want to keep a download link off to the side so that I can force a download prompt regardless of the file type. Does this make sense?
I have tried FileStreamResult and it works for most files, its constructor doesn't accept a filename by default, so unknown files are assigned a file name based on the URL (which does not know the extension to give based on content type). If I force the file name by specifying it, I lose the ability for the browser to open the file directly and I get a download prompt. Has anyone else encountered this?
These are the examples of what I've tried so far.
//Gives me a download prompt.
return File(document.Data, document.ContentType, document.Name);
//Opens if it is a known extension type, downloads otherwise (download has bogus name and missing extension)
return new FileStreamResult(new MemoryStream(document.Data), document.ContentType);
//Gives me a download prompt (lose the ability to open by default if known type)
return new FileStreamResult(new MemoryStream(document.Data), document.ContentType) {FileDownloadName = document.Name};
Any suggestions?
UPDATE:
This questions seems to strike a chord with a lot of people, so I thought I'd post an update. The warning on the accepted answer below that was added by Oskar regarding international characters is completely valid, and I've hit it a few times due to using the ContentDisposition class. I've since updated my implementation to fix this. While the code below is from my most recent incarnation of this problem in an ASP.NET Core (Full Framework) app, it should work with minimal changes in an older MVC application as well since I'm using the System.Net.Http.Headers.ContentDispositionHeaderValue class.
using System.Net.Http.Headers;
public IActionResult Download()
{
Document document = ... //Obtain document from database context
//"attachment" means always prompt the user to download
//"inline" means let the browser try and handle it
var cd = new ContentDispositionHeaderValue("attachment")
{
FileNameStar = document.FileName
};
Response.Headers.Add(HeaderNames.ContentDisposition, cd.ToString());
return File(document.Data, document.ContentType);
}
// an entity class for the document in my database
public class Document
{
public string FileName { get; set; }
public string ContentType { get; set; }
public byte[] Data { get; set; }
//Other properties left out for brevity
}

public ActionResult Download()
{
var document = ...
var cd = new System.Net.Mime.ContentDisposition
{
// for example foo.bak
FileName = document.FileName,
// always prompt the user for downloading, set to true if you want
// the browser to try to show the file inline
Inline = false,
};
Response.AppendHeader("Content-Disposition", cd.ToString());
return File(document.Data, document.ContentType);
}
NOTE: This example code above fails to properly account for international characters in the filename. See RFC6266 for the relevant standardization. I believe recent versions of ASP.Net MVC's File() method and the ContentDispositionHeaderValue class properly accounts for this. - Oskar 2016-02-25

I had trouble with the accepted answer due to no type hinting on the "document" variable: var document = ... So I'm posting what worked for me as an alternative in case anybody else is having trouble.
public ActionResult DownloadFile()
{
string filename = "File.pdf";
string filepath = AppDomain.CurrentDomain.BaseDirectory + "/Path/To/File/" + filename;
byte[] filedata = System.IO.File.ReadAllBytes(filepath);
string contentType = MimeMapping.GetMimeMapping(filepath);
var cd = new System.Net.Mime.ContentDisposition
{
FileName = filename,
Inline = true,
};
Response.AppendHeader("Content-Disposition", cd.ToString());
return File(filedata, contentType);
}

To view file (txt for example):
return File("~/TextFileInRootDir.txt", MediaTypeNames.Text.Plain);
To download file (txt for example):
return File("~/TextFileInRootDir.txt", MediaTypeNames.Text.Plain, "TextFile.txt");
note: to download file we should pass fileDownloadName argument

Darin Dimitrov's answer is correct. Just an addition:
Response.AppendHeader("Content-Disposition", cd.ToString()); may cause the browser to fail rendering the file if your response already contains a "Content-Disposition" header. In that case, you may want to use:
Response.Headers.Add("Content-Disposition", cd.ToString());

I believe this answer is cleaner, (based on
https://stackoverflow.com/a/3007668/550975)
public ActionResult GetAttachment(long id)
{
FileAttachment attachment;
using (var db = new TheContext())
{
attachment = db.FileAttachments.FirstOrDefault(x => x.Id == id);
}
return File(attachment.FileData, "application/force-download", Path.GetFileName(attachment.FileName));
}

Below code worked for me for getting a pdf file from an API service and response it out to the browser - hope it helps;
public async Task<FileResult> PrintPdfStatements(string fileName)
{
var fileContent = await GetFileStreamAsync(fileName);
var fileContentBytes = ((MemoryStream)fileContent).ToArray();
return File(fileContentBytes, System.Net.Mime.MediaTypeNames.Application.Pdf);
}

FileVirtualPath --> Research\Global Office Review.pdf
public virtual ActionResult GetFile()
{
return File(FileVirtualPath, "application/force-download", Path.GetFileName(FileVirtualPath));
}

Action method needs to return FileResult with either a stream, byte[], or virtual path of the file. You will also need to know the content-type of the file being downloaded. Here is a sample (quick/dirty) utility method. Sample video link
How to download files using asp.net core
[Route("api/[controller]")]
public class DownloadController : Controller
{
[HttpGet]
public async Task<IActionResult> Download()
{
var path = #"C:\Vetrivel\winforms.png";
var memory = new MemoryStream();
using (var stream = new FileStream(path, FileMode.Open))
{
await stream.CopyToAsync(memory);
}
memory.Position = 0;
var ext = Path.GetExtension(path).ToLowerInvariant();
return File(memory, GetMimeTypes()[ext], Path.GetFileName(path));
}
private Dictionary<string, string> GetMimeTypes()
{
return new Dictionary<string, string>
{
{".txt", "text/plain"},
{".pdf", "application/pdf"},
{".doc", "application/vnd.ms-word"},
{".docx", "application/vnd.ms-word"},
{".png", "image/png"},
{".jpg", "image/jpeg"},
...
};
}
}

If, like me, you've come to this topic via Razor components as you're learning Blazor, then you'll find you need to think a little more outside of the box to solve this problem. It's a bit of a minefield if (also like me) Blazor is your first forray into the MVC-type world, as the documentation isn't as helpful for such 'menial' tasks.
So, at the time of writing, you cannot achieve this using vanilla Blazor/Razor without embedding an MVC controller to handle the file download part an example of which is as below:
using Microsoft.AspNetCore.Mvc;
using Microsoft.Net.Http.Headers;
[Route("api/[controller]")]
[ApiController]
public class FileHandlingController : ControllerBase
{
[HttpGet]
public FileContentResult Download(int attachmentId)
{
TaskAttachment taskFile = null;
if (attachmentId > 0)
{
// taskFile = <your code to get the file>
// which assumes it's an object with relevant properties as required below
if (taskFile != null)
{
var cd = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
{
FileNameStar = taskFile.Filename
};
Response.Headers.Add(HeaderNames.ContentDisposition, cd.ToString());
}
}
return new FileContentResult(taskFile?.FileData, taskFile?.FileContentType);
}
}
Next, make sure your application startup (Startup.cs) is configured to correctly use MVC and has the following line present (add it if not):
services.AddMvc();
.. and then finally modify your component to link to the controller, for example (iterative based example using a custom class):
<tbody>
#foreach (var attachment in yourAttachments)
{
<tr>
<td>#attachment.Filename </td>
<td>#attachment.CreatedUser</td>
<td>#attachment.Created?.ToString("dd MMM yyyy")</td>
<td><ul><li class="oi oi-circle-x delete-attachment"></li></ul></td>
</tr>
}
</tbody>
Hopefully this helps anyone who struggled (like me!) to get an appropriate answer to this seemingly simple question in the realms of Blazor…!

Want to pass data from the controller to the view WITHOUT adding it to the URL

I'm using ASP.Net MVC 5, and I want to pass data from the controller to the view WITHOUT adding it to the URL.
I've tried it like this:
public ActionResult Index(LoginViewModel loginViewModel)
{
var landingPgVm = new LandingPgViewModel();
landingPgVm.ElectionName = loginViewModel.ElectionName;
landingPgVm.LandingPageTitle = loginViewModel.LandingPageTitle;
landingPgVm.LandingPageMessage = loginViewModel.LandingPageMessage;
return View("Landing", landingPgVm);
}
And this:
public ActionResult Index(LoginViewModel loginViewModel)
{
var landingPgVm = new LandingPgViewModel();
landingPgVm.ElectionName = loginViewModel.ElectionName;
landingPgVm.LandingPageTitle = loginViewModel.LandingPageTitle;
landingPgVm.LandingPageMessage = loginViewModel.LandingPageMessage;
ViewData["lpvm"] = landingPgVm;
return View("Landing");
}
And still, I get this:
http://localhost:nnnnn/Landing?VotingIsOpen=False&UserIp=%3A%3A1&BrowserAgent=Mozilla%2F5.0%20%28Windows%20NT%2010.0%3B%20Win64%3B%20x64%29%20AppleWebKit%2F537.36%20%28KHTML%2C%20like%20Gecko%29%20Chrome%2F73.0.3683.103%20Safari%2F537.36&ElectionId=1&LoginId=********&LoginPin=*********&ElectionName=2019%20Member-at-Large%20Board%20Election&LandingPageTitle=Success%21&LandingPageMessage=Landing%20Page%20MESSAGE

So sorry that I let my frustration at, what turned out to be MYSELF, spill over onto these pages.
It's been some time since I've done a 'standard' MVC site and forgot how the logic is supposed to flow. (Sometimes it takes getting all the way to posting to SO before I finally figure out/realize the error(s) of my way(s)).
Thanks to info found on the MS docs site here (https://learn.microsoft.com/en-us/aspnet/mvc/overview/security/create-an-aspnet-mvc-5-web-app-with-email-confirmation-and-password-reset), namely, the POST method example under the "You must also update the HttpPost Login action method:" text, I've got it figured out.

How do I determine which View is used when calling View(Object model)

First, some context:
Language - C#
Platform - .Net Framework 4.5
Project type - ASP.Net MVC 4
I am trying to determine which View in an MVC project is handling an explicit call to the following method. The MSDN docs for the method are here: http://msdn.microsoft.com/EN-US/library/dd492930.aspx
protected internal ViewResult View(
Object model
)
The original Author is using a View to generate a PDF file with a third-party library. I need to modify the view to include additional information.
The problem: I'm having trouble finding which View to modify. There are hundreds of them, and (IMHO) they are poorly named and organized. The basic process for generating a PDF looks like this. I'm getting confused in between steps 3 and 4.
An Entity's ID is passed to an ActionResult
The Entity is retrieved from the backing store
The model is passed to the Controller.View method mentioned above:
var viewModel = View(model);
var xmlText = RenderActionResultToString(viewModel);
The resulting ViewResult is used with an instance of ControllerContext to generate HTML as if being requested by a browser.
The resulting HTML is passed to the third-party tool and converted to a PDF.
I understand everything else very clearly. What I don't understand is how the call to View(model) determines which View file to use when returning the ViewResult. Any help greatly appreciated!
I'm including the code below, in case it helps anybody determine the answer.
The ActionResult:
public ActionResult ProposalPDF(String id, String location, bool hidePrices = false)
{
var proposal = _adc.Proposal.GetByKey(int.Parse(id));
var opportunity = _adc.Opportunity.GetByKey(proposal.FkOpportunityId.Value);
ViewData["AccountId"] = opportunity.FkAccountId;
ViewData["AccountType"] = opportunity.FkAccount.FkAccountTypeId;
ViewData["Location"] = location;
ViewData["HidePrices"] = hidePrices;
return ViewPdf(proposal);
}
The ViewPDF method:
protected ActionResult ViewPdf(object model)
{
// Create the iTextSharp document.
var document = new Document(PageSize.LETTER);
// Set the document to write to memory.
var memoryStream = new MemoryStream();
var pdfWriter = PdfWriter.GetInstance(document, memoryStream);
pdfWriter.CloseStream = false;
document.Open();
// Render the view xml to a string, then parse that string into an XML dom.
var viewModel = View(model);
var xmlText = RenderActionResultToString(viewModel);
var htmlPipelineContext = new HtmlPipelineContext();
htmlPipelineContext.SetTagFactory(Tags.GetHtmlTagProcessorFactory());
//CSS stuff
var cssResolver = XMLWorkerHelper.GetInstance().GetDefaultCssResolver(false);
var cssResolverPipeline = new CssResolverPipeline(cssResolver, new HtmlPipeline(htmlPipelineContext, new PdfWriterPipeline(document, pdfWriter)));
var xmlWorker = new XMLWorker(cssResolverPipeline, true);
var xmlParser = new XMLParser(xmlWorker);
xmlParser.Parse(new StringReader(xmlText));
// Close and get the resulted binary data.
document.Close();
var buffer = new byte[memoryStream.Position];
memoryStream.Position = 0;
memoryStream.Read(buffer, 0, buffer.Length);
// Send the binary data to the browser.
return new BinaryContentResult(buffer, "application/pdf");
}
The RenderActionResultToString helper method:
protected string RenderActionResultToString(ActionResult result)
{
// Create memory writer.
var sb = new StringBuilder();
var memWriter = new StringWriter(sb);
// Create fake http context to render the view.
var fakeResponse = new HttpResponse(memWriter);
var fakeContext = new HttpContext(System.Web.HttpContext.Current.Request, fakeResponse);
var fakeControllerContext = new ControllerContext(new HttpContextWrapper(fakeContext), this.ControllerContext.RouteData, this.ControllerContext.Controller);
var oldContext = System.Web.HttpContext.Current;
System.Web.HttpContext.Current = fakeContext;
// Render the view.
result.ExecuteResult(fakeControllerContext);
// Restore data.
System.Web.HttpContext.Current = oldContext;
// Flush memory and return output.
memWriter.Flush();
return sb.ToString();
}

I'm not exactly sure what you're asking, but, when you call View(model) the view that is chosen is based upon conventions.
Here is an example:
public class HerbController : Controller {
public ActionResult Cilantro(SomeType model) {
return View(model)
}
}
That will look for a view file called Cilantro.cshtml in a folder called Herb (Views/Herb/Cilantro.cshtml). The framework will also look in the Shared directory as well in case it is a view that is meant to be shared across multiple results.
However, you may also want to look at the Global.asax file to see if there are any custom view paths being setup for the view engine. The example I gave above is based upon the default conventions of ASP.NET MVC. You can override them to meet your needs better if needed.

The convention for views is that they are in a folder named after the controller (without "Controller") and the .cshtml file inside that folder is named after the calling action. In your case, that should be:
~/Views/[Controller]/ProposalPdf.cshtml

The logic to determine which view template will be used is in the ViewResult that is returned from the call
var viewModel = View(model);
And how the view is selected is determined by the configured ViewEngine(s), but it will use the current Area, Controller and Action route values to determine what view should be served.
What the route values are for the ProposalPDF action will depend on how your routing is configured, but assuming the defaults, the action route value will be ProposalPDF, the controller route value will be the name of the controller class in which this action resides (minus the Controller suffix) and the area will be the area folder in which the controller lives, with a value of empty string if in the default controller folder. Then using these route values, a view will be looked up in the Views folder using the following convention
~/Views/{Area}/{Controller}/{View}.cshtml
There is always Glimpse that can help with providing runtime Diagnostics too, such as which View file was used to serve up the returned page, although I'm not sure how this would look when a ViewResult is executed internally to provide the contents of a file.

How to return multiple images from controller method?

I have an ASP.NET MVC controller that generates images (they are stored in memory, I don't want to store them on the hard drive) and should return them to my view.
The problem is: I don't how know how to return multiple images from one controller method (I want to show the images in 1 view). I know that I can return a single image with the FileResult for example, but I can't find out (not on google/stackoverflow) how to return multiple images from the same method. Splitting the method up in multiple methods can't be done. Oh, all of the images are converted to a byte[], but that can be reversed if necessary.

This should work. Note I am reading my images from disk for my example but they can come from memory or anywhere. Then on the client side use java-script to display them.
[HttpGet]
public JsonResult Images()
{
var image1Base64 = Convert.ToBase64String(System.IO.File.ReadAllBytes(Server.MapPath("~/Images/1.jpg")));
var image2Base64 = Convert.ToBase64String(System.IO.File.ReadAllBytes(Server.MapPath("~/Images/2.jpg")));
var jsonResult = Json(new { image1 = image1Base64, image2 = image2Base64 }, JsonRequestBehavior.AllowGet);
jsonResult.MaxJsonLength = int.MaxValue;
return jsonResult;
}

If you have access to the MIME type of the image, you could always render them as Base64-encoded images, instead of making another request to a different controller method. This is a view model I use:
public class ImageViewModel
{
public string FileName { get; set; }
public string MIME { get; set; }
public byte[] Data { get; set; }
public override string ToString()
{
return string.Format(#"data:{0};base64,{1}", MIME.ToLower(), Convert.ToBase64String(Data));
}
}
You can use the Filename property in the alt attribute of the <img /> tag, so the markup & model-binding in your view would look something like this (assuming Razor syntax):
<img src="#model.ToString()" alt="#model.FileName" />
You do lose image-caching, AFAIK - that hasn't been an issue for me, but is understandably a deal-breaker for some.

I think that you can solve it in another way, instead of returning multiple images, you can create a utility method that loads the image in the controller
public FileContentResult GetImage(int imageId)
{
var image = GetImageById(imageId); // get from a list for example
return File(image, "image/jpeg"); // your image Mime type
}
and in the View you can do the following, iterate over the images
#foreach (var image in Model)
{
<img alt="" src="#Url.Action("GetImage", "ControllerName", new {imageId =image.Id})"/>
}

You wish to show multiple images based on input of the user, but don't want to save to the hard disk (chat). Therefor I recommand you using a session variable to save the users input in. And the use a simple FileResult to return multiple images based on that session variable.
http://blog.theobjectguy.com/2009/12/session-with-style.html

If your requirement is to show multiple images in one view it would be easier to use 2 action methods. One that returns a image with FileResult and another where you just use standard html img tags pointing the first action method

I want to display a PDF on a new page/window?

I have a print method that shows a PDF i want it showing in a new window!
This is what i want displaying on a new page, tab, window!!!
return File(arrStream, "application/pdf");
My Print method:
public ActionResult Print(int id) // sales contract Id
{
ParameterFields paramFields = CreateParameterFields(id); // pass the id of the contract
// Save the report run details
Guid reportRunId;
SaveReportRunDetails(paramFields, out reportRunId);
try
{
<<< Print code >>>
//Open a new page on this return
return File(arrStream, "application/pdf");
}
catch (Exception err)
{
ViewBag.ErrorMessage = err.Message;
return RedirectToAction("Edit", new { id = id, error = err.Message });
}
}
This is a controller, and i can't mix client-side scripting with sever side code, if i had it in a link that points to this controller then even my errors would display on a new page, this would be bad and annoying for users.
How can i go about achieving my goal?

To open the pdf in a new page simply use target="_blank" in the calling your method.
Looking at your code it don't seem that you are using a post, so a simple
text
should solve your problem