How to convert byte to file asp.net MVC - asp.net-mvc

Question

I want to download the file that I uploaded in the database. The file stored in the byte array. I have created the getDataStudent function and it is working well.
My controller is below.
public class Student: Controller
{
private StudentViewModel getDataStudent(StudentViewModel model)
{
var students = db.students.ToList();
var documents = documentRepo.GetList_Documents();
var queryJoin1 =
from student in students
from document in documents.Where(w => student .UniqueNumber == w.UniqueNumber).DefaultIfEmpty()
select new StudentDto
{
ID = student.ID,
Name = student.Name,
File = document?.DetailFile ?? null, //file to download
};
IEnumerable <StudentDto> studentss= null;
studentss = queryJoin1;
return studentss;
}
public ActionResult Index(StudentViewModel model)
{
studentViewModel = getDataStudent(model);
return View(studentViewModel );
}
[HttpPost]
public FileResult DownloadFile()
{
//code
}
}
and my view is below
#model Student.Data.ViewModels.StudentViewModel
#using (Html.BeginForm())
{
<table class="table">
<tr>
<th>Name</th>
<th>File</th>
</tr>
#foreach (Student.Data.ViewModels.StudentViewModel item in Model)
{
<tr>
<td>#Html.DisplayFor(modelitem => item.Name)</td>
<td> #Html.DisplayFor(modelitem => item.File)</td>
</tr>
}
</table>
}
File Result is still empty, I confused using FileResult.
can you guys tell me how to download files using FileResult on the controller, using the getDataStudent function that I created.
I have never made a file download function before. please help:)

Answer 1

You can implement like this:
public FileStreamResult DownloadFile()
{
// get your students here
var students = ...
string name = "yourname.txt";
FileInfo info = new FileInfo(name);
if (!info.Exists)
{
using (StreamWriter writer = info.CreateText())
{
foreach(var item in students){
writer.WriteLine("{0} {1}", item.ID, item.Name);
}
}
}
return File(info.OpenRead(), "text/plain");
}