In Asp.Net Core, how can I get the multipart/form-data from the body? - asp.net-core

Question

In Asp.Net Core, it appears that they have done away with the Request.Content.ReadAsMultipartAsync functionality in favor of the IFormFile.
This makes uploading where you have an actual file a LOT easier, however, I have a use case where I need to upload a file to browser memory, process it, then send it as part of the multi-form data in the body. IFormFile cannot see this as there is no actual file to read. It only works if you have a filename property on the Content-Disposition and an actual file on the client to upload.
In my Asp.Net 4 app, I could read the mutlipart data in the body whether that was sent between boundaries or as an attached file.
How do I accomplish this in .Net Core?

Answer 1

What I figured out is that the multipart values are passed into the HttpRequest.Form as an array of key/value pairs. The "name" value on the body's multipart determines the name of the key.
I created a helper method that grabs both files and form values.
public static List<FileModel> GetFileModelsFromRequest(HttpRequest request)
{
var fileModels = new FileModels();
foreach (var formField in request.Form)
{
// Form data
var fileModelText = formField.Value;
... process and add to the FileModel list
}
if (request.Form.Files != null && request.Form.Files.Count > 0)
{
foreach (var file in request.Form.Files)
{
using (MemoryStream ms = new MemoryStream())
{
// File data
formFile.CopyTo(ms);
}
... process and add to the FileModel list
}
}
return fileModels;
}

Answer 2

I have done it this way. when I had to capture image from webcam and process (show that image in browser) it in browser memory and later on post that image using a form.
public IActionResult Index()
{
var files = HttpContext.Request.Form.Files;
if (files != null)
{
foreach (var file in files)
{
var fileName = file.Name;
}
}
return View();
}
I used a JS library Webcam.js to capture image from webcam and show that image on the same page. and once a user is satisfied with the image, s/he can upload the image to the server.
<!-- Configure settings and attach camera -->
<script language="JavaScript">
Webcam.set({
width: 320,
height: 240,
image_format: 'jpeg',
jpeg_quality: 90
});
Webcam.attach('#camera');
</script>
<!-- handle snapshot and displaying it locally -->
<script language="JavaScript">
function take_snapshot() {
// take snapshot and get image data
Webcam.snap(function (data_uri) {
// display results in page
document.getElementById('imageResults').innerHTML =
'<img src="' +
data_uri +
'"/>';
Webcam.upload(data_uri,
'/Default/Index',
function (code, text) {
console.log('Photo Captured');
});
});
}
</script>
<div class="panel panel-default">
<div class="panel-heading">Camera</div>
<div class="panel-body">
<div id="camera"></div>
<!-- A button for taking snaps -->
<form>
<input type="button" class="btn btn-success" value="Take Snapshot" onClick="take_snapshot()">
</form>
<div class="panel panel-default">
<div class="panel-heading">Captured Image</div>
<div class="panel-body">
<div id="imageResults">captured image will appear here...</div>
</div>
<br />
<br />
</div>
let me know if this is what you are looking for.