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How can I solve FileSystemException: Cannot retrieve length of file, path ='...' (OS Error: No such file or directory, errno = 2)

I am trying to send a user model from dart to the api where my file is set as "IFormFile" data type in my c# backend.
I tried using the multipart request but all i get is the error stated , i can't understand why it cannot retrieve the length of file.
This is my code:
updateUser() async {
var uri = Uri.parse('http://myIP:8070/api/Users');
var request = http.MultipartRequest('Put', uri);
request.fields['id']="07bb2a17-7cd5-471b-973a-4b77d239b6c3";
request.fields['username']="beeso";
request.fields['email']="jake-username2#gmail.com";
request.fields['password']="Jake123-";
request.fields["oldPassword"]="Jake124-";
request.fields["gender"]="Male";
request.fields["dateOfBirth"]=DateTime.now().toString();
request.fields["name"]="dsjnss";
request.fields["languages"]=["Language1","Language2"].toString();
request.fields["nationalities"]=["Nationality1","Nationality2"].toString();
request.fields["phoneNumber"]="70502030";
request.fields["biography"]="jdnknkdas";
request.fields["info"]="asndasnkdas";
request.fields["religion"]="Christian";
request.fields["location"]="LA";
File imageFile = new File('Anatomy_of_a_Sunset-2.jpg');
var stream = new http.ByteStream(DelegatingStream.typed(imageFile.openRead()));
var length = await imageFile.length();
var multipartFile = new http.MultipartFile('file', stream, length,
filename: basename(imageFile.path));
request.files.add(multipartFile);
Map<String, String> headers = {
"content-type": "application/json"
};
request.headers.addAll(headers);
http.StreamedResponse response = await request.send();
print(response.statusCode);
}
Any help would be appreciated.
This picture shows where my file is located

In Flutter, you can't access files directly from the project. You need to add them to an assets folder (typically assets) and also to pubspec.yaml. Then, instead of using File to read them, you use rootBundle (or one of the Asset classes).
var multipartFile = http.MultipartFile.fromBytes(
'file',
(await rootBundle.load('assets/anatomy.jpg')).buffer.asUint8List(),
filename: 'anatomy.jpg', // use the real name if available, or omit
contentType: MediaType('image', 'jpg'),
);
request.files.add(multipartFile);
While testing your API, you may find it easier to just create a Dart command line project, where you do have access to Files in the project folders.

my case was image uploading problem and I solved it by using
xfile.path that image picker returned
XFile? image = await _picker.pickImage(
source: ImageSource.gallery,
imageQuality: 50,
maxHeight: 500,
maxWidth: 500);
#flutter
#dio

How to open downloaded file on iOS

We're developing mobile application in Xamarin. How can next be accomplished in iOS:
user downloads file from url (http request is made to REST API, secured with Authentication Basic username:secretKey)
file is saved to iOS
user opens a file (allowed are jpg, png, pdf, doc, docx, png)
file is opened in default application (e.g. for images image viewer)
As file operations are platform specific, here's interface definition:
public interface IFileHelper
{
void DownloadFileAndSave(Models.DocumentModel document);
}
Android implementation:
public class FileHelper : IFileHelper
{
// download file and view status in download manager
public void DownloadFileAndSave(Models.DocumentModel document)
{
DownloadManager dm = (DownloadManager)Android.App.Application.Context.GetSystemService(Context.DownloadService);
string url = WebApiUtils.GetBaseUrl() + string.Format("Api/v1/Dms/{0}", document.UniqueId);
DownloadManager.Request request = new Android.App.DownloadManager.Request(Android.Net.Uri.Parse(url)));
request.AddRequestHeader("Authorization", "Basic " + WebApiUtils.GetEncodedCredentials(Auth.Users.Current));
var downloadFile = Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryDownloads);
string path = Path.Combine(downloadFile.AbsolutePath, document.FileName);
request.SetDestinationUri(Android.Net.Uri.FromFile(new Java.IO.File(path)));
request.SetMimeType(document.ContentType);
request.SetNotificationVisibility(DownloadVisibility.VisibleNotifyCompleted);
dm.Enqueue(request);
}
In Android file is simply stored on the filesystem and with File Explorer which is by default installed on any Android (i.e. My Files -> device storage -> Download), the file is opened in default application for file's mime type. Everything fine on Android.
Apple iOS implementation:
public class FileHelper : IFileHelper
{
public void DownloadFileAndSave(Models.DocumentModel document)
{
WebClient webClient = new WebClient();
webClient.Headers.Add(HttpRequestHeader.Authorization, "Basic " + WebApiUtils.GetEncodedCredentials(Auth.Users.Current));
webClient.DownloadDataAsync(new System.Uri(WebApiUtils.GetBaseUrl() + string.Format(Consts.ApiUrls.GetDocument, document.UniqueId)));
webClient.DownloadDataCompleted += (sender, e) =>
{
byte[] content = e.Result;
string path = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), document.FileName);
// doesn't throw exception therefore saved ok
File.WriteAllBytes(path, content);
Uri uri = new Uri(String.Format("file://{0}", path));
// doesn't work.
Device.OpenUri(uri);
};
}
}
Is there any other way to open downloaded file in default application. If I open url e.g. http://example.com/files/file1.png it opens the file in safari, but I can't put Authorization: Basic headers in Device.OpenUri.
I read about Load Non-Web Documents with WebView but you would have to build each file as BundleResource.

As Code Warrior commented there is one approach posted on link: https://forums.xamarin.com/discussion/36964/why-is-it-that-nothing-is-working-to-open-an-existing-local-pdf-file-in-the-ios-portion-of-my-pcl.
But Save image action doesn't work, everything else seems to work.
public void DownloadFileAndSave(Models.DocumentModel document)
{
WebClient webClient = new WebClient();
webClient.Headers.Add(HttpRequestHeader.Authorization, "Basic " + WebApiUtils.GetEncodedCredentials(Auth.Users.Current));
string tempPath = Path.GetTempPath();
string localFilename = Path.GetFileName(document.FileName);
string localPath = Path.Combine(tempPath, localFilename);
webClient.DownloadFileCompleted += (sender, e) =>
{
Device.BeginInvokeOnMainThread(() =>
{
QLPreviewItemFileSystem prevItem = new QLPreviewItemFileSystem(localFilename, localPath); // ql = quick look
QLPreviewController previewController = new QLPreviewController()
{
DataSource = new PreviewControllerDS(prevItem)
};
UIApplication.SharedApplication.KeyWindow.RootViewController.PresentViewController(previewController, true, null);
});
};
// download file
Uri uri = new System.Uri(WebApiUtils.GetBaseUrl() + string.Format(Consts.ApiUrls.GetDocument, document.UniqueId));
webClient.DownloadFileAsync(uri, localPath);
}
When Save image is triggered I get next error:
2017-10-03 13:45:56.797 MyApp.iOS[477:61030] Video
/private/var/mobile/Containers/Data/Application/33D7139A-53E0-4A2E-8C78-D3D13A2259B0/tmp/water-h2o-md.png
cannot be saved to the saved photos album: Error
Domain=AVFoundationErrorDomain Code=-11828 "Cannot Open"
UserInfo={NSUnderlyingError=0x1c0445d60 {Error
Domain=NSOSStatusErrorDomain Code=-12847 "(null)"},
NSLocalizedFailureReason=This media format is not supported.,
NSURL=file:///private/var/mobile/Containers/Data/Application/33D7139A-53E0-4A2E-8C78-D3D13A2259B0/tmp/water-h2o-md.png,
NSLocalizedDescription=Cannot Open}
iOS treates image as video? Is this a bug on iOS or am I something missing.
UPDATE
It turns out that next permissions was missing in Info.plist file:
<key>NSPhotoLibraryUsageDescription</key>
<string>Application needs to access photos</string>
<!-- for iOS 11 -->
<key>NSPhotoLibraryAddUsageDescription</key>
<string>Application needs to access photos</string>
Now Save Image action is working ok. But seriously Apple could return more appropriate error than Video image.jpg cannot be saved ...

Show download progress in browser

I'm working in a function to download pdfs from DropBox, I'm using ASP.net Core , everything works good. The only thing is that when you click in the download link it doesn't show any message and downloads the file. I would like to show the download progress like usually happens when we download something from Internet, I don't want any dialog to appear, just to show that the file was downloaded like normally happens in any browser like Chrome or IE and then have the choices 'Show in Folder' and things like that, what would I need to add?
public async Task DownloadPdf()
{
DropboxClient client2 = new DropboxClient("cU5M-a4exaAAAAAAAAABDVZsKdpPteNmwHslOeFEo-HByuOr4v4ONvXoAMCFyOXH");
string folder = "MyFolder";
string file = "Test PDF.pdf";
using (var response = await client2.Files.DownloadAsync("/" + folder + "/" + file))
{
using (var fileStream = System.IO.File.Create(#"C:\Users\User\Downloads\Test.pdf"))
{
(await response.GetContentAsStreamAsync()).CopyTo(fileStream);
}
}
}

I have a asp.net core project with an API that returns a file:
[HttpGet("{id}")]
public IActionResult Get(int id) {
byte[] fileContent = READ_YOUR_FILE();
FileContentResult result = new FileContentResult(fileContent, "application/octet-stream") {
FileDownloadName = id.ToString()
};
return result;
}
If I access in my browser the URL from this API (myapp/api/mycontroller/id), then I can see the file downloading.

Download File through headers from different server

I have PDF file placed on different (FILE-Server) server machine, and the IIS machine on which my MVC application is hosted have rights to that File-Server. From IIS machine i can access the file through following URI:
file://file-server/data-folder/pdf/19450205.pdf
I want to enable my MVC app's users to download their respective files by clicking on download link or button. So probably i would have to write some Action for that link/button.
I tried to use File return type for my Action method in following way:
public ActionResult FileDownload()
{
string filePth = #"file://file-server/data-folder/pdf/19450205.pdf";
return File(filePth , "application/pdf");
}
but the above code gives exception of URI not supported.
I also tried to use FileStream to read bytes inside array return that bytes towards download, but FileStream also gives error of not proper "Virtual Path" as the file is not placed inside virtual path, its on separate server.

public ActionResult Download()
{
var document = = #"file://file-server/data-folder/pdf/19450205.pdf";
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);
}

Thanks for the replies, but both suggestion did not work.
as file needs to be accessed over URI, using FileInfo gives error: URI formats are not supported.
I managed to get this done through following mechanism:
public ActionResult FaxFileDownload()
{
string filePth = #"file://file-server/data-folder/pdf/19450205.pdf";
WebClient wc = new WebClient();
Stream s = wc.OpenRead(filePth);
return File(s, "application/pdf");
}
Thanks to All.

How can I read uploaded file in CefSharp?

User uses my browser based on CefSharp. He uploads a file (which is selected in file input HTML control) to known server using XMLHttpRequest (it's JavaScript object for AJAX requests). I want to intercept and to read the uploading file in my browser.
I do the same in my browser based on Awesomium using IResourceInterceptor. It's easy, because ResourceRequest parameter contains full local path of the file. How can I do the same in CefSharp browser?
How user uploads file using XMLHttpRequest (JavaScript):
var file = document.getElementById('fileInput').files[0];
var formData = new FormData();
formData.append('file', file);
var xhr = new XMLHttpRequest();
xhr.responseType = 'arraybuffer';
xhr.open('POST', '/upload', true);
xhr.send(formData);
Awesomium way to intercept user's file (C#):
class MyResourceInterceptor : IResourceInterceptor
{
public ResourceResponse OnRequest(ResourceRequest request)
{
// intercept URL with /upload path only
if (request.Url.AbsolutePath != "/upload")
{
return null;
}
// full local path for user's file
var filePath = request[1].FilePath;
// now I can read and process the file
}
public bool OnFilterNavigation(NavigationRequest request)
{
return false;
}
}

CefSharp doesn't currently expose a way to access Post Data which is what I'm guessing you require.
I have implemented a PR that contains a basic implementation, feel free to test it out. See https://github.com/cefsharp/CefSharp/pull/1113
The other option you have is implement OnFileDialog, you'd have to display your own dialog, simple enough though.
https://github.com/cefsharp/CefSharp/blob/cefsharp/41/CefSharp/IDialogHandler.cs#L38