In the file picker Windows 8 sample a file is saved like this:
CachedFileManager.DeferUpdates(file);
await FileIO.WriteTextAsync(file, stringContent);
FileUpdateStatus status = await CachedFileManager.CompleteUpdatesAsync(file);
I'm serialising an object as XML so doing it slightly differently:
// CachedFileManager.DeferUpdates(file);
var ras = await file.OpenAsync(FileAccessMode.ReadWrite);
var outStream = ras.GetOutputStreamAt(0);
var serializer = new XMLSerializer();
serializer.Write(myObject, outStream);
// FileUpdateStatus status = await CachedFileManager.CompleteUpdatesAsync(file);
It works with or without the CachedFileManager (commented out above).
So, should I include the CachedFileManager and if I do use it am I saving the file in the right way.
This code works and saves the file fine, but I don't like including code that I don't understand.
Yes, this code will work without CachedFileManager. But, when you use CachedFileManager, you inform the file provider that the file is in process of change. If your file is located on SkyDrive it is faster to create a file and upload it at once instead of update it multiple times.
You can have the full story there : http://www.jonathanantoine.com/2013/03/25/win8-the-cached-file-updater-contract-or-how-to-make-more-useful-the-file-save-picker-contract/
It simply tells the "repository" app to upload the file.
Related
I tried to open a locally stored pdf with xamarin.
example code:
var files = Directory.GetFiles(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData));
var filepath = "file://" + files[0];
if (File.Exists(filepath))
{
await Launcher.OpenAsync(filepath);
}
But the file does not open. The only message I get is (android device):
what do I miss?
EDIT
the variable filepath contains:
file:///data/user/0/com.companyname.scgapp_pdfhandler/files/.config/test.pdf
also tried
file://data/user/0/com.companyname.scgapp_pdfhandler/files/.config/test.pdf
does not help
Figured I would add my comment as an answer for easier visibility in case others run into it in the future.
Pass a OpenFileRequest object instead, if you use a string it has to be the correct uri scheme for it. I suspect the uri scheme you are passing to it isn't something that is understood by the system
I am trying to create PDF file using PDFTron in application which runs in the UWP environment. I am able to create a file successfully. Depending on user input that newly created file might need to be renamed or completely deleted from the system. Although when I try to access the file that was just created the system throws the following exception:
Exception thrown: 'System.IO.IOException' in System.IO.FileSystem.dll The process cannot access the file (filename) because it is being used by another process.
The following part show what is used for the file to be created:
await sdfDoc.SaveAsync(filePath, SDFDocSaveOptions.e_linearized, "%PDF-1.5");
sdfDoc.Dispose();
And this is my delete implementation:
var filedelete = Task.Run(() => File.Delete(filePath));
The creation of the file is running on a seperate Task and the deletion takes place upon a button press.
I understand the nature of the exception, although I was wondering if the resources of the file are returned to the system from PDFTron after the creation of the file?
Any help or direction would be much appreciated.
Thank you.
PDFNet uses reference counting internally to know when to release the filesystem handles and memory.
For example, the following would trigger the issue where the file is still locked.
PDFDoc doc = new PDFDoc(input_filename);
doc.InitSecurityHandler();
SDFDoc sdfdoc = doc.GetSDFDoc();
await sdfdoc.SaveAsync(output_file_path, SDFDocSaveOptions.e_linearized, "%PDF-1.5");
sdfdoc.Dispose();
await Task.Run(() => File.Delete(output_file_path)); // fails, as PDFDoc still has reference.
But this would work as expected.
using(PDFDoc doc = new PDFDoc(input_filename))
{
doc.InitSecurityHandler();
SDFDoc sdfdoc = doc.GetSDFDoc();
await sdfdoc.SaveAsync(output_file_path, SDFDocSaveOptions.e_linearized, "%PDF-1.5");
sdfdoc.Dispose();
}
await Task.Run(() => File.Delete(output_file_path)); // works
Note the using statement for the PDFDoc instance, and the manual dispose of the SDFDoc instance, though you could use a using statement on that also.
I know that there are tons of examples of multi-part form data uploading in ASP.net. However, all of them just upload files to the server, and use System.IO to write it to server disk space. Also, the client side implementations seem to handle files only in uploading, so I can't really use existing upload plugins.
What if I have an existing record and I want to upload images and associate them with the record? Would I need to write database access code in the upload (Api) function, and if so, how do I pass that record's PK with the upload request? Do I instead upload the files in that one request, obtain the file names generated by the server, and then make separate API calls to associate the files with the record?
While at it, does anyone know how YouTube uploading works? From a user's perspective, it seems like we can upload a video, and while uploading, we can set title, description, tags, etc, and even save the record. Is a record for the video immediately created before the API request to upload, which is why we can save info even before upload completes?
Again, I'm not asking HOW to upload files. I'm asking how to associate uploaded files with an existing record and the API calls involved in it. Also, I am asking for what API calls to make WHEN in the user experience when they also input information about what they're uploading.
I'm assuming you're using an api call to get the initial data for displaying a list of files or an individual file. You would have to do this in order to pass the id back to the PUT method to update the file.
Here's a sample of the GET method:
[HttpGet]
public IEnumerable<FileMetaData> Get()
{
var allFiles = MyEntities.Files.Select(f => new FileMetaData()
{
Name = f.Name,
FileName = f.FileName,
Description = f.Description,
FileId = f.Id,
ContentType = f.ContentType,
Tags = f.Tags,
NumberOfKB = f.NumberOfKB
});
return allFiles;
}
Here's a sample of the POST method, which you can adapt to be a PUT (update) instead:
[HttpPost]
[ValidateMimeMultipartContentFilter]
public async Task<IHttpActionResult> PutFile()
{
try
{
var streamProvider =
await Request.Content.ReadAsMultipartAsync(new InMemoryMultipartFormDataStreamProvider());
//We only allow one file
var thisFile = files[0];
//For a PUT version, you would grab the file from the database based on the id included in the form data, instead of creating a new file
var file = new File()
{
FileName = thisFile.FileName,
ContentType = thisFile.ContentType,
NumberOfKB = thisFile.ContentLength
};
//This is the file metadata that your client would pass in as formData on the PUT / POST.
var formData = streamProvider.FormData;
if (formData != null && formData.Count > 0)
{
file.Id = formData["id"];
file.Description = formData["description"];
file.Name = formData["name"] ?? string.Empty;
file.Tags = formData["tags"];
}
file.Resource = thisFile.Data;
//For your PUT, change this to an update.
MyEntities.Entry(file).State = EntityState.Detached;
MyEntities.Files.Add(file);
await MyEntities.SaveChangesAsync();
//return the ID
return Ok(file.Id.ToString());
}
I got the InMemoryMultipartFormDataStreamProvider from this article:
https://conficient.wordpress.com/2013/07/22/async-file-uploads-with-mvc-webapi-and-bootstrap/
And adapted it to fit my needs for the form data I was returning.
Quick search here yielded nothing. So, I have started using some rather roundabout ways to use StreamWriter in my WinRT Application. Reading works well, writing works differently. What' I'm seeing is that when I select my file to write, if I choose a new file then no problem. The file is created as I expect. If I choose to overwrite a file, then the file is overwritten to a point, but the point where the stream stops writing, if the original file was large, then the old contents exist past where my new stream writes.
The code is as such:
public async void WriteFile(StorageFile selectedFileToSave)
{
// At this point, selectedFileToSave is from the Save File picker so can be a enw or existing file
StreamWriter writeStream;
Encoding enc = new UTF8Encoding();
Stream dotNetStream;
dotNetStream = await selectedFileToSave.OpenStreamForWriteAsync();
StreamWriter writeStream = new StreamWriter(dotNetStream, enc);
// Do writing here
// Close
writeStream.Write(Environment.NewLine);
await writeStream.FlushAsync();
await dotNetStream.FlushAsync();
}
Can anyone offer clues on what I could be missing? There are lots of functions missing in WinRT, so not really following ways to get around this
Alternatively you can set length of the stream to 0 with SetLength method before using StreamWriter:
var stream = await file.OpenStreamForWriteAsync();
stream.SetLength(0);
using (var writer = new StreamWriter(stream))
{
writer.Write(text);
}
Why not just use the helper methods in FileIO class? You could call:
FileIO.WriteTextAsync(selectedFileToSave, newTextContents);
If you really need a StreamWriter, first truncate the file by calling
FileIO.WriteBytesAsync(selectedFileToSave, new byte[0]);
And then continue with your existing code.
Where can i find folder with installed modern ui apps? Im developing some app which uses .txt files to store information (win8 doesnot support datebase on arm - facepalm) but they seem to not work properly - thats why i want to access them.
Thanks!
That is not the correct way of doing things in Metro. I assume you mean db files, or txt files. Simply access the local text file from the project folder.
Here is a great tutorial on how you would go about doing so: http://www.codeproject.com/Articles/432876/Windows-8-The-Right-Way-to-Read-Write-Files-in-Win
An example:
private async void ProjectFile()
{
// settings
var _Path = #"Metro.Helpers.Tests\MyFolder\MyFolder.txt";
var _Folder = Windows.ApplicationModel.Package.Current.InstalledLocation;
// acquire file
var _File = await _Folder.GetFileAsync(_Path);
Assert.IsNotNull(_File, "Acquire file");
// read content
var _ReadThis = await Windows.Storage.FileIO.ReadTextAsync(_File);
Assert.AreEqual("Hello world!", _ReadThis, "Contents correct");
}