Develop Reference

How do I save a Text file on the Universal Windows Platform?

I'm trying to save my text file in UWP, but It always saving to different file. By the way I'm using MVVM architecture.
My Code
FileSavePicker savePicker = new FileSavePicker();
savePicker.SuggestedFileName = "New Text Document";
savePicker.SuggestedStartLocation = PickerLocationId.Desktop;
savePicker.FileTypeChoices.Add("Text Document", new List<string>() { ".txt" });
savePicker.DefaultFileExtension = ".txt";
StorageFile storageFile = await savePicker.PickSaveFileAsync();
if(storageFile != null)
{
CachedFileManager.DeferUpdates(storageFile);
await FileIO.WriteTextAsync(storageFile, Document.Text);
FileUpdateStatus updateStatus = await CachedFileManager.CompleteUpdatesAsync(storageFile);
Document.FileName = savePicker.SuggestedFileName;
Document.IsSaved = true;
}
My code is always saving texts on different file. I'm trying to save my text to same file.

In UWP there is a feature called FutureAccessList. It can be used to save the token of the file, opened with the FilePicker. When you now want to save it again you can retrive the StorageFile by the token and write to it.
Add a FileToken property to your Document class:
public string FileToken { get; set; }
Now when you pick your file you add the file to the FutureAccessList:
...
StorageFile storageFile = await savePicker.PickSaveFileAsync();
if (storageFile != null)
{
CachedFileManager.DeferUpdates(storageFile);
await FileIO.WriteTextAsync(storageFile, Document.Text);
FileUpdateStatus updateStatus = await CachedFileManager.CompleteUpdatesAsync(storageFile);
Document.FileName = savePicker.SuggestedFileName;
Document.IsSaved = true;
//Add the file to the FutureAccessList to get it back later
Document.FileToken = StorageApplicationPermissions.FutureAccessList.Add(storageFile);
}
To retrive the file and save it again:
public async void SaveFile()
{
//Get the file back from the FutureAccessList by its token and write to it
StorageFile file = await StorageApplicationPermissions.FutureAccessList.GetFileAsync(Document.FileToken);
await FileIO.WriteTextAsync(file, Document.Text);
}
Now when you e.g. save your Document class to Json and retrive it after the app restarts you can still use the FileToken to write to the file. There is no need to let the user pick it again using the SaveFilePicker.
When the code above is to complicated or there is no need for this (I don't know what you need this for), you can put a StorageFile propertie directly to your Document class and put the file, that the SaveFilePicker returned in it. But this won't work when restarting the app. The user would always have to pick the file again.

UWP image picker not working for image source

I'm trying to get image picker to work, and it does, but for some reason it won't populate as an image.
var openPicker = new FileOpenPicker
{
ViewMode = PickerViewMode.Thumbnail,
SuggestedStartLocation = PickerLocationId.PicturesLibrary
};
openPicker.FileTypeFilter.Add(".jpg");
openPicker.FileTypeFilter.Add(".jpg");
openPicker.FileTypeFilter.Add(".jpeg");
openPicker.FileTypeFilter.Add(".png");
var file = await openPicker.PickSingleFileAsync();
if (file != null)
{
//Image img = new Image();
userImage.Source = new BitmapImage(new Uri(file.Path));
//await ProcessFile(file);
}
and the image is just simply:
<image name="userImage" height="500px" width="500px"/>

This isn't work because the UWP applications have permissions only for some users folders and even you need to browse their files, you need to specify it in the package.manifest of your application which folders you want to access. For simplification, you could create a copy of the file inside the application data folder and get the path from there or set the image source from the stream of the file, but be careful, the second option maybe lead some high memory usage and leaks. You can find how to avoid this here.

You can set stream as source instead of path.
var result = new BitmapImage();
using (var randomAccessStream = await file.OpenAsync(FileAccessMode.Read))
{
await result.SetSourceAsync(randomAccessStream);
}

How to access StorageFile from another method

So im making a windows store app that you select a file with one button, via file picker, then with another button it processes that file but im having trouble getting the selected file to processing method.
Since the Picker sets one of my text blocks to the path of the file to be displayed for the user i've tried using:
StorageFile file = await StorageFile.GetFileFromPathAsync(fullFilePath.Text);
But due to Windows RT limitations I just get access it denied from most locations
Any other suggestions on what to try?
First button click:
private async Task getFile()
{
FileOpenPicker openPicker = new FileOpenPicker();
openPicker.ViewMode = PickerViewMode.List;
openPicker.SuggestedStartLocation = PickerLocationId.DocumentsLibrary;
openPicker.FileTypeFilter.Add(".txt");
StorageFile file = await openPicker.PickSingleFileAsync();
if (file != null)
{
fullFilePath.Text = file.Path;
}
else
{
updateStatus("File Selection cancelled.");
}
}
Second button start this but needs to use the file from above
private async Task processFile()
{
...
string content = await FileIO.ReadTextAsync(file);
...
}

Make the StorageFile a field in your class:
class MyClass
{
StorageFile m_pickedFile;
async Task GetFile()
{
// Setup the picker...
m_pickedFile = await openPicker.PickSingleFileAsync();
// Show the path to the user...
}
async Task ProcessFile()
{
if (m_pickedFile != null)
{
// now use m_pickedFile...
}
}
}

How to copy .png using FileSavePicker for wp 8.1

How to copy *.png from appdata:/assets/images using FileSavePicker. I find this example File Save Picker - Save Edited Image (C# Metro app) but it does not work.
i have this code:
private async void OpenButton_Click(object sender, RoutedEventArgs e)
{
string path = #"\Assets\Logo.png";
StorageFolder folder = Windows.ApplicationModel.Package.Current.InstalledLocation;
StorageFile file = await folder.GetFileAsync(path);
// Show the picker
FileSavePicker savePicker = new FileSavePicker();
// Set the file that will be saved
savePicker.SuggestedSaveFile = file;
savePicker.SuggestedFileName = "Logo";
savePicker.FileTypeChoices.Add("PNG", new List<string>() { ".png" });
savePicker.PickSaveFileAndContinue();
}
but he saves the file to 0 bytes

Did you try out the sample from msdn? Where did you go wrong withe one you found?
FileSavePicker savePicker = new FileSavePicker();
savePicker.SuggestedStartLocation = PickerLocationId.DocumentsLibrary;
// Dropdown of file types the user can save the file as
savePicker.FileTypeChoices.Add("Plain Text", new List<string>() { ".txt" });
// Default file name if the user does not type one in or select a file to replace
savePicker.SuggestedFileName = "New Document";
Source:
Reference from MSDN
Save image in windows phone 8.1 using FileSavePicker

How do I save an image url to a local file in Windows 8 c#

Basically, the app displays images, and I want the user to be able to select an image for download and store it locally.
I have the URL, but I don't know how to use that url in conjunction with the filepicker.

You can use the following method to download the file from a given Uri to a file selected with a file picker:
private async Task<StorageFile> SaveUriToFile(string uri)
{
var picker = new FileSavePicker();
// set appropriate file types
picker.FileTypeChoices.Add(".jpg Image", new List<string> { ".jpg" });
picker.DefaultFileExtension = ".jpg";
var file = await picker.PickSaveFileAsync();
using (var fileStream = await file.OpenStreamForWriteAsync())
{
var client = new HttpClient();
var httpStream = await client.GetStreamAsync(uri);
await httpStream.CopyToAsync(fileStream);
fileStream.Dispose();
}
return file;
}

I think you can always read the file as a stream and save it bit by bit on the local machine. But I need to say that I've done this many times in JAVA, I never needed to check this in C# :)

SaveFileDialog myFilePicker = new SaveFileDialog();
//put options here like filters or whatever
if (myFilePicker.ShowDialog() == DialogResult.OK)
{
WebClient webClient = new WebClient();
webClient.DownloadFile("http://example.com/picture.jpg", myFilePicker.SelectedFile);
}