Develop Reference

Xamarin Could not find a part of the path

I am trying to save a bitmap to the Android storage.
My code looks like this:
var folderPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
var filePath = System.IO.Path.Combine(folderPath, "Pictures/profile_picture.png");
var stream = new FileStream(filePath, FileMode.Create);
bitmap.Compress(Bitmap.CompressFormat.Png, 100, stream);
stream.Close();
But the application enters break mode and it says:
System.IO.DirectoryNotFoundException: Could not find a part of the path.
Any help is appreciated.
Thanks in advance, Zoedingl.

"Pictures" directory is not created. So, you are getting "Could not find a part of the path" error. Change code as below or you can create directory for "Pictures" then use same code should work.
var filePath = System.IO.Path.Combine(folderPath, "profile_picture.png");
Code for creating directory
Directory.CreateDirectory(System.IO.Path.Combine(folderPath, "Pictures"));

Convert StorageFile to string

We need to store an image file as a string in a UWP app. This was the plan:
FileOpenPicker picker = new FileOpenPicker();
picker.FileTypeFilter.Add(".png");
StorageFile file = await picker.PickSingleFileAsync();
byte[] fileBytes = File.ReadAllBytes(file.Path);
string fileString = Convert.ToBase64String(fileBytes);
but the line
byte[] fileBytes = File.ReadAllBytes(file.Path);
throws
System.UnauthorizedAccessException Access to the path 'C:\MyFolder\ImageFile.png' is denied.
For this exercise Everyone has Full Control permission on the file. I've also moved the file to various locations including a USB stick but always get the same exception. I assume this is a UWP thing rather than a permissions thing?
How do we save an image file as a string in a UWP app?

You get the exception, because in UWP you only can access to files over the path, is in the App-Package area.
To solve your problem you can use the IBuffer extension ToArray:
IBuffer buffer = await FileIO.ReadBufferAsync(file);
string fileString = Convert.ToBase64String(buffer.ToArray());

you can't directly access to a file with string path. In UWP, you should always access file with Storage(File, Folder)check this
to get Bytes, you can use FileIO class or Open Stream with StorageFile.

Access file from the app folder in uwp

Directory:
App1
- MainPage.xaml.cs
- Sample.xaml
im trying to do is getting the xaml content from the sample as a string but it doesnt work since it cant find the file:
var x = Path.GetFullPath(#"sample.xaml");
FileStream s = new FileStream(x, FileMode.Open);
How can I fix this?

I haven't tried this give it a try.
Save your file in a location eg (Assets Folder)Now, make sure that the
build action is set to Content.
var storageFile = await StorageFile.GetFileFromApplicationUriAsync(
new Uri("ms-appx:///Assets/youfile.xaml"));
The StorageFile you get is of course read-only, but it can be passed to any API that expects a StorageFile.
If you want to read you can try.
var result = storageFile.OpenReadAsync()
StorageFile Documentation

The source files (.xaml, .cs) are compiled, and in the deployed app they do not exist as physical files, so you can't open them this way.

Error when using Bitmap.SetSource

I'm working on an app which loads images from a chosen folder to a gridView.
when I use SetSource to set the BitmapImage source I receive an error "insufficient memory" after loading some of the images.
when I use the constructor with a Uri path it works fine. but it will only display images from the projects directory.
StorageFolder folder = await StorageApplicationPermissions.FutureAccessList.GetFolderAsync(RecentToken);
StorageFile file = await folder.GetFileAsync(path);
IRandomAccessStream stream = await file.OpenReadAsync();
image = new BitmapImage(new Uri(file.Path));//loads only within project directory
image.SetSource(stream);//causes insufficient memory
stream.Dispose();

Found the solution!
I set the BitmaPimage's DecodePixelHeight to the size of the Displayed image and it works fine now!

Save changes in file in Windows Store app in required directory

using c#, VS2013, windows store app
In simple program have a file with some data saved in JSON format. I'll try to add new data to this file and then store it.
Try to save file in JSON with next code:
string result = await JsonConvert.SerializeObjectAsync(groups);
//get file path
string pathOfFile = Path.GetDirectoryName(file.Path); //get path
StorageFolder folder = await StorageFolder.GetFolderFromPathAsync(pathOfFile); //create dir by path
StringBuilder builder = new StringBuilder();
builder.Append(folder.Path);
builder.Append("\\EventsData.json");
Uri uriToSave = new Uri(builder.ToString());
//create file
StorageFile fileToWrite =
await StorageFile.GetFileFromApplicationUriAsync(uriToSave);
using (IRandomAccessStream stream =
await file.OpenAsync(FileAccessMode.ReadWrite))
{
// write the JSON file
using (DataWriter textWriter = new DataWriter(stream))
{
textWriter.WriteString(result);
await textWriter.StoreAsync();
}
}
But during executing code StorageFile fileToWrite = await StorageFile.GetFileFromApplicationUriAsync(uriToSave); got exception System.ArgumentException
During debagging got next Uri
Question - why i got such exception and if I'm wrong - how to save file in windows store app in required directory?
Also look MSDN sample for writing data to file, and use code like in tutorial but got System.UnauthorizedAccessException:
StorageFile sampleFile = await folder.CreateFileAsync("EventsData.json", CreationCollisionOption.ReplaceExisting);
await Windows.Storage.FileIO.WriteTextAsync(sampleFile, result);
Why Access denied or I missing something?

You cannot write to the install directory without explicit permission from the user.
Here is the protocol instead:
At first startup, check to see if there is a file in the local data folder (ApplicationDataContainer), if not, read in the file from the install directory.
Write out a copy of the file to the local app data folder (Check out guides on ApplicationDataContainer for more info there)
Edit this file freely.