Save changes in file in Windows Store app in required directory

Question

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?

Answer 1

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.