UWP apps accessing files from random location on s

问题:

in UWP there are files and permissions restrictions, so we can only acces files directly from few folders or we can use filepicker to access from anywhere on system. how can I use the files picked from filepicker and use them anytime again when the app runs ? tried to use them again by path but it gives permission error. I know about the "futureacceslist" but its limit is 1000 and also it will make the app slow if I am not wrong? . Is there a better way to do this ? or can we store storage files link somehow in local sqlite database?

回答1:

Considering this method..

    public async static Task<byte[]> ToByteArray(this StorageFile file)
    {
        byte[] fileBytes = null;
        using (IRandomAccessStreamWithContentType stream = await file.OpenReadAsync())
        {
            fileBytes = new byte[stream.Size];

            using (DataReader reader = new DataReader(stream))
            {
                await reader.LoadAsync((uint)stream.Size);
                reader.ReadBytes(fileBytes);
            }
        }

        return fileBytes;
    }

This class..

    public class AppFile
    {
        public string FileName { get; set; }
        public byte[] ByteArray { get; set; }
    }

And this variable

    List<AppFile> _appFiles = new List<AppFile>();

Just..

    var fileOpenPicker = new FileOpenPicker();
    IReadOnlyList<StorageFile> files = await fileOpenPicker.PickMultipleFilesAsync();

    foreach (var file in files)
    {
        var byteArray = await file.ToByteArray();
        _appFiles.Add(new AppFile { FileName = file.DisplayName, ByteArray = byteArray });
    }

UPDATE

using Newtonsoft.Json;
using System.Linq;
using Windows.Security.Credentials;
using Windows.Storage;

namespace Your.Namespace
{
    public class StateService
    {
        public void SaveState<T>(string key, T value)
        {
            var localSettings = ApplicationData.Current.LocalSettings;
            localSettings.Values[key] = JsonConvert.SerializeObject(value);
        }

        public T LoadState<T>(string key)
        {
            var localSettings = ApplicationData.Current.LocalSettings;
            if (localSettings.Values.ContainsKey(key))
                return JsonConvert.DeserializeObject<T>(((string)    localSettings.Values[key]));
            return default(T);
        }

        public void RemoveState(string key)
        {
            var localSettings = ApplicationData.Current.LocalSettings;
            if (localSettings.Values.ContainsKey(key))
                localSettings.Values.Remove((key));
        }

        public void Clear()
        {
            ApplicationData.Current.LocalSettings.Values.Clear();
        }
    }
}

回答2:

If you need to access lots of files, asking the user to select the parent folder and then storing that is probably a better solution (unless you want to store 1,000 individually-picked files from different locations). You can store StorageFolders in the access list as well.

I'm not sure why you think it will make your app slow, but the only real way to know if this will affect your performance is to try it and measure against your goals.

回答3:

A bit late, but, yes the future access list will slow down your app in that it returns storagfile, storagefolder, or storeageitem objects. These run via the runtime broker which hits a huge performance barrier at about 400 objects regardless of the host capability