How to save a file from a windows store app in Unity - serialization

Question

I'm making an app in Unity3D for release on the windows store.
It seems you cant write files using the .net streamwriter.
I'd like to save a csv file to a certain location and then later send it to a server using the WWW class.
I found a project which reads a file from the assets folder.
Heres the code for that...
using UnityEngine;
using System;
using System.Collections;
using System.IO;
#if NETFX_CORE
using System.Text;
using System.Threading.Tasks;
using Windows.Storage;
using Windows.Storage.Streams;
#endif
namespace IOS
{
public class File
{
public static object result;
#if NETFX_CORE
public static async Task<byte[]> _ReadAllBytes(string path)
{
StorageFile file = await StorageFile.GetFileFromPathAsync(path.Replace("/", "\\"));
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;
}
#endif
public static IEnumerator ReadAllText(string path)
{
#if NETFX_CORE
Task<byte[]> task = _ReadAllBytes(path);
while (!task.IsCompleted)
{
yield return null;
}
UTF8Encoding enc = new UTF8Encoding();
result = enc.GetString(task.Result, 0, task.Result.Length);
#else
yield return null;
result = System.IO.File.ReadAllText(path);
#endif
}
}
}
public class Example : MonoBehaviour
{
private string data;
IEnumerator ReadFile(string path)
{
yield return StartCoroutine(IOS.File.ReadAllText(path));
data = IOS.File.result as string;
}
public void OnGUI()
{
string path = Path.Combine(Application.dataPath, "StreamingAssets/Data.txt");
if (GUILayout.Button("Read file '" + path + "'"))
{
StartCoroutine(ReadFile(path));
}
GUILayout.Label(data == null ? "<NoData>" : data);
}
}
Heres the MSDN docs for serializing with Windows Store apps
https://msdn.microsoft.com/en-us/library/windows/apps/xaml/hh758325.aspx
I'm wondering how to adapt this to suit my purposes. ie. Write a file to a specific location that I can reference later when I am sending the file via WWW.

Answer 1

The main issue is the location. The Application.dataPath is read only data within the app's package. To write data use Application.persistentDataPath to get a writable location in the application data folder.
Unity provides alternatives to System.IO.File with its UnityEngine.Windows.File object. You can just switch the using between System.IO and UnityEngine.Windows then call File.ReadAllBytes or File.WriteAllBytes regardless of platform.
This is essentially what your code snippit is doing, except that Unity already provides it.