IsolatedStorageException exception even if it has passed File.Exists Test

Questions & Answers
1

i have developed a simple android game in unity3d, i want to read a file which is created by myself. it is a simple config file. exception call stack:

IsolatedStorageException: Could not find a part of the path "/storage/emulated/0/Android/data/com.Test.Demo/files/basic.cfg".
07-16 12:04:35.905  4248  5019 I Unity   :   at System.IO.FileStream..ctor (System.String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, Boolean anonymous, FileOptions options) [0x00000] in <filename unknown>:0 
07-16 12:04:35.905  4248  5019 I Unity   :   at System.IO.FileStream..ctor (System.String path, FileMode mode, FileAccess access, FileShare share) [0x00000] in <filename unknown>:0 
07-16 12:04:35.905  4248  5019 I Unity   :   at System.IO.File.OpenRead (System.String path) [0x00000] in <filename unknown>:0 
07-16 12:04:35.905  4248  5019 I Unity   :   at System.IO.File.ReadAllBytes (System.String path) [0x00000] in <filename unknown>:0 
07-16 12:04:35.905  4248  5019 I Unity   :   at FileManager.ReadFile (System.String filePath) [0x00000] in <filename unknown>:0

this is my read file code.

public static byte[] ReadFile(string filePath)
{
    if (!System.IO.File.Exists(filePath))
    {
        return null;
    }

    return System.IO.File.ReadAllBytes(filePath);
}

this is my code. the exception message is :

IsolatedStorageException: Could not find a part of the path “/storage/emulated/0/Android/data/com.Test.Demo/files/basic.cfg”.

i can’t understand that why the ReadAllBytes method throw this exception, even if it is passed by File.Exists test.

this is the code i find in unity.mono:

 public static FileStream OpenRead (string path)
        {
            return new FileStream (path, FileMode.Open, FileAccess.Read, FileShare.Read);
        }

        //
        // The documentation for this method is most likely wrong, it
        // talks about doing a "binary read", but the remarks say
        // that this "detects the encoding".
        //
        // This can not detect and do anything useful with the encoding
        // since the result is a byte [] not a char [].
        //
        public static byte [] ReadAllBytes (string path)
        {
            using (FileStream s = OpenRead (path)) {
                long size = s.Length;
                // limited to 2GB according to http://msdn.microsoft.com/en-us/library/system.io.file.readallbytes.aspx
                if (size > Int32.MaxValue)
                    throw new IOException ("Reading more than 2GB with this call is not supported");

                int pos = 0;
                int count = (int) size;
                byte [] result = new byte ;
                while (count > 0) {
                    int n = s.Read (result, pos, count);
                    if (n == 0)
                        throw new IOException ("Unexpected end of stream");
                    pos += n;
                    count -= n;
                }
                return result;
            }
        }

this is my manifest.xml permission configuration:

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
    <uses-permission android:name="android.permission.GET_TASKS" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
    <uses-permission android:name="android.permission.READ_PHONE_STATE" />
    <uses-permission android:name="android.permission.RESTART_PACKAGES" />
    <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

not all of them.

and this exception is not throw every times. sometimes it throw this exception.

2

Because we can only use WWW to read files on Android Platform.