operation not permitted on isolatedstoragefilestream all the time - windows-phone-8

Question

there was a lot of question about this error, but i couldn't find the problem i'm facing with it.
I have 2 buttons: 1 to save some string into the isolatedStorage, and 1 to read it.
when i try to read it i get the errorMessage written in the title.
Button1.Click is:
using (var store = IsolatedStorageFile.GetUserStoreForApplication())
using (var stream = new IsolatedStorageFileStream("kedvencek" + ".txt",
System.IO.FileMode.Append,
System.IO.FileAccess.ReadWrite,
store))
{
StreamWriter writer = new StreamWriter(stream);
writer.WriteLine("something");
writer.Close();
stream.Close();
}
and the Button 2:
using (var store = IsolatedStorageFile.GetUserStoreForApplication())
using (var stream = new IsolatedStorageFileStream("kedvencek" + ".txt",
System.IO.FileMode.Open,
System.IO.FileAccess.ReadWrite,
store))
{
StreamReader sr = new StreamReader(stream);
string text = sr.ReadToEnd();
MessageBox.Show(text);
sr.Close();
stream.Close();
}

Answer 1

The problem you are facing is connected with the fact that as MSDN says::
FileMode.Append can only be used in conjunction with Write.
So it will work if you had changed it to:
using (var stream = new IsolatedStorageFileStream("kedvencek" + ".txt",
FileMode.Append, FileAccess.Write, store))
On the other hand you don't need to close stream when you have it in using(), after leaving using() the steream is Disposed automatically. And it will better to put StreamWriter also into using():
private void first_Click(object sender, RoutedEventArgs e)
{
using (var store = IsolatedStorageFile.GetUserStoreForApplication())
using (var stream = new IsolatedStorageFileStream("kedvencek" + ".txt", FileMode.Append, FileAccess.Write, store))
using (StreamWriter writer = new StreamWriter(stream))
{
writer.WriteLine("something");
}
}
private void second_Click(object sender, RoutedEventArgs e)
{
using (var store = IsolatedStorageFile.GetUserStoreForApplication())
using (var stream = new IsolatedStorageFileStream("kedvencek" + ".txt", FileMode.Open, FileAccess.ReadWrite, store))
using (StreamReader sr = new StreamReader(stream))
{
string text = sr.ReadToEnd();
MessageBox.Show(text);
}
}