Isolated Storage - strange error with Exception

Question

I try save picture in IsolatedStorage on my Device. I turn OFF the internet and tap the button in my application. At the first time, exception is appears correctly: "The remote server returned an error: NotFound."

the next step: I turn ON the internet and tap the button - the image is saved on my phone. Everything is ok.

And now is the most important thing: when I again turn off the internet i will never see again this exception (if i want see I must uninstall, and install app again)

Why?

p.s: sorry for my english

public void update()
{
    WebClient client = new WebClient();
    client.OpenReadCompleted += new OpenReadCompletedEventHandler(client_OpenReadCompleted);
    client.OpenReadAsync(new Uri(@"http://www.myurl.com/" + path + "/" + number.ToString() + ".jpg"), client);
}

void client_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
{
    try
    {
        var resInfo = new StreamResourceInfo(e.Result, null);
        var reader = new StreamReader(resInfo.Stream);
        byte[] contents;

        using (BinaryReader bReader = new BinaryReader(reader.BaseStream))
        {
            contents = bReader.ReadBytes((int)reader.BaseStream.Length);
        }

        if (!MyStore.DirectoryExists(path))
            MyStore.CreateDirectory(path);

        IsolatedStorageFileStream stream = MyStore.CreateFile(path +"/"+ number.ToString() + ".jpg");
        stream.Write(contents, 0, contents.Length);
        stream.Close();
    }

    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }

}

Answer 1

Your image has been cached after the first request and all other requests will try to get the file from the cache first and if the file has been found - no requests to the internet will be made.

If you want to avoid it:

1) At your own server with files you can modify Cache-Control: max-age header value to some time when image can be cached.

2) Build unique request URI for the each request like client.OpenReadAsync(new Uri(@"http://www.myurl.com/" + path + "/" + number.ToString() + ".jpg" + "?rand=" + GetRandomNumber()), client);