CODEWITHSUNDEEP
c#windows-phone-7
Rakesh R Nair
Rakesh R Nair

Reputation: 1785

Error occurs while trying to write an image in to Isolated Storage in WP7 Mango

Here i am attaching the code snippet.

Error is: An error occurred while accessing IsolatedStorage.

public Boolean SaveImage(string filename, WriteableBitmap wrtbmp)
{
    try
    {
        using (IsolatedStorageFile iSF = IsolatedStorageFile.GetUserStoreForApplication())
        {
            if (iSF.FileExists(filename))
            {
                iSF.DeleteFile(filename);
            }
            using (IsolatedStorageFileStream fstream = new IsolatedStorageFileStream(filename, FileMode.CreateNew, FileAccess.Write, iSF))
            {
                wrtbmp.SaveJpeg(fstream, wrtbmp.PixelWidth, wrtbmp.PixelHeight, 0, 100);
                fstream.Close();
                fstream.Dispose();
            }
        }
    }
    catch (Exception ex)
    {
        if (System.Diagnostics.Debugger.IsAttached)
        {
            System.Diagnostics.Debugger.Break();
        }
        return false;
    }

    return true;
}

This is the method i am using for saving Image, while executing when it reaches the portion of deleting the file if it already exists, it throws the error, but in some cases it executes perfectly without an error.

Upvotes: 1

Views: 331

Answers (2)

quetzalcoatl
quetzalcoatl

Reputation: 33506

The stacktrace points to the DeleteFile. Are you sure the path-to-delete is valid? Are you sure that the file exists? I don't remember well, but I think the Delete file might throw if the file is not found - please check the example in the linked MSDN method description - they have an IF-exists there. [EDIT: I'm sorry, I'm quite a bit tired today and I didn't read through your code properly. Obviously you have your code already guarded against file-nonexistence.]

Aside from the possible nonexistence problem, there is also a small possibility that ont here, but somewhere else in your code, there is something that has opened the file and did not close it properly. In such case, the system will think the file is in use (even if that "old" handle opened elsewhere is "forgotten" and wait to be GC'ed) and no operations on that file will succeed unles that handle actually dies.

Another thing is, that even with your using/autodispose, the operation can still fail if you try to invoke the method multiple times at once from different threads. With async patterns, it sometimes can be hard to notice - check thoroughly from what points of code this method is called and think whether it may happen ie. that at the same time GUI callback will invoke it, and maybe also some background operation? If so, try to wrap the using additionally with a lock-statement. If this helps, that means you have reentrancy problems.

edit: someone, at some point in distant future, will kill me for hundrets of edits.. but I'll write it anyways:) : I think that in general, you do not have to delete the file before writing to it. The CreateFile is not the only one to get access to the files. Check OpenFile with mode=OpenOrCreate|Truncate or even shorter: mode=Create (see FileMode flags for explanation)

Upvotes: 1

Claus Jørgensen
Claus Jørgensen

Reputation: 26347

First of all, there's no reason to call fstream.Close(); and fstream.Dispose(); when you're using a using statement, which automatically closes and disposes of the stream.

Secondly, your error isn't explicit enough.

Upvotes: 1

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