Deleting a bitmap from local directory

Question

Alright it has come to this. I searched this website among many others and no one can seem to give me a straight answer so I'm going to try just asking outright. Been on this issue for about a solid 3 days and I can't afford to waste any more time on it.

Goal: The app I am building is in WPF and is going to be used as a bug tracker for a project my design team and I will be undertaking soon. Since we are going to be building a game in C++ most of the errors that occur will have a visual element to them so I inlcuded functionality to provide an image of the error in question when the user adds a bug to the list. I then take that image and save it to a local directory (for testing). Now the image path in the Error object points to a path that leads to the local directory. This functionality has been tested and works fine. My problem showes up when I want to delete a bug from the list. I am getting that very infamous "IO Exception" saying that the image I want to delete is being used by another process.

So Far: At first I tried very elegant solutions, but as with all things you get to a point where you just want to see if you can get the thing to even work at all. So I am at the point where most of the code I am using is experimental and radical. So please when looking at it note that the code being used is out of desperation, so any "simple" solutions have probably already been tried (I did research this a lot becuase I hate having to do this). Things i can think of off the top of my head are the obsurd amount of disposes and forced garbage collections being called so please to not comment on the negative nature of this practice, I am well aware :).

The Code

Saving image to local directory

public void OnBrowseClick()
    {
        Microsoft.Win32.OpenFileDialog openBox = new Microsoft.Win32.OpenFileDialog();

        // Show dialog box to user and grab output
        Nullable<bool> result = openBox.ShowDialog();

        if (result == true)
        {
            // Create temp variable to hold local path string
            string localPath = Directory.GetCurrentDirectory();      

            // Grab the extension of the specified file path
            string extension = openBox.FileName.Substring(openBox.FileName.LastIndexOf("\\"));

            // Add extension to local path
            localPath += extension;

            // Create local copy of image at given file path (being ridiculous at this point)
            using (Stream stream = new FileStream(openBox.FileName, FileMode.Open, FileAccess.ReadWrite))
            {
                using (Bitmap bmp = LoadImage(stream))
                {
                    using (Bitmap temp = (Bitmap)bmp.Clone())
                    {
                        temp.Save(localPath);
                        temp.Dispose();
                    }

                    bmp.Dispose();
                }

                stream.Dispose();
            }

            // Set the URL in the image text box (UI stuff)
            LocalError.ImagePath = localPath;   
        }
    }

The following is the LoadImage function that is used in the function above

private Bitmap LoadImage(Stream stream)
    {
        Bitmap retval = null;

        using (Bitmap bitmap = new Bitmap(stream))
        {
            retval = new Bitmap(bitmap.Width, bitmap.Height, bitmap.PixelFormat);

            using (Graphics gdi = Graphics.FromImage(retval))
            {
                gdi.DrawImageUnscaled(bitmap, 0, 0); 
                gdi.Flush();
                gdi.Dispose();
                bitmap.Dispose();
            }
        }

        // Garbage collection here to be safe
        GC.WaitForPendingFinalizers();
        GC.Collect();

        return retval;
    } 

And finally we come to where I try to delete the image

public void OnDeleteClick()
    {
        // Ask user to make sure they want to delete selected item(s)
        MessageBoxResult result = MessageBox.Show("Are you sure you want to delete selected item(s) from the list?",
                                "Delete", MessageBoxButton.YesNo);

        if (result == MessageBoxResult.Yes)
        {
            for( int i = 0; i < Parent.ErrorListControl.ErrorDataGrid.SelectedItems.Count; ++i)
            {
                // Get path to image
                string path = (Parent.ErrorListControl.ErrorDataGrid.SelectedItems[i] as Error).ImagePath;

                // Even tried calling garbage collection here!!!!!
                System.GC.WaitForPendingFinalizers();
                System.GC.Collect();
                File.Delete(path);

                // Remove the error from the error list
                Parent.ErrorListVM.ErrorList.Remove((Error)Parent.ErrorListControl.ErrorDataGrid.SelectedItems[i]);

                // Decrement counter because we altered the list while in a loop
                i--;
            }
        }
    }

Notes: If anyone would like me to explain anything further or if you need to know something I left out please just ask I will get back to you ASAP! Any suggestions are helpful at this point I have absolutley no idea what I am doing wrong. I generally only program in a C++ environment so I tend to manage my own memory this whole "garbage collection" thing is really throwing a wrench in our project! (Off topic note: I do not know why I am not getting any color highlighting so I apologize to anyone who takes the time to read this).

Answer 1

Since your LoadImage method does simple copy of the image, why not use File.Copy(source, dest) and avoid all the bitmaps, drawings, etc? Your goal might be to modify local bitmap after it's created, but it can still be done after copy.

Also, when using the using block, explicit .Dispose() is not required, as using block does it for you:

using (var obj = new SomeDisposableObject())
{
    // code here
    // obj.Dispose(); <-- not needed, since...
} // ...at this point obj.Dispose is called automatically.

Answer 2

Here's a simple way to do what you want. In this example, I'm using Path.GetTempFileName() to generate a random file name in the local user's temp directory. If you don't need to persist the files then it's a good place to store them temporarily. Also, the user could theoretically import two files with the same name. So you want to use some kind of random filename generation or other mechanism to avoid conflicts.

private void browseButton_Click(object sender, RoutedEventArgs e)
{
    var openFileDialog = new Microsoft.Win32.OpenFileDialog();

    if (openFileDialog.ShowDialog(this) == true)
    {
        using (Bitmap originalImage = new Bitmap(openFileDialog.FileName))
        {
            string tempFileName = System.IO.Path.GetTempFileName();

            originalImage.Save(tempFileName);

            // LocalError.LocalPath
            LocalPath = tempFileName;
        }
    }
}

private void deleteButton_Click(object sender, RoutedEventArgs e)
{
    if (File.Exists(LocalPath))
    {
        File.Delete(LocalPath);
    }
}

Although a simple File.Copy should suffice as long as you have the right paths, I was just providing a solution that matched your question.

EDIT: Actually the current directory does not seem to be changed by the OpenFileDialog. I could swear that it did at some point. So I don't think this is your problem. Regardless, this code still works for me and you shouldn't require anything more complicated than this.

EDIT #2: It seems the lock is actually caused by the image being databound to the view and presumably locked by the BitmapSource. You should be able to create it without locking the file. Generally, this is slower so don't do it this way unless you need to be able to modify or delete the file.

bitmapSource = new BitmapImage();
bitmapSource.BeginInit();
bitmapSource.CacheOption = BitmapCacheOption.OnLoad;
bitmapSource.CreateOption = BitmapCreateOptions.IgnoreImageCache;
bitmapSource.UriSource = new Uri(ImagePath, UriKind.Absolute);
bitmapSource.EndInit();