Question

When a field is used for creating another field, and then disposed – I see two options. First:

Image image = Image.FromFile(path);
Bitmap bitmap = (Bitmap)image.GetThumbnailImage(32, 32, null, new IntPtr());
image.Dispose();//not needed anymore.

//use bitmap

bitmap.Dispose();

Second:

using (Image image = Image.FromFile(path))
{
    using (Bitmap bitmap = (Bitmap)image.GetThumbnailImage(32, 32, null, new IntPtr()))
    {
        //use bitmap
    }
}

The logical one would be the first (because the Image isn’t needed when the Bitmap is used), but using statements are generally preferable over Dispose.

Is there a third way – to terminate the first using inside the second one?

Answer 1

Yes, there is: Put the code to produce the thumbnail image into a method:

Bitmap GetThumbnail(string path)
{
    using (Image image = Image.FromFile(path))
    {
        return (Bitmap)image.GetThumbnailImage(32, 32, null, new IntPtr());
    }
}

// ...

using (Bitmap bitmap = GetThumbnail(path))
{
    //use bitmap
}

Please note:
I agree with Oded’s comments. I would use this code not because it disposes image first, but because it is more readable.