C# Waiting for an operation to complete prior to deleting a file

Question

My delete call does not work because the files in the directory are read only (still being accessed) when called. How do I wait until the file has been processed and released by the tesseract engine to delete it?

I have tried a while loop at the "delete" call waiting for an exception NOT to be thrown - this just hangs. I've seen examples using Tasks, Threads, and Processes. What it is programmatically the right way to do this?

        // create a subdirectory called processing
        Directory.CreateDirectory(dir + "//processing");
        string directory = dir + "//processing";

        // extract the images to the processing directory
        ImageExtractor.ExtractImagesFromFile(LongName, "img", directory, true);

        // extract the text from all the files in processing
        string[] images = Directory.GetFiles(directory);
        foreach (string file in images)
        {
            Bitmap image = new Bitmap(file);
            using (TesseractEngine engine = new TesseractEngine(@"./tessdata", "eng", EngineMode.Default))
            {
                using(var img = PixConverter.ToPix(image))
                {
                    using(var page = engine.Process(img))
                    {
                        fileContent = fileContent + " " + page.GetText();
                    }
                }
            }
        }

        Directory.Delete(dir + "//processing", true);

Using a task... (does not work for me)...

Task t = Task.Run(() => { 
            foreach (string file in images)
            {
                Bitmap image = new Bitmap(file);
                using (TesseractEngine engine = new TesseractEngine(@"./tessdata", "eng", EngineMode.Default))
                {
                    using(var img = PixConverter.ToPix(image))
                    {
                        using(var page = engine.Process(img))
                        {
                            fileContent = fileContent + " " + page.GetText();
                        }
                    }
                }
            }
            });

            t.Wait();

            Directory.Delete(dir + "//processing", true);