WPF как очистить Source у Image Control

Нюанс в том, что XAML кэширует все изображения, не спрашивая на это разрешения. Чтобы избавиться от блокировки файла, нужно создать BitmapImage с CacheOption равным BitmapCacheOption.OnLoad. Сделать это можно либо напрямую в коде, и тогда забиндиться уже не на string, а на BitmapImage, либо с помощью конвертера.

Вот конвертер, написанный Kent Boogaart:

/// <summary>
/// This converter facilitates a couple of requirements around images. Firstly, it automatically disposes of image streams as soon as images
/// are loaded, thus avoiding file access exceptions when attempting to delete images. Secondly, it allows images to be decoded to specific
/// widths and / or heights, thus allowing memory to be saved where images will be scaled down from their original size.
/// </summary>
public sealed class BitmapFrameConverter : IValueConverter
{
    //doubles purely to facilitate easy data binding
    private double _decodePixelWidth;
    private double _decodePixelHeight;
    public double DecodePixelWidth
    {
        get
        {
            return _decodePixelWidth;
        }
        set
        {
            _decodePixelWidth = value;
        }
    }
    public double DecodePixelHeight
    {
        get
        {
            return _decodePixelHeight;
        }
        set
        {
            _decodePixelHeight = value;
        }
    }
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        string path = value as string;
        if (path != null)
        {
            //create new stream and create bitmap frame
            BitmapImage bitmapImage = new BitmapImage();
            bitmapImage.BeginInit();
            bitmapImage.StreamSource = new FileStream(path, FileMode.Open, FileAccess.Read);
            bitmapImage.DecodePixelWidth = (int) _decodePixelWidth;
            bitmapImage.DecodePixelHeight = (int) _decodePixelHeight;
            //load the image now so we can immediately dispose of the stream
            bitmapImage.CacheOption = BitmapCacheOption.OnLoad;
            bitmapImage.EndInit();
            //clean up the stream to avoid file access exceptions when attempting to delete images
            bitmapImage.StreamSource.Dispose();
            return bitmapImage;
        }
        else
        {
            return DependencyProperty.UnsetValue;
        }
    }
    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return DependencyProperty.UnsetValue;
    }
}

См. Delete image file used by XAML.

Решил так. Сохраняю картинку с рандомным именем в папку Temp

private void LoadImageFromDataBase(byte[] image)
    {
        using (var ms = new MemoryStream(image))
        {
            var photo = System.Drawing.Image.FromStream(ms);
            string randomFileName = Path.GetRandomFileName();
            randomFileName = randomFileName.Replace(".", "");
            var path = Environment.CurrentDirectory + "\\Temp\\" + randomFileName + ".png";
            photo.Save(path);
            Photo = path;
        }
    }

А при закрыти программы удаляю папку Temp и заново создаю ее

string dir = System.Environment.CurrentDirectory + "\\Temp";
System.IO.Directory.Delete(dir, true);
System.IO.Directory.CreateDirectory(dir);