EF Core 3.1 Beta Can't save images in DB

The code works with EF6 and Oracle.ManagedDataAccess.EntityFramework.

With Core 3.1 the following error occurs by saving the context:

An error occurred while updating the entries. See the inner exception for details.

OracleException: ORA-01460: Nicht implementierte oder nicht sinnvolle Umwandlung gefordert

My DB-Set for the images looks like this:

    public class Picture

    {

        public int PictureID { get; set; }

        public byte[] Bild { get; set; }

        public DateTime Ludsys { get; set; }

        public int OrderDetailID { get; set; }

        public OrderDetail OrderDetail { get; set; } // Navigationseigenschaft

    } // Picture

When I call "Add-Migration" und "Update-DataBase" at the PM-Console the System generates for the byte-array a Column of type RAW instead of BLOB.

Code in .xaml File:

            <Image Name="imgBild" Source="{Binding Bild, Converter={StaticResource PhotoConverter}, Mode=TwoWay}" Grid.Row="2"

                   Height="400" Margin="10,0" HorizontalAlignment="Left" Stretch="Uniform"/>

Code in .xaml.cs File:

                     ...

                    picture = new Picture

                   {

                        Bild = null,

                        Ludsys = DateTime.Now,

                        OrderDetail = orderdetail

                    }; // picture

                    imgBild.DataContext = picture;

                    imgBild.Source = FileToBitmapImage(dlg.FileName); // Bild aus Filesystem laden und anzeigen

                    context.Pictures.Add(picture);

                    pictures.Add(picture);

                    ind = pictures.Count - 1; // Index für den neuen Datensatz ist pictures.Count - 1

                    ...

        private BitmapImage FileToBitmapImage(string source)

        {

            try

            {

                if (source == string.Empty) { return null; }

                BitmapImage bitmapimage = new BitmapImage();

                using (FileStream filestream = File.Open(source, FileMode.Open))

                {

                    bitmapimage.BeginInit();

                    bitmapimage.CacheOption = BitmapCacheOption.OnLoad;

                    bitmapimage.StreamSource = filestream;

                    bitmapimage.EndInit();

                    return bitmapimage;

                } // using

            } // try

            catch (Exception ex)

            {

                MessageBox.Show(ex.Message, "Nachricht", MessageBoxButton.OK, MessageBoxImage.Error);

                return null;

            } // catch

        } // FileToBitmapImage

Code of Converter:

    class PhotoConverter : IValueConverter

    {

        // Convert (Quelle -> Ziel)

        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)

        {

            try

            {

                if (value == null) { return null; }

                byte[] byteArray = (byte[])value;

                using (MemoryStream memorystream = new MemoryStream(byteArray))

                {

                    BitmapImage bitmapimage = new BitmapImage();

                    bitmapimage.BeginInit();

                    bitmapimage.CacheOption = BitmapCacheOption.OnLoad;

                    bitmapimage.StreamSource = memorystream;

                    bitmapimage.EndInit();

                    return bitmapimage;

                } // using

            } // try

            catch (Exception)

            {

                return null;

            } // catch

        } // Convert

        // ConvertBack (Ziel -> Quelle)

        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)

        {

            try

            {

                if (value == null) { return null; }

                ImageSource imagesource = (ImageSource)value;

                BitmapSource bitmapsource = imagesource as BitmapSource;

                BitmapEncoder encoder = new JpegBitmapEncoder();

                encoder.Frames.Add(BitmapFrame.Create(bitmapsource));

                using (MemoryStream ms = new MemoryStream())

                {

                    encoder.Save(ms);

                    byte[] bytearray = ms.ToArray();

                    return bytearray;

                } // using

            } // try

            catch (Exception)

            {

                return null;

            } // catch

        } // ConvertBack

    } // PhotoConverter