multiple uploading file

Hi Xamarin forum

is this correct syntax for multiple uploading mages to database

XAML

 <ScrollView>
            <StackLayout>
                <StackLayout Orientation="Horizontal">
                    <Image x:Name="imagePreview" HeightRequest="200" WidthRequest="200" />
                    <Button Text="Pick image" Clicked="Select_Pic" HeightRequest="5" WidthRequest="100"/>
                </StackLayout>
                <StackLayout Orientation="Horizontal">
                    <Image x:Name="imagePreview2" HeightRequest="200" WidthRequest="200" />
                    <Button Text="Pick image" Clicked="Select_Pic_2" HeightRequest="5" WidthRequest="100"/>
                </StackLayout>
                <StackLayout Orientation="Horizontal">
                    <Image x:Name="imagePreview3" HeightRequest="200" WidthRequest="200" />
                    <Button Text="Pick image" Clicked="Select_Pic_3" HeightRequest="5" WidthRequest="100"/>
                </StackLayout>
                <StackLayout Orientation="Horizontal">
                    <Image x:Name="imagePreview4" HeightRequest="200" WidthRequest="200" />
                    <Button Text="Pick image" Clicked="Select_Pic_4" HeightRequest="5" WidthRequest="100"/>
                </StackLayout>
                <Controls:CustomEditor Placeholder="Write a Description.." x:Name="postContent" HeightRequest="100"/>
                <Button Text="UPLOAD" Clicked="Upload_File"/>
            </StackLayout>
        </ScrollView>

Codebehind

 public partial class PostCreationPage : ContentPage
    {
        public PostCreationPage()
        {
            InitializeComponent();

        }
        private MediaFile _mediaFile;
        private MediaFile _mediaFile2;
        private MediaFile _mediaFile3;
        private MediaFile _mediaFile4;

        List<string> _images = new List<string>();

        private async void Select_Pic(object sender, EventArgs e)
        {
            string[] fileTypes = null;

            if (Device.RuntimePlatform == Device.Android)
            {
                fileTypes = new string[] { "image/jpeg" };
            }

            if (Device.RuntimePlatform == Device.iOS)
            {
                fileTypes = new string[] { "public.image" };
            }

            await CrossMedia.Current.Initialize();

            if (!CrossMedia.Current.IsPickPhotoSupported)
            {
                await DisplayAlert("Error", "Image file type not support.", "OK");
                return;
            }
            else
            {
                var mediaOption = new PickMediaOptions()
                {
                    PhotoSize = PhotoSize.Medium
                };

                _mediaFile = await CrossMedia.Current.PickPhotoAsync();

                if (_mediaFile == null) return;

                imagePreview.Source = ImageSource.FromStream(() => _mediaFile.GetStream());
                var memoryStream = new MemoryStream();
                await _mediaFile.GetStream().CopyToAsync(memoryStream);
                byte[] imageAsByte = memoryStream.ToArray();
            }
        }

        private async void Select_Pic_2(object sender, EventArgs e)
        {
            string[] fileTypes = null;

            if (Device.RuntimePlatform == Device.Android)
            {
                fileTypes = new string[] { "image/jpeg" };
            }

            if (Device.RuntimePlatform == Device.iOS)
            {
                fileTypes = new string[] { "public.image" };
            }

            await CrossMedia.Current.Initialize();

            if (!CrossMedia.Current.IsPickPhotoSupported)
            {
                await DisplayAlert("Error", "Image file type not support.", "OK");
                return;
            }
            else
            {
                var mediaOption = new PickMediaOptions()
                {
                    PhotoSize = PhotoSize.Medium
                };

                _mediaFile2 = await CrossMedia.Current.PickPhotoAsync();

                if (_mediaFile2 == null) return;

                imagePreview2.Source = ImageSource.FromStream(() => _mediaFile2.GetStream());
                var memoryStream = new MemoryStream();
                await _mediaFile2.GetStream().CopyToAsync(memoryStream);
                byte[] imageAsByte2 = memoryStream.ToArray();
            }
        }

        private async void Select_Pic_3(object sender, EventArgs e)
        {
            string[] fileTypes = null;

            if (Device.RuntimePlatform == Device.Android)
            {
                fileTypes = new string[] { "image/jpeg" };
            }

            if (Device.RuntimePlatform == Device.iOS)
            {
                fileTypes = new string[] { "public.image" };
            }

            await CrossMedia.Current.Initialize();

            if (!CrossMedia.Current.IsPickPhotoSupported)
            {
                await DisplayAlert("Error", "Image file type not support.", "OK");
                return;
            }
            else
            {
                var mediaOption = new PickMediaOptions()
                {
                    PhotoSize = PhotoSize.Medium
                };

                _mediaFile3 = await CrossMedia.Current.PickPhotoAsync();

                if (_mediaFile3 == null) return;

                imagePreview3.Source = ImageSource.FromStream(() => _mediaFile3.GetStream());
                var memoryStream = new MemoryStream();
                await _mediaFile3.GetStream().CopyToAsync(memoryStream);
                byte[] imageAsByte3 = memoryStream.ToArray();
            }
        }

        private async void Select_Pic_4(object sender, EventArgs e)
        {
            string[] fileTypes = null;

            if (Device.RuntimePlatform == Device.Android)
            {
                fileTypes = new string[] { "image/jpeg" };
            }

            if (Device.RuntimePlatform == Device.iOS)
            {
                fileTypes = new string[] { "public.image" };
            }

            await CrossMedia.Current.Initialize();

            if (!CrossMedia.Current.IsPickPhotoSupported)
            {
                await DisplayAlert("Error", "Image file type not support.", "OK");
                return;
            }
            else
            {
                var mediaOption = new PickMediaOptions()
                {
                    PhotoSize = PhotoSize.Medium
                };

                _mediaFile4 = await CrossMedia.Current.PickPhotoAsync();

                if (_mediaFile4 == null) return;

                imagePreview4.Source = ImageSource.FromStream(() => _mediaFile4.GetStream());
                var memoryStream = new MemoryStream();
                await _mediaFile4.GetStream().CopyToAsync(memoryStream);
                byte[] imageAsByte4 = memoryStream.ToArray();
            }
        }

        private async void Upload_File(object sender, EventArgs e)
        {
            if (_images == null)
            {
                await DisplayAlert("Error", "There was an error occured when trying to get your image.", "OK");
                return;
            }
            else
            {
                UploadImage(_mediaFile2.GetStream());
            }
        }

        private async void UploadImage(Stream stream)
        {
            Pipeline databaseConnect = new Pipeline();

            string userfirstname = App.FirstName;
            var selectedImage = _mediaFile.GetStream();
            var selectedImage2 = _mediaFile2.GetStream();
            var selectedImage3 = _mediaFile3.GetStream();
            var selectedimage4 = _mediaFile4.GetStream();
            var page = new LoadingPage();


            BinaryReader br = new BinaryReader(stream);
            byte[] bytes = br.ReadBytes((Int32)stream.Length);



            await stream.ReadAsync(bytes, 0, (int)stream.Length);

            try
            {
                await PopupNavigation.Instance.PushAsync(page);

                SqlCommand sqlInsert = new SqlCommand("INSERT INTO t_Post(Post_Content, Photo, Photo_2, Photo_3, Photo_4, Uploader, Date_Uploaded) " +
                    "VALUES(@PostContent, @Photo, @Photo2, @Photo3, @Photo4, @Uploader, @DateUploaded)", databaseConnect.connectDB());

                sqlInsert.Parameters.AddWithValue("@PostContent", postContent.Text);
                sqlInsert.Parameters.AddWithValue("@Photo", selectedImage);
                sqlInsert.Parameters.AddWithValue("@Photo2", selectedImage2);
                sqlInsert.Parameters.AddWithValue("@Photo3", selectedImage3);
                sqlInsert.Parameters.AddWithValue("@Photo4", selectedimage4);
                sqlInsert.Parameters.AddWithValue("@Uploader", userfirstname);
                sqlInsert.Parameters.AddWithValue("@DateUploaded", DateTime.Now);

                int i = sqlInsert.ExecuteNonQuery();
                databaseConnect.connectDB().Close();

                if (_mediaFile != null || _mediaFile2 !=null || _mediaFile3 != null || _mediaFile4 != null)
                {
                    await DisplayAlert("Success", "Uploaded to Database.", "OK");
                    await PopupNavigation.Instance.PopAsync();
                    await Navigation.PopAsync();
                }

            }
            catch
            {

            }

        }

    }

for me it successfully writes to database using this code but it does not render all the images from the records
and gives me this error System.InvalidCastException: Specified cast is not valid when I tried to call the Photo_2 etc etc