how to allow to upload less than 4 photo

Hi xamarin forum

I have created uploading 4 photo to server however if I try to upload like 2 photos the app crashes anyway here is the code for uploading

Upload.cs

        public partial class PostCreationPage : ContentPage
        {
            public List<t_Post> postslist;
            string json;

            public PostCreationPage()
            {
                InitializeComponent();

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

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

         private async void Upload_File(object sender, EventArgs e)
            {
                var content = new MultipartFormDataContent();
                var content2 = new MultipartFormDataContent();
                var content3 = new MultipartFormDataContent();
                var content4 = new MultipartFormDataContent();

                string userfirstname = App.FirstName;

                var page = new LoadingPage();




                content.Add(new StreamContent(_mediaFile.GetStream()),
                    "\"file\"",
                    $"\"{_mediaFile.Path}\"");

                content2.Add(new StreamContent(_mediaFile2.GetStream()),
                        "\"file\"",
                        $"\"{_mediaFile2.Path}\"");

                content3.Add(new StreamContent(_mediaFile3.GetStream()),
                        "\"file\"",
                        $"\"{_mediaFile3.Path}\"");

                content4.Add(new StreamContent(_mediaFile4.GetStream()),
                        "\"file\"",
                        $"\"{_mediaFile4.Path}\"");



                await PopupNavigation.Instance.PushAsync(page);

                var httpClient = new HttpClient();
                var uploadServiceBaseAddress = "http://xxx.xx.xx.xxx:8087/api/Files/Uploads";

                var httpResponseMessage = await httpClient.PostAsync(uploadServiceBaseAddress, content);
                var httpResponseMessage2 = await httpClient.PostAsync(uploadServiceBaseAddress, content2);


                var Absolutepath_1 = "http://xxx.xx.xx.xxx:8087/Uploads";
                var Absolutepath_2 = "http://xxx.xx.xx.xxx:8087/Uploads";
                var Absolutepath_3 = "http://xxx.xx.xx.xxx:8087/Uploads";
                var Absolutepath_4 = "http://xxx.xx.xx.xxx:8087/Uploads";

                var pathToLabel = httpResponseMessage.Content.ReadAsStringAsync().ToString();
                var pathToLabel2 = httpResponseMessage2.Content.ReadAsStringAsync().ToString();

                string pathName = Path.GetFileName(_mediaFile.Path);
                string pathName2 = Path.GetFileName(_mediaFile2.Path);
                string pathName3 = Path.GetFileName(_mediaFile3.Path);
                string pathName4 = Path.GetFileName(_mediaFile4.Path);

                string pathNames = Absolutepath_1 + "/" + pathName;
                string pathNames2 = Absolutepath_2 + "/" + pathName2;
                string pathNames3 = Absolutepath_3 + "/" + pathName3;
                string pathNames4 = Absolutepath_4 + "/" + pathName4;

                Pipeline databaseConnect = new Pipeline();

                try
                {

                    SqlCommand sqlInsert = new SqlCommand("INSERT INTO tablename(House_Name, Post_Content, Photo, Photo_2, Photo_3, Photo_4, Location, Floor_Area, Price, Bedroom, Toilet_And_Bath, Storey, Uploader, Date_Uploaded) " +
                    "VALUES(@HouseName, @PostContent, @Photo, @Photo2, @Photo3, @Photo4, @Location, @Price, @Floor, @Bedroom, @TB, @Storey, @Uploader, @DateUploaded)", databaseConnect.connectDB());

                    sqlInsert.Parameters.AddWithValue("@HouseName", HouseName.Text);
                    sqlInsert.Parameters.AddWithValue("@PostContent", postContent.Text);
                    sqlInsert.Parameters.AddWithValue("@Photo", pathNames);
                    sqlInsert.Parameters.AddWithValue("@Photo2", pathNames2);
                    sqlInsert.Parameters.AddWithValue("@Photo3", pathNames3);
                    sqlInsert.Parameters.AddWithValue("@Photo4", pathNames4);
                    sqlInsert.Parameters.AddWithValue("@Uploader", userfirstname);
                    sqlInsert.Parameters.AddWithValue("@DateUploaded", DateTime.Now);
                    sqlInsert.Parameters.AddWithValue("@Location", HouseLocation.Text);
                    sqlInsert.Parameters.AddWithValue("@Price", HousePrice.Text);
                    sqlInsert.Parameters.AddWithValue("@Floor", FloorArea.Text);
                    sqlInsert.Parameters.AddWithValue("@Bedroom", Bedroom.Text);
                    sqlInsert.Parameters.AddWithValue("@TB", BathToilet.Text);
                    sqlInsert.Parameters.AddWithValue("@Storey", Storey.Text);

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

                    await DisplayAlert("Success", "Uploaded to Database.", "OK");
                    await PopupNavigation.Instance.PopAsync();



                    await Navigation.PopAsync();
                }
                catch (Exception ex)
                {

                }

            }

        }
    }

Thanks in advance