Howto upload an image from Android mobile to an WEB API,tried the solution discussed here in vain

Tried : https://forums.xamarin.com/discussion/18649/best-practice-to-upload-image-selected-to-a-web-api?
My code :
private async void upload()
{
var file = mimgname; // "path/to/file.ext";
var url = NetworkCheck.ipAddr() + "/lcappi/imgupload/imgupload.php";
try
{

             System.IO.Stream fileStream = System.IO.File.Open(file, FileMode.Open);
              byte[] data = ReadFully(fileStream);
            fileStream.Close();
             MultipartFormDataContent multi = new MultipartFormDataContent();
            ByteArrayContent imageStream = new ByteArrayContent(data);
            StringContent SequenceID = new StringContent(osequence);
            imageStream.Headers.ContentType = new MediaTypeHeaderValue("image/jpg");
            imageStream.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
            {
                FileName = osequence, // "screenshot.jpg",   // generate this and send 
                Name = "avatar",
            };

             multi.Add(imageStream);
             alertLabel.Text = "Uploading Now";
            var response =
                    await App.client.PostAsync(url, multi);

            string responsestr = response.Content.ReadAsStringAsync().Result;

            var retresponse = new retResponse();
            bool uploadSuccess = false;
            if (responsestr != "")
            {
                retresponse = JsonConvert.DeserializeObject<retResponse>(responsestr);
                if (retresponse.status2 == 1) uploadSuccess = true;
            }

            if (uploadSuccess)
            {
                alertLabel.Text = "Image uploaded successfully";
                DependencyService.Get<IFileManager>().DeleteFile(file);// (file.Path);
                Application.Current.MainPage.Navigation.PopAsync(); //Remove the page currently on top.
            }

            alertLabel.Text = "After Upload Command2 ";
            if (responsestr != "") alertLabel.Text = responsestr.ToString(); else alertLabel.Text = alertLabel.Text + " After Upload Command ";

        }
        catch (Exception e)
        {

        }

    } // private void upload(MediaFile mediaFile)

I am able to upload smaller images (< 570kb) . Larger ones are not getting uploaded. I checked the web api using Postman where I could upload files as large as 2 mb. So I don't this the Res APi is the issue.

I am using CrossMedia to Capture image from camera. Then I am navigating to another page to display the captured image and let user click a button to upload. The code for this as follows:

private async void ImageButton_Clicked(object sender, EventArgs e)
{

            alertLabel.Text = "state1";
            if (!CrossMedia.Current.IsCameraAvailable || !CrossMedia.Current.IsTakePhotoSupported)
            {
                alertLabel.Text = "state1 if start";
                //// DisplayAlert("No Camera", ":( No camera available.", "OK");
                alertLabel.Text = "state1 if end ";
                return;

            }
              var mediaOptions = new Plugin.Media.Abstractions.StoreCameraMediaOptions
            {
                Directory = "LCAPP",
                //// Name = $"{DateTime.UtcNow}.jpg",
                Name = $"Tempimg.jpg",
                SaveToAlbum = true,
                CompressionQuality = 100,
                CustomPhotoSize = 50,
                PhotoSize = PhotoSize.MaxWidthHeight,
                MaxWidthHeight = 2000,
                DefaultCamera = Plugin.Media.Abstractions.CameraDevice.Rear
            };
            alertLabel.Text = "state1 after var mediaOptions ";

            var file = await CrossMedia.Current.TakePhotoAsync(mediaOptions);
            alertLabel.Text = "state1 after var file ";
            if (file == null)
                return;
            var filePath = file.Path;
            // filePath = "LCAPP/*.*";
            var directory = file.AlbumPath;
            // DisplayAlert("File Location", file.Path, "OK");
            alertLabel.Text = "state1 before var image source  ";
        alertLabel.Text = file.AlbumPath;

         file.Dispose();


                  var imageparam = new ImageParams
        {
            imgName = filePath.ToString(),
            locID = 20

        };

        var imagepage = new ShowImage(imageparam.imgName,opdetailSequenceForImage);
                  App.imgDelete = false;
        await Navigation.PushAsync(imagepage);
     }

Donot know how to resolve this, breaking my head