Add, delete, and download attachments for features from a service.
Use case
Attachments provide a flexible way to manage additional information that is related to your features. Attachments allow you to add files to individual features, including: PDFs, text documents, or any other type of file. For example, if you have a feature representing a building, you could use attachments to add multiple photographs of the building taken from several angles, along with PDF files containing the building's deed and tax information.
How to use the sample
Tap a feature to load its attachments. Use the buttons to save, delete, or add attachments.
How it works
- Create a
ServiceFeatureTablefrom a URL. - Create a
FeatureLayerobject from the service feature table. - Select features from the feature layer with
FeatureLayer.SelectFeatures(). - To fetch the feature's attachments, cast to an
ArcGISFeatureand useArcGISFeature.GetAttachmentsAsync(). - To add an attachment to the selected ArcGISFeature, create an attachment and use
ArcGISFeature.AddAttachmentAsync(). - To delete an attachment from the selected ArcGISFeature, use the
ArcGISFeature.DeleteAttachmentAsync(). - After a change, apply the changes to the server using
ServiceFeatureTable.ApplyEditsAsync().
Relevant API
- ApplyEditsAsync
- DeleteAttachmentAsync
- FeatureLayer
- FetchAttachmentsAsync
- FetchDataAsync
- ServiceFeatureTable
- UpdateFeatureAsync
Additional information
Attachments can only be added to and accessed on service feature tables when their HasAttachments property is true.
Tags
data, image, JPEG, PDF, picture, PNG, TXT
Sample Code
// Copyright 2022 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
// You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific
// language governing permissions and limitations under the License.
using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
// Custom code is needed for presenting the image picker on iOS.
#if IOS || MACCATALYST
using Foundation;
using UIKit;
#endif
namespace ArcGIS.Samples.EditFeatureAttachments
{
[ArcGIS.Samples.Shared.Attributes.Sample(
name: "Edit feature attachments",
category: "Data",
description: "Add, delete, and download attachments for features from a service.",
instructions: "Tap a feature to load its attachments. Use the buttons to save, delete, or add attachments.",
tags: new[] { "JPEG", "PDF", "PNG", "TXT", "data", "image", "picture" })]
public partial class EditFeatureAttachments : ContentPage
{
// URL to the feature service.
private const string FeatureServiceUrl = "https://sampleserver6.arcgisonline.com/arcgis/rest/services/DamageAssessment/FeatureServer/0";
// Hold a reference to the feature layer.
private FeatureLayer _damageLayer;
// Hold a reference to the recently selected feature.
private ArcGISFeature _selectedFeature;
public EditFeatureAttachments()
{
InitializeComponent();
_ = Initialize();
}
private async Task Initialize()
{
try
{
// Create the map with streets basemap.
MyMapView.Map = new Map(BasemapStyle.ArcGISStreets);
// Create the feature table, referring to the Damage Assessment feature service.
ServiceFeatureTable damageTable = new ServiceFeatureTable(new Uri(FeatureServiceUrl));
// Create a feature layer to visualize the features in the table.
_damageLayer = new FeatureLayer(damageTable);
// Add the layer to the map.
MyMapView.Map.OperationalLayers.Add(_damageLayer);
// Listen for user taps on the map.
MyMapView.GeoViewTapped += MapView_Tapped;
// Zoom to the United States.
_ = MyMapView.SetViewpointCenterAsync(new MapPoint(-10800000, 4500000, SpatialReferences.WebMercator), 3e7);
}
catch (Exception ex)
{
await Application.Current.MainPage.DisplayAlert("Error", ex.ToString(), "OK");
}
}
private async void MapView_Tapped(object sender, Esri.ArcGISRuntime.Maui.GeoViewInputEventArgs e)
{
// Clear any existing selection.
_damageLayer.ClearSelection();
_selectedFeature = null;
// Reset the UI.
AttachmentsListBox.IsEnabled = false;
AttachmentsListBox.ItemsSource = null;
AddAttachmentButton.IsEnabled = false;
try
{
// Perform an identify to determine if a user tapped on a feature.
IdentifyLayerResult identifyResult = await MyMapView.IdentifyLayerAsync(_damageLayer, e.Position, 2, false);
// Do nothing if there are no results.
if (!identifyResult.GeoElements.Any())
{
return;
}
// Get the selected feature as an ArcGISFeature. It is assumed that all GeoElements in the result are of type ArcGISFeature.
GeoElement tappedElement = identifyResult.GeoElements.First();
ArcGISFeature tappedFeature = (ArcGISFeature)tappedElement;
// Select the feature in the UI and hold a reference to the tapped feature in a field.
_damageLayer.SelectFeature(tappedFeature);
_selectedFeature = tappedFeature;
// Load the feature.
await tappedFeature.LoadAsync();
// Populate the UI with a list of attachments that have a content type of image/jpeg.
AttachmentsListBox.ItemsSource = await GetJpegAttachmentsAsync(tappedFeature);
AttachmentsListBox.IsEnabled = true;
AddAttachmentButton.IsEnabled = true;
}
catch (Exception ex)
{
await Application.Current.MainPage.DisplayAlert("Error selecting feature", ex.ToString(), "OK");
}
}
private async void AddAttachment_Click(object sender, EventArgs e)
{
if (_selectedFeature == null)
{
return;
}
// Adjust the UI.
AddAttachmentButton.IsEnabled = false;
AttachmentActivityIndicator.IsVisible = true;
// Get the file.
string contentType = "image/jpeg";
try
{
byte[] attachmentData;
string filename;
// Microsoft.Maui.Storage.FilePicker shows the iCloud picker (not photo picker) on iOS.
#if IOS || MACCATALYST
attachmentData = await GetImageBytesAsync();
// Return if no image was loaded.
if (attachmentData == null) return;
if (!_filename.EndsWith(".jpg") && !_filename.EndsWith(".jpeg"))
{
await Application.Current.MainPage.DisplayAlert("Try again!", "This sample only allows uploading jpg files.", "OK");
return;
}
filename = _filename;
#else
// Show a file picker
FileResult fileData = await FilePicker.PickAsync(new PickOptions { FileTypes = FilePickerFileType.Jpeg });
if (fileData == null)
{
return;
}
if (!fileData.FileName.EndsWith(".jpg") && !fileData.FileName.EndsWith(".jpeg"))
{
await Application.Current.MainPage.DisplayAlert("Try again!", "This sample only allows uploading jpg files.", "OK");
return;
}
using (Stream fileStream = await fileData.OpenReadAsync())
{
using (var memoryStream = new MemoryStream())
{
await fileStream.CopyToAsync(memoryStream);
attachmentData = memoryStream.ToArray();
}
}
filename = fileData.FileName;
#endif
// Add the attachment.
// The contentType string is the MIME type for JPEG files, image/jpeg.
await _selectedFeature.AddAttachmentAsync(filename, contentType, attachmentData);
// Get a reference to the feature's service feature table.
ServiceFeatureTable serviceTable = (ServiceFeatureTable)_selectedFeature.FeatureTable;
// Apply the edits to the service feature table.
await serviceTable.ApplyEditsAsync();
// Update UI.
_selectedFeature.Refresh();
AttachmentsListBox.ItemsSource = await GetJpegAttachmentsAsync(_selectedFeature);
await Application.Current.MainPage.DisplayAlert("Success!", "Successfully added attachment", "OK");
}
catch (Exception exception)
{
await Application.Current.MainPage.DisplayAlert("Error adding attachment", exception.Message, "OK");
}
finally
{
// Adjust the UI.
AddAttachmentButton.IsEnabled = true;
AttachmentActivityIndicator.IsVisible = false;
}
}
private async void DeleteAttachment_Click(object sender, EventArgs e)
{
AttachmentActivityIndicator.IsVisible = true;
try
{
// Get the attachment that should be deleted.
Button sendingButton = (Button)sender;
Attachment selectedAttachment = (Attachment)sendingButton.BindingContext;
// Delete the attachment.
await _selectedFeature.DeleteAttachmentAsync(selectedAttachment);
// Get a reference to the feature's service feature table.
ServiceFeatureTable serviceTable = (ServiceFeatureTable)_selectedFeature.FeatureTable;
// Apply the edits to the service feature table.
await serviceTable.ApplyEditsAsync();
// Update UI.
_selectedFeature.Refresh();
AttachmentsListBox.ItemsSource = await GetJpegAttachmentsAsync(_selectedFeature);
// Show success message.
await Application.Current.MainPage.DisplayAlert("Success!", "Successfully deleted attachment", "OK");
}
catch (Exception exception)
{
await Application.Current.MainPage.DisplayAlert("Error deleting attachment", exception.ToString(), "OK");
}
finally
{
AttachmentActivityIndicator.IsVisible = false;
}
}
private async void DownloadAttachment_Click(object sender, EventArgs e)
{
try
{
// Get a reference to the button that raised the event.
Button sendingButton = (Button)sender;
// Get the attachment from the button's DataContext. The button's DataContext is set by the list view.
Attachment selectedAttachment = (Attachment)sendingButton.BindingContext;
if (selectedAttachment.ContentType.Contains("image"))
{
// Create a preview and show it.
ContentPage previewPage = new ContentPage();
previewPage.Title = "Attachment preview";
Image imageView = new Image();
Stream contentStream = await selectedAttachment.GetDataAsync();
imageView.Source = ImageSource.FromStream(() => contentStream);
previewPage.Content = imageView;
await Application.Current.MainPage.Navigation.PushAsync(previewPage);
}
else
{
await Application.Current.MainPage.DisplayAlert("Can't show attachment", "This sample can only show image attachments.", "OK");
}
}
catch (Exception exception)
{
await Application.Current.MainPage.DisplayAlert("Error reading attachment", exception.ToString(), "OK");
}
}
private static async Task<IEnumerable<Attachment>> GetJpegAttachmentsAsync(ArcGISFeature feature)
{
IReadOnlyList<Attachment> attachments = await feature.GetAttachmentsAsync();
return attachments.Where(attachment => attachment.ContentType == "image/jpeg").ToList();
}
// Image picker implementation for iOS using UIImagePickerController.
// Microsoft.Maui.Storage.FilePicker shows an iCloud file picker; comment this out
// and use the cross-platform implementation if that's what you want.
#if IOS
private TaskCompletionSource<byte[]> _taskCompletionSource;
private UIImagePickerController _imagePicker;
private string _filename;
private Task<byte[]> GetImageBytesAsync()
{
// Create and define UIImagePickerController.
_imagePicker = new UIImagePickerController
{
SourceType = UIImagePickerControllerSourceType.PhotoLibrary,
MediaTypes = UIImagePickerController.AvailableMediaTypes(UIImagePickerControllerSourceType.PhotoLibrary)
};
// Set event handlers.
_imagePicker.FinishedPickingMedia += OnImagePickerFinishedPickingMedia;
_imagePicker.Canceled += OnImagePickerCancelled;
// Present UIImagePickerController.
UIWindow window = UIApplication.SharedApplication.KeyWindow;
var viewController = window.RootViewController;
viewController.PresentViewController(_imagePicker, true, null);
// Return Task object.
_taskCompletionSource = new TaskCompletionSource<byte[]>();
return _taskCompletionSource.Task;
}
private void OnImagePickerFinishedPickingMedia(object sender, UIImagePickerMediaPickedEventArgs args)
{
// The picker can have values for an edited image and an original image. We use the edited image if it is not null.
UIImage image = args.EditedImage ?? args.OriginalImage;
// Set the filename for later use.
_filename = args.ImageUrl.LastPathComponent;
if (image != null)
{
// Get the image data.
NSData data = image.AsJPEG(1);
// Set the byte array as the completion of the Task.
_taskCompletionSource.SetResult(data.ToArray());
}
else
{
_taskCompletionSource.SetResult(null);
}
UnregisterEventHandlers();
}
private void OnImagePickerCancelled(object sender, EventArgs args)
{
UnregisterEventHandlers();
_taskCompletionSource.SetResult(null);
}
private void UnregisterEventHandlers()
{
_imagePicker.FinishedPickingMedia -= OnImagePickerFinishedPickingMedia;
_imagePicker.Canceled -= OnImagePickerCancelled;
_imagePicker.DismissViewController(true, null);
}
#endif
// Image picker implementation for Mac using UIDocumentPickerViewController.
#if MACCATALYST
private TaskCompletionSource<byte[]> _taskCompletionSource;
private UIDocumentPickerViewController _imagePicker;
private string _filename;
public async Task<byte[]> GetImageBytesAsync()
{
var allowedTypes = new UniformTypeIdentifiers.UTType[]
{
UniformTypeIdentifiers.UTTypes.Image,
};
_imagePicker = new UIDocumentPickerViewController(allowedTypes) { AllowsMultipleSelection = false };
_taskCompletionSource = new TaskCompletionSource<byte[]>();
_imagePicker.DidPickDocument += DocumentPicked;
_imagePicker.DidPickDocumentAtUrls += DocumentAtUrlsPicked;
_imagePicker.WasCancelled += DocumentCancelled;
// Present the UIDocumentPickerViewController.
UIWindow window = UIApplication.SharedApplication.KeyWindow;
var viewController = window.RootViewController;
viewController.PresentViewController(_imagePicker, true, null);
return await _taskCompletionSource.Task;
}
private void DocumentPicked(object sender, UIDocumentPickedEventArgs e)
{
PickDocumentAsync(e.Url);
}
private void DocumentAtUrlsPicked(object sender, UIDocumentPickedAtUrlsEventArgs e)
{
PickDocumentAsync(e.Urls[0]);
}
private void DocumentCancelled(object sender, EventArgs e)
{
// A null result will cancel without presenting an error message.
_taskCompletionSource.TrySetResult(null);
UnregisterEventHandlers();
}
private void PickDocumentAsync(NSUrl url)
{
try
{
// Set the filename for later use.
_filename = url.LastPathComponent;
// Load the data from the local file.
NSData data = NSData.FromUrl(url);
// Set the byte array as the completion of the Task.
_taskCompletionSource.TrySetResult(data.ToArray());
}
catch (Exception ex)
{
System.Diagnostics.Debug.Print(ex.Message);
_taskCompletionSource.TrySetException(ex);
}
finally
{
UnregisterEventHandlers();
}
}
private void UnregisterEventHandlers()
{
_imagePicker.DidPickDocument -= DocumentPicked;
_imagePicker.DidPickDocumentAtUrls -= DocumentAtUrlsPicked;
_imagePicker.WasCancelled -= DocumentCancelled;
_imagePicker.DismissViewController(true, null);
}
#endif
}
}