Service feature table (no cache)

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Display a feature layer from a service using the no cache feature request mode.

Image of service feature table no cache

Use case

ServiceFeatureTable supports three request modes, which define how features are requested from the service and stored in the local table. The feature request modes have different performance characteristics. Use no cache in scenarios where you always want the freshest data.

How to use the sample

Run the sample and pan and zoom around the map. With each interaction, new features will be requested from the service and displayed on the map.

How it works

  1. Set the ServiceFeatureTable.FeatureRequestMode property of the service feature table to NO_CACHE before the table is loaded.
  2. Add the table to the map using a FeatureLayer; features will be requested for the visible extent as the user pans and zooms.

Relevant API

  • FeatureLayer
  • FeatureRequestMode.NoCache
  • ServiceFeatureTable
  • ServiceFeatureTable.PopulateFromServiceAsync
  • ServiceFeatureTable.FeatureRequestMode

About the data

The sample uses a feature service showing pool permits for land parcels in a Riverside, CA neighborhood.

Additional information

In no cache mode, features are automatically populated from the service for the visible extent. Each time the user pans and zooms, features are downloaded for the visible extent. Features are still cached in a local geodatabase for display, but the cache will always be populated with the latest data after navigation.

NOTE: No cache does not guarantee that features won't be cached locally; feature request mode is a performance concept unrelated to data security.

Tags

cache, feature request mode, performance

Sample Code

ServiceFeatureTableNoCache.cs
                                                                                                
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// Copyright 2016 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 System;
using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using UIKit;

namespace ArcGISRuntime.Samples.ServiceFeatureTableNoCache
{
    [Register("ServiceFeatureTableNoCache")]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Service feature table (no cache)",
        category: "Data",
        description: "Display a feature layer from a service using the **no cache** feature request mode.",
        instructions: "Run the sample and pan and zoom around the map. With each interaction, new features will be requested from the service and displayed on the map.",
        tags: new[] { "cache", "feature request mode", "performance" })]
    public class ServiceFeatureTableNoCache : UIViewController
    {
        // Hold references to UI controls.
        private MapView _myMapView;

        public ServiceFeatureTableNoCache()
        {
            Title = "Service feature table (no cache)";
        }

        private void Initialize()
        {
            // Create new Map with basemap.
            Map myMap = new Map(BasemapStyle.ArcGISTopographic);

            // Create and set initial map area.
            Envelope initialLocation = new Envelope(-1.30758164047166E7, 4014771.46954516, -1.30730056797177E7, 4016869.78617381, SpatialReferences.WebMercator);
            myMap.InitialViewpoint = new Viewpoint(initialLocation);

            // Create URI to the feature service.
            Uri serviceUri = new Uri("https://sampleserver6.arcgisonline.com/arcgis/rest/services/PoolPermits/FeatureServer/0");

            // Create feature table for the pools feature service.
            ServiceFeatureTable poolsFeatureTable = new ServiceFeatureTable(serviceUri)
            {
                // Define the request mode.
                FeatureRequestMode = FeatureRequestMode.OnInteractionNoCache
            };

            // Create FeatureLayer that uses the created table.
            FeatureLayer poolsFeatureLayer = new FeatureLayer(poolsFeatureTable);

            // Add created layer to the map.
            myMap.OperationalLayers.Add(poolsFeatureLayer);

            // Assign the map to the MapView.
            _myMapView.Map = myMap;

            // Feature table initialization.
            poolsFeatureTable.RetryLoadAsync();
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();
            Initialize();
        }

        public override void LoadView()
        {
            // Create the views.
            _myMapView = new MapView();
            _myMapView.TranslatesAutoresizingMaskIntoConstraints = false;

            View = new UIView() { BackgroundColor = ApplicationTheme.BackgroundColor };

            // Add the views.
            View.AddSubviews(_myMapView);

            // Lay out the views.
            NSLayoutConstraint.ActivateConstraints(new[]
            {
                _myMapView.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _myMapView.BottomAnchor.ConstraintEqualTo(View.BottomAnchor),
                _myMapView.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _myMapView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor)
            });
        }
    }
}

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