ListRelatedFeatures.xaml.cs

// 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.Mapping;
using Esri.ArcGISRuntime.Maui;
using Esri.ArcGISRuntime.Portal;
using Colors = System.Drawing.Color;

namespace ArcGIS.Samples.ListRelatedFeatures
{
    [ArcGIS.Samples.Shared.Attributes.Sample(
        name: "List related features",
        category: "Data",
        description: "List features related to the selected feature.",
        instructions: "Tap on a feature to select it. The related features will be displayed in a list.",
        tags: new[] { "features", "identify", "query", "related", "relationship", "search" })]
    public partial class ListRelatedFeatures : ContentPage
    {
        // URL to the web map
        private readonly Uri _mapUri =
            new Uri("https://arcgisruntime.maps.arcgis.com/home/item.html?id=dcc7466a91294c0ab8f7a094430ab437");

        // Reference to the feature layer
        private FeatureLayer _myFeatureLayer;

        public ListRelatedFeatures()
        {
            InitializeComponent();

            // Create the UI, setup the control references and execute initialization
            _ = Initialize();
        }

        private async Task Initialize()
        {
            try
            {
                // Create the portal item from the URL to the webmap
                PortalItem alaskaPortalItem = await PortalItem.CreateAsync(_mapUri);

                // Create the map from the portal item
                Map myMap = new Map(alaskaPortalItem);

                // Add the map to the mapview
                MyMapView.Map = myMap;

                // Wait for the map to load
                await myMap.LoadAsync();

                // Get the feature layer from the map
                _myFeatureLayer = (FeatureLayer)myMap.OperationalLayers.First();

                // Make the selection color yellow.
                MyMapView.SelectionProperties.Color = Colors.Yellow;

                // Listen for GeoViewTapped events
                MyMapView.GeoViewTapped += MyMapViewOnGeoViewTapped;
            }
            catch (Exception e)
            {
                await Application.Current.MainPage.DisplayAlert("Error", e.ToString(), "OK");
            }
        }

        private async void MyMapViewOnGeoViewTapped(object sender, GeoViewInputEventArgs e)
        {
            try
            {
                // Clear any existing feature selection and results list
                _myFeatureLayer.ClearSelection();
                MyResultsView.ItemsSource = null;

                // Identify the tapped feature
                IdentifyLayerResult results = await MyMapView.IdentifyLayerAsync(_myFeatureLayer, e.Position, 10, false);

                // Return if there are no results
                if (results.GeoElements.Count < 1) { return; }

                Status.Text = "Loading...";

                // Get the first result
                ArcGISFeature myFeature = (ArcGISFeature)results.GeoElements.First();

                // Select the feature
                _myFeatureLayer.SelectFeature(myFeature);

                // Get the feature table for the feature
                ArcGISFeatureTable myFeatureTable = (ArcGISFeatureTable)myFeature.FeatureTable;

                // Query related features
                IReadOnlyList<RelatedFeatureQueryResult> relatedFeaturesResult = await myFeatureTable.QueryRelatedFeaturesAsync(myFeature);

                // Create a list to hold the formatted results of the query
                List<String> queryResultsForUi = new List<string>();

                // For each query result
                foreach (RelatedFeatureQueryResult result in relatedFeaturesResult)
                {
                    // And then for each feature in the result
                    foreach (Feature resultFeature in result)
                    {
                        // Get a reference to the feature's table
                        ArcGISFeatureTable relatedTable = (ArcGISFeatureTable)resultFeature.FeatureTable;

                        // Get the display field name - this is the name of the field that is intended for display
                        string displayFieldName = relatedTable.LayerInfo.DisplayFieldName;

                        // Get the name of the feature's table
                        string tableName = relatedTable.TableName;

                        // Get the display name for the feature
                        string featureDisplayname = resultFeature.Attributes[displayFieldName].ToString();

                        // Create a formatted result string
                        string formattedResult = $"{tableName} - {featureDisplayname}";

                        // Add the result to the list
                        queryResultsForUi.Add(formattedResult);
                    }
                }

                // Update the UI with the result list
                MyResultsView.ItemsSource = queryResultsForUi;
                Status.Text = "Tap a park (green) to see related features.";
            }
            catch (Exception ex)
            {
                await Application.Current.MainPage.DisplayAlert("Error", ex.ToString(), "OK");
            }
        }
    }
}