List related features

<UserControl x:Class="ArcGIS.WinUI.Samples.ListRelatedFeatures.ListRelatedFeatures"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:esriUI="using:Esri.ArcGISRuntime.UI.Controls">
    <Grid>
        <esriUI:MapView x:Name="MyMapView" />
        <Border Style="{StaticResource BorderStyle}">
            <StackPanel>
                <TextBlock Margin="0,0,0,10"
                           FontWeight="SemiBold"
                           Text="Tap a park (green) to see related features."
                           TextAlignment="Center" />
                <ProgressBar x:Name="LoadingProgress"
                             Height="15"
                             Margin="0,0,0,10"
                             IsIndeterminate="True"
                             Visibility="Visible" />
                <ListView x:Name="MyResultsView"
                          MaxHeight="300"
                          ScrollViewer.HorizontalScrollBarVisibility="Disabled"
                          SelectionMode="None">
                    <ListView.ItemTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding}" TextWrapping="Wrap" />
                        </DataTemplate>
                    </ListView.ItemTemplate>
                </ListView>
            </StackPanel>
        </Border>
    </Grid>
</UserControl>

// Copyright 2018 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.Portal;
using Esri.ArcGISRuntime.UI.Controls;
using Microsoft.UI.Xaml;
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Threading.Tasks;

namespace ArcGIS.WinUI.Samples.ListRelatedFeatures
{
    [ArcGIS.Samples.Shared.Attributes.Sample(
        name: "List related features",
        category: "Data",
        description: "List features related to the selected feature.",
        instructions: "Click 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
    {
        // 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();

            // 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();

                // Wait for the layer to load.
                await _myFeatureLayer.LoadAsync();

                // Update the selection color.
                MyMapView.SelectionProperties.Color = Color.Yellow;

                // Listen for GeoViewTapped events.
                MyMapView.GeoViewTapped += MyMapViewOnGeoViewTapped;

                // Hide the loading indicator.
                LoadingProgress.Visibility = Visibility.Collapsed;
            }
            catch (Exception e)
            {
                await new MessageDialog2(e.ToString(), "Error").ShowAsync();
            }
        }

        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;
                }

                // Show the loading indicator (this can take a while).
                LoadingProgress.Visibility = Visibility.Visible;

                // 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;

                // Hide the loading indicator.
                LoadingProgress.Visibility = Visibility.Collapsed;
            }
            catch (Exception ex)
            {
                await new MessageDialog2(ex.ToString(), "Error").ShowAsync();
            }
        }
    }
}