ArcGIS Runtime SDK for .NET Samples

Query map image layer tables

Find related features for a selected row in a table
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// 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 System;
using System.Collections.Generic;
using System.Linq;
using Esri.ArcGISRuntime.ArcGISServices;
using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Symbology;
using Esri.ArcGISRuntime.UI;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using UIKit;

namespace ArcGISRuntime.Samples.MapImageLayerTables
{
    [Register("MapImageLayerTables")]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        "Query map image layer tables",
        "Layers",
        "This sample demonstrates how to get a non-spatial table from an ArcGIS map image layer. It shows how to query such a table, as well as how to find related features in another table. The non-spatial tables contained by a map service may contain additional information about sublayer features. Such information can be accessed by traversing table relationships defined in the service.",
        "1. Launch the sample, the map displays at the extent of the `Service Requests` layer.\n2. The list is populated with service request comment records that have a valid(non-null) comment.\n3. Select one of the service request comments from the list to see the related service request feature selected in the map.",
        "Query", "Sublayer", "MapServer", "Related Tables")]
    public class MapImageLayerTables : UIViewController
    {
        // MapView control for displaying the map.
        private MapView _myMapView;

        // A graphics overlay for showing selected features.
        private GraphicsOverlay _selectedFeaturesOverlay;

        // A table view to show comment records.
        private UITableView _tableView;

        // A list of all service request comment records (non-spatial features).
        private List<ArcGISFeature> _serviceRequestComments = new List<ArcGISFeature>();

        public MapImageLayerTables()
        {
            Title = "Query map image layer tables";
        }

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

            // Create the UI and initialize the map and table view.
            CreateLayout();
            Initialize();
        }

        private async void Initialize()
        {
            // Create a new Map with a vector streets basemap.
            Map myMap = new Map(Basemap.CreateStreetsVector());

            // Create the URI to the Service Requests map service.
            Uri serviceRequestUri = new Uri("https://sampleserver6.arcgisonline.com/arcgis/rest/services/ServiceRequest/MapServer");

            // Create a new ArcGISMapImageLayer that uses the service URI.
            ArcGISMapImageLayer serviceRequestsMapImageLayer = new ArcGISMapImageLayer(serviceRequestUri);

            // Load all sublayers and tables contained by the map image layer.
            await serviceRequestsMapImageLayer.LoadTablesAndLayersAsync();

            // Set the initial map extent to the extent of all service request features.
            Envelope requestsExtent = serviceRequestsMapImageLayer.FullExtent;
            myMap.InitialViewpoint = new Viewpoint(requestsExtent);

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

            // Get the service request comments table from the map image layer.
            ServiceFeatureTable commentsTable = serviceRequestsMapImageLayer.Tables[0];

            // Create query parameters to get all non-null service request comment records (features) from the table.
            QueryParameters queryToGetNonNullComments = new QueryParameters
            {
                WhereClause = "requestid <> '' AND comments <> ''"
            };

            // Query the comments table to get the non-null records.
            FeatureQueryResult commentQueryResult = await commentsTable.QueryFeaturesAsync(queryToGetNonNullComments, QueryFeatureFields.LoadAll);

            // Show the records from the service request comments table in the UITableView control.
            foreach (ArcGISFeature commentFeature in commentQueryResult)
            {
                _serviceRequestComments.Add(commentFeature);
            }
            
            // Create the table view source that uses the list of features.
            ServiceRequestCommentsTableSource commentsTableSource = new ServiceRequestCommentsTableSource(_serviceRequestComments);

            // Handle a new selection in the table source.
            commentsTableSource.ServiceRequestCommentSelected += CommentsTableSource_ServiceRequestCommentSelected;

            // Assign the table view source to the table view control.
            _tableView.Source = commentsTableSource;

            // Create a graphics overlay to show selected features and add it to the map view.
            _selectedFeaturesOverlay = new GraphicsOverlay();
            _myMapView.GraphicsOverlays.Add(_selectedFeaturesOverlay);

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

            // Reload the table view data to refresh the display.
            _tableView.ReloadData();
        }

        // Handle a new selected comment record in the table view.
        private async void CommentsTableSource_ServiceRequestCommentSelected(object sender, ServiceRequestCommentSelectedEventArgs e)
        {
            // Clear selected features from the graphics overlay.
            _selectedFeaturesOverlay.Graphics.Clear();

            // Get the map image layer that contains the service request sublayer and the service request comments table.
            ArcGISMapImageLayer serviceRequestsMapImageLayer = _myMapView.Map.OperationalLayers[0] as ArcGISMapImageLayer;

            // Get the (non-spatial) table that contains the service request comments.
            ServiceFeatureTable commentsTable = serviceRequestsMapImageLayer.Tables[0];

            // Get the relationship that defines related service request features for features in the comments table (this is the first and only relationship).
            RelationshipInfo commentsRelationshipInfo = commentsTable.LayerInfo.RelationshipInfos.FirstOrDefault();

            // Create query parameters to get the related service request for features in the comments table.
            RelatedQueryParameters relatedQueryParams = new RelatedQueryParameters(commentsRelationshipInfo)
            {
                ReturnGeometry = true
            };

            // Query the comments table to get the related service request feature for the selected comment.
            IReadOnlyList<RelatedFeatureQueryResult> relatedRequestsResult = await commentsTable.QueryRelatedFeaturesAsync(e.SelectedComment, relatedQueryParams);

            // Get the first result. 
            RelatedFeatureQueryResult result = relatedRequestsResult.FirstOrDefault();

            // Get the first feature from the result. If it's null, warn the user and return.
            ArcGISFeature serviceRequestFeature = result.FirstOrDefault() as ArcGISFeature;
            if (serviceRequestFeature == null)
            {
                UIAlertController alert = UIAlertController.Create("No Feature", "Related feature not found.", UIAlertControllerStyle.Alert);
                alert.AddAction(UIAlertAction.Create("OK", UIAlertActionStyle.Default, null));
                PresentViewController(alert, true, null);

                return;
            }

            // Load the related service request feature (so its geometry is available).
            await serviceRequestFeature.LoadAsync();

            // Get the service request geometry (point).
            MapPoint serviceRequestPoint = serviceRequestFeature.Geometry as MapPoint;

            // Create a cyan marker symbol to display the related feature.
            Symbol selectedRequestSymbol = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle.Circle, System.Drawing.Color.Cyan, 14);

            // Create a graphic using the service request point and marker symbol.
            Graphic requestGraphic = new Graphic(serviceRequestPoint, selectedRequestSymbol);

            // Add the graphic to the graphics overlay and zoom the map view to its extent.
            _selectedFeaturesOverlay.Graphics.Add(requestGraphic);
            await _myMapView.SetViewpointCenterAsync(serviceRequestPoint, 150000);
        }

        private void CreateLayout()
        {
            // Create a UIStackView for laying out the map view and table view.
            var stackView = new UIStackView(new CoreGraphics.CGRect(0, 0, View.Bounds.Width, View.Bounds.Height))
            {
                Axis = UILayoutConstraintAxis.Vertical,
                Alignment = UIStackViewAlignment.Fill,
                Distribution = UIStackViewDistribution.FillProportionally,
                BackgroundColor = UIColor.Gray
            };

            // Create the map view and add it to the stack view.
            _myMapView = new MapView();
            stackView.AddArrangedSubview(_myMapView);

            // Create a table view for displaying records from the comments table.
            _tableView = new UITableView();

            // Add the table view to the stack view.
            stackView.AddArrangedSubview(_tableView);

            // Add the stack view to the page.
            View.AddSubviews(stackView);
        }
    }

    // A class to define a custom table view source for displaying the ID and description from service request comment features.
    internal class ServiceRequestCommentsTableSource : UITableViewSource
    {
        // An event that's fired when a new service request comment row is selected in the source.
        public event NewCommentSelectedHandler ServiceRequestCommentSelected;

        // A delegate to fire the ServiceRequestCommentSelected event and return the selected feature.
        public delegate void NewCommentSelectedHandler(object sender, ServiceRequestCommentSelectedEventArgs e);

        // A list of service request comment features.
        private readonly List<ArcGISFeature> _comments;

        // An identifier for the table cell (for cell reuse).
        private const string CellIdentifier = "TableCell";

        // Store the selected row.
        private ArcGISFeature _selectedCommentRecord;

        // The constructor takes a list of service request comment features.
        public ServiceRequestCommentsTableSource(List<ArcGISFeature> comments)
        {
            _comments = comments;
        }

        // Number of sections (groups) to display.
        public override nint NumberOfSections(UITableView tableView)
        {
            return 1;
        }

        // When the selected row changes, raise the ServiceRequestCommentSelected event to return the selected feature.
        public override void RowSelected(UITableView tableView, NSIndexPath indexPath)
        {
            _selectedCommentRecord = _comments[indexPath.Row];
            ServiceRequestCommentSelected?.Invoke(this, new ServiceRequestCommentSelectedEventArgs(_selectedCommentRecord));
        }

        // Number of rows in the specified section (group).
        public override nint RowsInSection(UITableView tableview, nint section)
        {
            // If the feature list is null, return 0. Otherwise the number of features in the internal comments list.
            return _comments != null ? _comments.Count : 0;
        }

        // Get the cell to display for the specified row.
        public override UITableViewCell GetCell(UITableView tableView, NSIndexPath indexPath)
        {
            // Get the reused cell from the table view.
            UITableViewCell cell = tableView.DequeueReusableCell(CellIdentifier);

            // Get the comment feature at this cell index.
            Feature commentRow = _comments[indexPath.Row];

            // If there wasn't a cell for reuse, create a new one.
            if (cell == null)
            {
                // Value1 provides a text label (for the request ID) and detail text label (for the comment text).
                cell = new UITableViewCell(UITableViewCellStyle.Value1, CellIdentifier);
            }

            // Fill the cell text with attributes from the comment feature.
            cell.DetailTextLabel.Text = commentRow.Attributes["comments"].ToString();

            // Return the populated cell for display.
            return cell;
        }
    }

    // A custom class to define the event arguments to return when a new row is selected.
    internal class ServiceRequestCommentSelectedEventArgs : EventArgs
    {
        // Store the selected service request comment feature.
        internal ArcGISFeature SelectedComment { get; set; }

        // Constructor takes the service request comment feature that was selected.
        public ServiceRequestCommentSelectedEventArgs(ArcGISFeature selectedComment)
        {
            SelectedComment = selectedComment;
        }
    }
}


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