ArcGIS Runtime SDK for .NET Samples

Query feature count and extent

Query feature count or get the extent of matching features
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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 Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using System;
using UIKit;

namespace ArcGISRuntime.Samples.QueryFeatureCountAndExtent
{
    [Register("QueryFeatureCountAndExtent")]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        "Query feature count and extent",
        "Analysis",
        "This sample demonstrates how to query a feature table, in this case returning a count, for features that are within the visible extent or that meet specified criteria.",
        "Use the button to zoom to the extent of the state specified (by abbreviation) in the textbox or use the button to count the features in the current extent.")]
    public class QueryFeatureCountAndExtent : UIViewController
    {
        // Create and hold reference to the used MapView
        private readonly MapView _myMapView = new MapView();

        // Button for querying cities in the current extent
        private UIButton _myQueryExtentButton;

        // Button for querying cities by state
        private UIButton _myQueryStateButton;

        // Search box for entering state name
        private UISearchBar _myStateEntry;

        // Label to show the results
        private UILabel _myResultsLabel;

        // URL to the feature service
        private readonly Uri _usaCitiesSource = new Uri("https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer/0");

        // Feature table to query
        private ServiceFeatureTable _myFeatureTable;

        public QueryFeatureCountAndExtent()
        {
            Title = "Query feature count and extent";
        }

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

            // Create the feature table from the service URL
            _myFeatureTable = new ServiceFeatureTable(_usaCitiesSource);

            // Create the feature layer from the table
            FeatureLayer myFeatureLayer = new FeatureLayer(_myFeatureTable);

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

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

            // Set the map initial extent to the extent of the feature layer
            myMap.InitialViewpoint = new Viewpoint(myFeatureLayer.FullExtent);

            // Add the map to the MapView
            _myMapView.Map = myMap;
        }

        private async void BtnZoomToFeatures_Click(object sender, EventArgs e)
        {
            // Create the query parameters
            QueryParameters queryStates = new QueryParameters { WhereClause = $"upper(ST) LIKE '%{_myStateEntry.Text.ToUpper()}%'" };

            // Get the extent from the query
            Envelope resultExtent = await _myFeatureTable.QueryExtentAsync(queryStates);

            // Return if there is no result (might happen if query is invalid)
            if (resultExtent?.SpatialReference == null)
            {
                return;
            }

            // Create a viewpoint from the extent
            Viewpoint resultViewpoint = new Viewpoint(resultExtent);

            // Zoom to the viewpoint
            await _myMapView.SetViewpointAsync(resultViewpoint);

            // Update the UI
            _myResultsLabel.Text = $"Zoomed to features in {_myStateEntry.Text}";
        }

        private async void BtnCountFeatures_Click(object sender, EventArgs e)
        {
            // Create the query parameters
            QueryParameters queryCityCount = new QueryParameters
            {
                // Get the current view extent and use that as a query parameters
                Geometry = _myMapView.GetCurrentViewpoint(ViewpointType.BoundingGeometry).TargetGeometry,
                // Specify the interpretation of the Geometry query parameters
                SpatialRelationship = SpatialRelationship.Intersects
            };

            // Get the count of matching features
            long count = await _myFeatureTable.QueryFeatureCountAsync(queryCityCount);

            // Update the UI
            _myResultsLabel.Text = $"{count} features in extent";
        }

        private void CreateLayout()
        {
            // Create the extent query button and subscribe to events
            _myQueryExtentButton = new UIButton();
            _myQueryExtentButton.SetTitle("Count in Extent", UIControlState.Normal);
            _myQueryExtentButton.SetTitleColor(UIColor.Blue, UIControlState.Normal);
            _myQueryExtentButton.TouchUpInside += BtnCountFeatures_Click;

            // Create the state query button and subscribe to events
            _myQueryStateButton = new UIButton();
            _myQueryStateButton.SetTitle("Zoom to match", UIControlState.Normal);
            _myQueryStateButton.SetTitleColor(UIColor.Blue, UIControlState.Normal);
            _myQueryStateButton.TouchUpInside += BtnZoomToFeatures_Click;

            // Create the results label and the search bar
            _myResultsLabel = new UILabel() { TextColor = UIColor.Red };
            _myStateEntry = new UISearchBar() { Placeholder = "e.g. NH" };

            // Allow the search bar to dismiss the keyboard
            _myStateEntry.SearchButtonClicked += (sender, e) =>
            {
                _myStateEntry.EndEditing(true);
            };

            // Add views to the page
            View.AddSubviews(_myMapView, _myQueryExtentButton, _myQueryStateButton, _myResultsLabel, _myStateEntry);
        }

        public override void ViewDidLoad()
        {
            CreateLayout();
            Initialize();

            base.ViewDidLoad();
        }

        public override void ViewDidLayoutSubviews()
        {
            var topMargin = NavigationController.NavigationBar.Frame.Height + UIApplication.SharedApplication.StatusBarFrame.Height + 10;

            // Setup the visual frame for the MapView
            _myMapView.Frame = new CoreGraphics.CGRect(0, 0, View.Bounds.Width, View.Bounds.Height);

            // Place extent button
            _myQueryExtentButton.Frame = new CoreGraphics.CGRect(10, topMargin + 25, View.Bounds.Width / 2 - 15, 20);

            // Place state button
            _myQueryStateButton.Frame = new CoreGraphics.CGRect(View.Bounds.Width / 2 + 5, topMargin + 25, View.Bounds.Width / 2 - 15, 20);

            // Place state text field
            _myStateEntry.Frame = new CoreGraphics.CGRect(10, topMargin, View.Bounds.Width - 20, 20);

            // Place result label
            _myResultsLabel.Frame = new CoreGraphics.CGRect(10, topMargin + 50, View.Bounds.Width - 20, 20);

            base.ViewDidLayoutSubviews();
        }
    }
}


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