Feature layer query

<UserControl x:Class="ArcGIS.WPF.Samples.FeatureLayerQuery.FeatureLayerQuery"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:esri="http://schemas.esri.com/arcgis/runtime/2013">
    <Grid>
        <esri:MapView x:Name="MyMapView" />
        <Border Style="{StaticResource BorderStyle}">
            <StackPanel Orientation="Vertical">
                <TextBlock FontWeight="SemiBold"
                           Text="Enter a state name and click 'Query' to search."
                           TextAlignment="Center"
                           TextWrapping="Wrap" />
                <TextBox x:Name="QueryEntry"
                         Margin="0,5,0,0"
                         Text="New York"
                         TextAlignment="Center" />
                <Button Margin="0,5,0,0"
                        Click="OnQueryClicked"
                        Content="Query" />
            </StackPanel>
        </Border>
    </Grid>
</UserControl>

// 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 Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Symbology;
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Threading.Tasks;
using System.Windows;

namespace ArcGIS.WPF.Samples.FeatureLayerQuery
{
    [ArcGIS.Samples.Shared.Attributes.Sample(
        name: "Feature layer query",
        category: "Data",
        description: "Find features in a feature table which match an SQL query.",
        instructions: "Input the name of a U.S. state into the text field. When you click the button, a query is performed and the matching features are highlighted or an error is returned.",
        tags: new[] { "query", "search" })]
    public partial class FeatureLayerQuery
    {
        // Create reference to service of US States.
        private string _statesUrl = "https://services.arcgis.com/jIL9msH9OI208GCb/arcgis/rest/services/USA_Daytime_Population_2016/FeatureServer/0";

        // Create globally available feature table for easy referencing.
        private ServiceFeatureTable _featureTable;

        // Create globally available feature layer for easy referencing.
        private FeatureLayer _featureLayer;

        public FeatureLayerQuery()
        {
            InitializeComponent();

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

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

            // Create and set initial map location.
            MapPoint initialLocation = new MapPoint(-11000000, 5000000, SpatialReferences.WebMercator);
            myMap.InitialViewpoint = new Viewpoint(initialLocation, 100000000);

            // Create feature table using a URL.
            _featureTable = new ServiceFeatureTable(new Uri(_statesUrl));

            // Create feature layer using this feature table. Make it slightly transparent.
            _featureLayer = new FeatureLayer(_featureTable)
            {
                Opacity = 0.6,
                // Work around service setting.
                MaxScale = 10
            };

            // Create a new renderer for the States Feature Layer.
            SimpleLineSymbol lineSymbol = new SimpleLineSymbol(SimpleLineSymbolStyle.Solid, Color.Black, 1);
            SimpleFillSymbol fillSymbol = new SimpleFillSymbol(SimpleFillSymbolStyle.Solid, Color.Transparent, lineSymbol);

            // Set States feature layer renderer.
            _featureLayer.Renderer = new SimpleRenderer(fillSymbol);

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

            // Adjust the selection color.
            MyMapView.SelectionProperties.Color = Color.Cyan;

            // Assign the map to the MapView.
            MyMapView.Map = myMap;
        }

        private void OnQueryClicked(object sender, RoutedEventArgs e)
        {
            // Remove any previous feature selections that may have been made.
            _featureLayer.ClearSelection();

            // Begin query process.
            _ = QueryStateFeature(QueryEntry.Text);
        }

        private async Task QueryStateFeature(string stateName)
        {
            try
            {
                // Create a query parameters that will be used to Query the feature table.
                QueryParameters queryParams = new QueryParameters();

                // Trim whitespace on the state name to prevent broken queries.
                string formattedStateName = stateName.Trim().ToUpper();

                // Construct and assign the where clause that will be used to query the feature table.
                queryParams.WhereClause = "upper(STATE_NAME) LIKE '%" + formattedStateName + "%'";

                // Query the feature table.
                FeatureQueryResult queryResult = await _featureTable.QueryFeaturesAsync(queryParams);

                // Cast the QueryResult to a List so the results can be interrogated.
                List<Feature> features = queryResult.ToList();

                if (features.Any())
                {
                    // Create an envelope.
                    EnvelopeBuilder envBuilder = new EnvelopeBuilder(SpatialReferences.WebMercator);

                    // Loop over each feature from the query result.
                    foreach (Feature feature in features)
                    {
                        // Add the extent of each matching feature to the envelope.
                        envBuilder.UnionOf(feature.Geometry.Extent);

                        // Select each feature.
                        _featureLayer.SelectFeature(feature);
                    }

                    // Zoom to the extent of the selected feature(s).
                    await MyMapView.SetViewpointGeometryAsync(envBuilder.ToGeometry(), 50);
                }
                else
                {
                    MessageBox.Show("Retry your query with a valid state name, like 'California'.", "State not found!");
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("An error occurred.\n" + ex, "Sample error");
            }
        }
    }
}