ArcGIS Pro 2.6 API Reference Guide
GetFeatures Method
Example 

ArcGIS.Desktop.Mapping Namespace > MapView Class : GetFeatures Method
The geometry used to identify features that intersect it.
Indicates whether only features that visibly intersect the geometry should be returned.
This parameter only applies to 2D. Indicates whether only features that are completely within the geometry should be returned.
Return features that intersect a geometry. This method must be called on the MCT. Use QueuedTask.Run.
Syntax

Parameters

geometry
The geometry used to identify features that intersect it.
visualIntersect
Indicates whether only features that visibly intersect the geometry should be returned.
whollyWithin
This parameter only applies to 2D. Indicates whether only features that are completely within the geometry should be returned.

Return Value

The collection of layers and object ids that intersect the geometry.
Exceptions
ExceptionDescription
This method or property must be called within the lambda passed to QueuedTask.Run.
3D views only support selecting features interactively using geometry in screen coordinates relative to the top-left corner of the view
Example
Create a tool that allows you to sketch in the view and return the features that intersect the sketch.
/*

   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 System.Text;
using System.Threading.Tasks;
using ArcGIS.Core.Geometry;
using ArcGIS.Desktop.Mapping;
using ArcGIS.Desktop.Framework.Threading.Tasks;
using ArcGIS.Desktop.Framework.Dialogs;

namespace Examples
{
  class CustomIdentify : MapTool
  {
    public CustomIdentify()
    {
      IsSketchTool = true;
      SketchType = SketchGeometryType.Rectangle;

      //To perform a interactive selection or identify in 3D or 2D, sketch must be created in screen coordinates.
      SketchOutputMode = SketchOutputMode.Screen;
    }

    protected override Task<bool> OnSketchCompleteAsync(Geometry geometry)
    {
      return QueuedTask.Run(() => 
      {
        var mapView = MapView.Active;
        if (mapView == null)
          return true;

        //Get all the features that intersect the sketch geometry and flash them in the view. 
        var results = mapView.GetFeatures(geometry);
        mapView.FlashFeature(results);

        //Show a message box reporting each layer the number of the features.
        MessageBox.Show(String.Join("\n", results.Select(kvp => String.Format("{0}: {1}", kvp.Key.Name, kvp.Value.Count()))), "Identify Result");
        return true;
      });
    }
  }
}
Requirements

Target Platforms: Windows 10, Windows 8.1, Windows 7

See Also

Reference

MapView Class
MapView Members