ArcGIS Pro 3.4 API Reference Guide
ArcGIS.Desktop.Mapping Namespace / MapView Class / GetViewSize Method
Example Version

GetViewSize Method (MapView)
Returns the current size of the view.
Syntax
public Size GetViewSize()

Return Value

The current size of the view.
Example
Use MapView Selection SelectFeaturesEx or GetFeaturesEx
//var featSceneLayer = ...;
var sname = featSceneLayer.Name;

await QueuedTask.Run(() =>
{
  //Select all features within the current map view
  var sz = MapView.Active.GetViewSize();

  var c_ll = new Coordinate2D(0, 0);
  var c_ur = new Coordinate2D(sz.Width, sz.Height);
  //Use screen coordinates for 3D selection on MapView
  var env = EnvelopeBuilderEx.CreateEnvelope(c_ll, c_ur);

  //HasAssociatedFeatureService does not matter for SelectFeaturesEx
  //or GetFeaturesEx
  var result = MapView.Active.SelectFeaturesEx(env);
  //var result = MapView.Active.GetFeaturesEx(env);

  //The list of object ids from SelectFeaturesEx
  //At 2.x - var oids1 = result.Where(kvp => kvp.Key.Name == sname).First().Value;
  var oids1 = result.ToDictionary().Where(kvp => kvp.Key.Name == sname).First().Value;
  //TODO - use the object ids

  MapView.Active.Map.ClearSelection();
});
Use Select or Search with a Spatial Query
//var featSceneLayer = ...;
//var sname = featSceneLayer.Name;
await QueuedTask.Run(() =>
{
  if (!featSceneLayer.HasAssociatedFeatureService)
    return;//no search or select

  //Select all features within the current map view
  var sz = MapView.Active.GetViewSize();
  var map_pt1 = MapView.Active.ClientToMap(new System.Windows.Point(0, sz.Height));
  var map_pt2 = MapView.Active.ClientToMap(new System.Windows.Point(sz.Width, 0));

  //Convert to an envelope
  var temp_env = EnvelopeBuilderEx.CreateEnvelope(map_pt1, map_pt2, MapView.Active.Map.SpatialReference);

  //Project if needed to the layer spatial ref
  SpatialReference sr = null;
  using (var fc = featSceneLayer.GetFeatureClass())
  using (var fdef = fc.GetDefinition())
    sr = fdef.GetSpatialReference();

  var env = GeometryEngine.Instance.Project(temp_env, sr) as Envelope;

  //Set up a query filter
  var sf = new SpatialQueryFilter()
  {
    FilterGeometry = env,
    SpatialRelationship = SpatialRelationship.Intersects,
    SubFields = "*"
  };

  //Select against the feature service
  var select = featSceneLayer.Select(sf);
  if (select.GetCount() > 0)
  {
    //enumerate over the selected features
    using (var rc = select.Search())
    {
      while (rc.MoveNext())
      {
        using (var feature = rc.Current as Feature)
        {
          var oid = feature.GetObjectID();
          //etc.
        }
      }
    }
  }

  MapView.Active.Map.ClearSelection();

});
Requirements

Target Platforms: Windows 11, Windows 10

ArcGIS Pro version: 3 or higher.
See Also