The method of GetFeatures from layers, and the problem of invalid transfer range parameters

[wxdlt]

In Class Layer: public override IEnumerable<IFeature> GetFeatures(MRect extent, double resolution) { return _cache.ToList(); }

I want to display the special symbols of the selected features in the layer, but this method can only obtain the features currently displayed in the map.

I try to obtain the elements of the corresponding range through the following methods, but the obtained results cannot be applied with symbolic.

 public  IEnumerable<IFeature> GetFeatures(MRect rect=null)
    {
        if (_layer==null)
        {
            return null;
        }
        if (rect==null)
        {
            rect = _layer.Extent;
        }
        FetchInfo fetchInfo = new FetchInfo(rect, 1);

        return (_layer as Layer).DataSource.GetFeaturesAsync(fetchInfo).Result;
    }

public ThemeStyle CreateThemeStyle(string colorName, List<IFeature> SelectedFeature) { return new ThemeStyle(feature => { VectorStyle style ;

              style = new VectorStyle();
              style.Fill = new Brush(Color.FromString(colorName));
              style.Outline = new Pen(Color.Black);

    //The elements are obtained through  GetFeatures of method, but they are not the same. The following judgment is always false
            if (SelectedFeature.Contains(feature))
            {
                style.Outline.Width = 2;
                style.Outline.Color = Color.Blue;
            }
            return style;
        });
    }

Can you help me solve this problem, thank you

[pauldendulk]

I want to display the special symbols of the selected features in the layer

I don't understand what you are trying to do exactly. Do you want a list of all symbols and show them somewhere outside the map? Or do you want to select a certain set of symbols within the map?

[wxdlt]

I want to get the FID or Objectid of the Feature

[wxdlt]

in ShapeFile Class ,Add one code " feature["FID"] = index;"

public Task<IEnumerable<IFeature>> GetFeaturesAsync(FetchInfo fetchInfo)
        {
            lock (_syncRoot)
            {
                Open();
                try
                {
                    //Use the spatial index to get a list of features whose BoundingBox intersects bbox
                    var objectList = GetObjectIDsInViewPrivate(fetchInfo.Extent);
                    var features = new List<GeometryFeature>();

                    foreach (var index in objectList)
                    {
                        var feature = _dbaseFile?.GetFeature(index, features);
                        if (feature != null)
                        {
                            feature["FID"] = index;
                            feature.Geometry = ReadGeometry(index);
                            if (feature.Geometry?.EnvelopeInternal == null) continue;
                            if (!feature.Geometry.EnvelopeInternal.Intersects(fetchInfo.Extent.ToEnvelope())) continue;
                            if (FilterDelegate != null && !FilterDelegate(feature)) continue;
                            features.Add(feature);
                        }
                    }
                    return Task.FromResult((IEnumerable<IFeature>)features);
                }
                finally
                {
                    Close();
                }
            }
        }

[pauldendulk]

Sorry that we never answered this.

I think this is your problem:

//The elements are obtained through  GetFeatures of method, but they are not the same. The following judgment is always false
if (SelectedFeature.Contains(feature))

Instead you could do:

if (SelectedFeature["FID"] == feature["FID"])

Perhaps you need a cast.