How to create a new IEnumLayer object?

ericliprandi

Hi,

I am trying to filter an IEnumLayer to only contain visible layers. I want to pass this to IFeatureCache2.AddLayers(...). I could not find any public implementations of IEnumLayer. Since we are in C# I wrote a couple of extension methods that convert IEnumLayer to IEnumerable<ILayer> and vice-versa. But passing my custom implementation of IEnumLayer did not seem to make AddLayers(...) happy.

Here is my extensions class:

    public static class EnumLayerExtensions
    {
        public static IEnumerable<ILayer> AsEnumerable(this IEnumLayer layers)
        {
            layers.Reset();
            var layer = layers.Next();
            while (layer != null)
            {
                yield return layer;
                layer = layers.Next();
            }
        }


        public static IEnumLayer ToEnumLayer(this IEnumerable<ILayer> layers)
        {
            return new EnumLayerWrapper(layers);
        }


        private class EnumLayerWrapper : IEnumLayer
        {
            private readonly ILayer[] _layers;
            private int _index;


            public EnumLayerWrapper(IEnumerable<ILayer> layers)
            {
                _layers = layers.ToArray();
                _index = 0;
            }


            public ILayer Next()
            {
                return _index < _layers.Length ? _layers[_index++] : null;
            }


            public void Reset()
            {
                _index = 0;
            }
        }
    }

using this I can then write the following code:

var visibleLayers = Map.Layers.AsEnumerable().Where(l=>l.Visible);


var cache = new FeatureCacheClass() as IFeatureCache2;


cache.Initialize(point,radius);


cache.AddLayers(visibleLayers.ToEnumLayer(), null);

In the above code, line 04 will just run for ever as-is. If I use the layers straight from the Map, it comes back fairly fast. I have written a handful of unit tests to validate my implementation of ToEnumLayer() and they all seem to pass. Based on all this, I have a couple of questions:

1. Is there an out of the box implementation of IEnumLayer that I can use to filter visible layers only to pass to IFeatureCache2.AddLayers()?
2. What's wrong with my implementation of IEnumLayer?

Thanks in advance for any help,

Eric.

Anonymous User

Eric,

You'll probably find its looping through the ILayer Next implementation.

You'll need to throw an exception there rather than return null.

    public ILayer Next()
    {
      if (index < layers.Count)
        return layers[index++];
      else
        throw new Exception();
    }