Putting features (IFeature) into ifeatureclass with ArcGIS Engine?

Question

I am trying to get the selected features from axMapControl and put them in a new feature class. I can get the selected features but when i'm trying to put them in a IFeatureClass and then cast it as IFeatureLayer I get the null reference exception.

Can any one help?

List<IFeature> features = GetSelectedFeatures(axMapControl1.get_Layer(0) as IFeatureLayer);
        IPointArray pa = new PointArrayClass();
        for (int i = 0; i < features.Count; i++)
        {
            p.Add(features[i].ShapeCopy as IPoint);
            pa.Add(p[i]);
        }


        IPolyline pl = new PolylineClass();
        pl.FromPoint = pa.Element[0];
        pl.ToPoint = pa.Element[1];
        pl.ToPoint = pa.Element[2];

        pl.SpatialReference = p[0].SpatialReference;

        IWorkspaceFactory workspaceFactory = new ShapefileWorkspaceFactoryClass();
        IWorkspace workspace = workspaceFactory.OpenFromFile(@"C:\", 0);
        IFeatureWorkspace featureWorkspace = workspace as IFeatureWorkspace;

        IFeatureClass FC = CreateFeatureClass("FC", featureWorkspace, pa.get_Element(0).SpatialReference);

        IFeatureCursor fCur = FC.Insert(false);
        IFeatureBuffer buff = FC.CreateFeatureBuffer();

        buff.Shape = pl;
        fCur.InsertFeature(buff);

        fCur.Flush();
        System.Runtime.InteropServices.Marshal.FinalReleaseComObject(fCur);
        ILayer layer =FC as ILayer;
        axMapControl1.AddLayer(layer);

        axMapControl1.Refresh();

Answer 1

You can not cast a FeatureClass into a ILayer! Here's the proper way to reach an ILayer from a FeatureClass:

....
IFeatureLayer fl = new ESRI.ArcGIS.Carto.FeatureLayer() 
fl.FeatureClass  = FC;
var l = fl as ILayer;
axMapControl1.AddLayer(l);

I am assuming all of your previous methods are correct and you have a valid IFeatuerClass (FC).