I'm trying to get a message box to display some simple counts of layers and fields. Everything works fine until I add in the code to get the field count of composite layers. Below is the code for my button click event which populates the message box, and the error message I am receiving.

private void buttonCountLayers_Click(object sender, EventArgs e)
            //count the point/line/poly/raster feature layers
            int groupcount = 0;
            int pointcount = 0;
            int linecount = 0;
            int polycount = 0;
            int rastercount = 0;
            string subfields = "";
            int subfieldcount = 0;

for (int i = 0; i < layercount; i++) { ILayer pLayer = pMap.get_Layer(i); string name = pLayer.Name; pointcount = pointcount + PointLayerTest(pLayer); //returns 1 if layer has point geometry linecount = linecount + LineLayerTest(pLayer); polycount = polycount + PolygonLayerTest(pLayer); rastercount = rastercount + RasterLayerTest(pLayer); if (pLayer is ICompositeLayer) { ICompositeLayer pCompLayer = pLayer as ICompositeLayer; //QI int sublayern = pCompLayer.Count; for (int j = 0; j < sublayern; j++) //go through group layer { ILayer pLayer2 = pCompLayer.get_Layer(j); groupcount = groupcount + GroupLayerTest(pLayer2); pointcount = pointcount + PointLayerTest(pLayer2); linecount = linecount + LineLayerTest(pLayer2); polycount = polycount + PolygonLayerTest(pLayer2); rastercount = rastercount + RasterLayerTest(pLayer2); IFeatureLayer2 pFeatureLayer = (IFeatureLayer2)pLayer2; ITable subLayers = (ITable)pFeatureLayer; subfieldcount = subLayers.Fields.FieldCount; //this line throws the error subfields = subfields + Environment.NewLine + pLayer2.Name + ":" + subfieldcount; } } } //show all counts in pop-up window MessageBox.Show("number of group layers:"+groupcount+ Environment.NewLine +"point layers:"+pointcount+ Environment.NewLine+"line layers:"+linecount+Environment.NewLine+"polygon layers:"+polycount+ Environment.NewLine+"raster layers:"+rastercount+Environment.NewLine+Environment.NewLine+subfields); }

ERROR MESSAGE: An unhandled exception of type 'System.Runtime.InteropServices.COMException' occurred in projectname.dll

Additional information: Error HRESULT E_FAIL has been returned from a call to a COM component.

1 Answer 1


It's difficult to tell not knowing what layers you are in your map, but this code: rastercount = rastercount + RasterLayerTest(pLayer2); makes it look like you are expecting an IRasterLayer.

I do not believe you can get an IFeatureLayer from a Raster layer. Try testing for IRasterLayer and skip over it.


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