How to determine if a LYR file has more than one Layer using ArcObjects?

Question

In using arcpy, I have found that there are just a few lines of code needed to get a list of layers in a LYR file if more than one layer exist. How can I accomplish this same feat using ArcObjects in C#? I know that ILayerFile is the way to start this off and I can open a specific layer file using ILayerFile.Open() but how can I get back a list of layers in this layer file if more than one exist?

Answer 1

Query interface from ILayerFile.Layer to ICompositeLayer to determine whether the layer is a group/composite layer.

If the QI succeded, check ICompositeLayer.Count to see if it has any sublayers.

e.g.:

ILayerFile layerFile = new LayerFileClass();
layerFile.Open(layerFilePath);
ICompositeLayer compositeLayer = layerFile.Layer as ICompositeLayer;
if (compositeLayer != null && compositeLayer.Count > 0)
{
    // do something with the sublayers
}

You can then access a sublayer by its index (probably using a for loop) using the ICompositeLayer.Layer property, which, because it takes an argument should be called as a method in .NET, e.g.: compositeLayer.get_Layer(i).

If you think the layer file might have multiple nested group layers, you would want to write a recursive function to loop through each sublayer and recurse if it is also a composite layer or do something else with it if not.