I had a bit of trouble running this down. Thought it might help someone.
IMxDocument pMxDoc = (IMxDocument)ArcMap.Application.Document;
IContentsView pTOC = pMxDoc.CurrentContentsView;
IFeatureLayer exportLayer = (IFeatureLayer)pTOC.SelectedItem; // Selected Layer
if (!exportAll)
{
IFeatureLayerDefinition iDefLayer = (IFeatureLayerDefinition)pTOC.SelectedItem;
exportLayer = iDefLayer.CreateSelectionLayer(pTOC.Name, true, null, null); // Selected features
}
Geoprocessor gp = new Geoprocessor();
gp.OverwriteOutput = true;
gp.AddOutputsToMap = false;
LayerToKML layerToKML = new LayerToKML();
layerToKML.layer = exportLayer;
layerToKML.layer_output_scale = 10000;
layerToKML.out_kmz_file = fileName;
try {
object result = gp.Execute(layerToKML, null);
messages = new string[gp.MessageCount];
for (int i = 0; i < gp.MessageCount; i++)
{
messages = gp.GetMessage(i);
}
return true;
}
catch (Exception ex) {
messages = new string[gp.MessageCount];
for (int i = 0; i < gp.MessageCount; i++)
{
_logger.Error($"GP Message #{i} :"+gp.GetMessage(i));
}
return false;
}