OK, I've been labeling using the LabelEngine and simple expressions and it is working for every layer. I want to offer the option of labeling only selected features and thought it would be this simple:
annotateLayerProperties.LabelWhichFeatures = esriLabelWhichFeatures.esriSelectedFeatures;
Unfortunately that doesn't do it. Every polygon is still labeled. I verified that the features were selected (I have a routine that just returns the selected keys.) I also tried replacing the Engine labeling with a:
annotateLayerProperties.WhereClause = BuildWhere( keyName, selected );
using both my keys and the features OIDs - that does not label at all.
Does anyone know how to label only the selected features?