IFeatureLayerDefinition2 featureDefinition = (IFeatureLayerDefinition2)featureLayer; IQueryFilter queryFilter = new QueryFilterClass(); queryFilter.WhereClause = featureDefinition.DefinitionExpression; queryFilter.SubFields = "*"; IFeatureClass featureClass = featureLayer.FeatureClass; IDataset dataset = (IDataset)featureClass; IFeatureClassName inFCName = (IFeatureClassName)dataset.FullName;