Below is the code from a Windows service that I wrote a while back. I fully qualified the class names to avoid confusion with the old Geoprocessor class in the Geoprocessing library. ESRI.ArcGIS.ConversionTools.FeatureClassToFeatureClass fcToFcTool = new ESRI.ArcGIS.ConversionTools.FeatureClassToFeatureClass();
fcToFcTool.in_features = featureLayer;
fcToFcTool.out_path = outputDirectory;
fcToFcTool.out_name = newTableName;
if (!string.IsNullOrEmpty(query))
fcToFcTool.where_clause = query;
Geoprocessor gp = new ESRI.ArcGIS.Geoprocessor.Geoprocessor();
gp.Execute(fcToFcTool, null);