原文
注意需要在编辑模式下进行snapping的添加（也即先需要使用IEngineEditor进入编辑状态）：
IMapControl3 mMap = (IMapControl3)((IToolbarControl)toolHook).Buddy;IEngineEditor m_engineEditor = new EngineEditorClass();if (m_engineEditor.EditState == esriEngineEditState.esriEngineStateNotEditing){//Start editing the workspace of the first feature layer found. ILayer currentLayer = mMap.get_Layer(0);if (currentLayer is IFeatureLayer){ IFeatureLayer featureLayer = currentLayer as IFeatureLayer; IDataset dataset = featureLayer.FeatureClass as IDataset; IWorkspace workspace = dataset.Workspace; m_engineEditor.StartEditing(workspace, mMap.Map); ((IEngineEditLayers)m_engineEditor).SetTargetLayer(featureLayer, 0);}//snappingif (mMap.LayerCount != 0){ IEngineEditor editor = new EngineEditorClass(); IEngineEditLayers editLayers = editor as IEngineEditLayers; IEngineSnapEnvironment snapEnvironment = editor as IEngineSnapEnvironment; IEngineFeatureSnapAgent featureSnapAgent = new EngineFeatureSnap(); featureSnapAgent.FeatureClass = ((IFeatureLayer)mMap.get_Layer(0)).FeatureClass; ; featureSnapAgent.HitType = esriGeometryHitPartType.esriGeometryPartVertex | esriGeometryHitPartType.esriGeometryPartBoundary | esriGeometryHitPartType.esriGeometryPartEndpoint; snapEnvironment.AddSnapAgent(featureSnapAgent); }