Custom reshape polyline edit task
EngineEditTask\ReshapePolylineEditTask.cs
// Copyright 2012 ESRI
// 
// All rights reserved under the copyright laws of the United States
// and applicable international laws, treaties, and conventions.
// 
// You may freely redistribute and use this sample code, with or
// without modification, provided you include the original copyright
// notice and use restrictions.
// 
// See the use restrictions.
// 

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

using ESRI.ArcGIS.ADF.CATIDs;
using ESRI.ArcGIS.Controls;
using ESRI.ArcGIS.Geodatabase;
using ESRI.ArcGIS.Geometry;
using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.esriSystem;

namespace ReshapePolylineEditTask_CS
{
    [Guid("89467aa7-76c1-4531-a160-e160e8d782f7")]
    [ClassInterface(ClassInterfaceType.None)]
    [ProgId("ReshapePolylineEditTask_CS.ReshapePolylineEditTask")]
    public class ReshapePolylineEditTask : ESRI.ArcGIS.Controls.IEngineEditTask
    {
        #region Private Members
        IEngineEditor m_engineEditor;
        IEngineEditSketch m_editSketch;
        IEngineEditLayers m_editLayer;
        #endregion

        #region COM Registration Function(s)
        [ComRegisterFunction()]
        [ComVisible(false)]
        static void RegisterFunction(Type registerType)
        {
            // Required for ArcGIS Component Category Registrar support
            ArcGISCategoryRegistration(registerType);
        }

        [ComUnregisterFunction()]
        [ComVisible(false)]
        static void UnregisterFunction(Type registerType)
        {
            // Required for ArcGIS Component Category Registrar support
            ArcGISCategoryUnregistration(registerType);
        }

        #region ArcGIS Component Category Registrar generated code
        /// <summary>
        /// Required method for ArcGIS Component Category registration -
        /// Do not modify the contents of this method with the code editor.
        /// </summary>
        private static void ArcGISCategoryRegistration(Type registerType)
        {
            string regKey = string.Format("HKEY_CLASSES_ROOT\\CLSID\\{{{0}}}", registerType.GUID);
            EngineEditTasks.Register(regKey);

        }
        /// <summary>
        /// Required method for ArcGIS Component Category unregistration -
        /// Do not modify the contents of this method with the code editor.
        /// </summary>
        private static void ArcGISCategoryUnregistration(Type registerType)
        {
            string regKey = string.Format("HKEY_CLASSES_ROOT\\CLSID\\{{{0}}}", registerType.GUID);
            EngineEditTasks.Unregister(regKey);

        }

        #endregion
        #endregion

        #region IEngineEditTask Implementations

        public void Activate(ESRI.ArcGIS.Controls.IEngineEditor editor, ESRI.ArcGIS.Controls.IEngineEditTask oldTask)
        {
            if (editor == null)
                return;

            m_engineEditor = editor;
            m_editSketch = m_engineEditor as IEngineEditSketch;
            m_editSketch.GeometryType = esriGeometryType.esriGeometryPolyline;
            m_editLayer = m_editSketch as IEngineEditLayers; 
           
            //Listen to engine editor events
            ((IEngineEditEvents_Event)m_editSketch).OnTargetLayerChanged += new IEngineEditEvents_OnTargetLayerChangedEventHandler(OnTargetLayerChanged);
            ((IEngineEditEvents_Event)m_editSketch).OnSelectionChanged += new IEngineEditEvents_OnSelectionChangedEventHandler(OnSelectionChanged);
            ((IEngineEditEvents_Event)m_editSketch).OnCurrentTaskChanged += new IEngineEditEvents_OnCurrentTaskChangedEventHandler(OnCurrentTaskChanged);
        }

     
        public void Deactivate()
        {
            m_editSketch.RefreshSketch();
            
            //Stop listening to engine editor events.
            ((IEngineEditEvents_Event)m_editSketch).OnTargetLayerChanged -= OnTargetLayerChanged;
            ((IEngineEditEvents_Event)m_editSketch).OnSelectionChanged -= OnSelectionChanged;
            ((IEngineEditEvents_Event)m_editSketch).OnCurrentTaskChanged -= OnCurrentTaskChanged;

            //Release object references.
            m_engineEditor = null;
            m_editSketch = null;
            m_editLayer = null;
        }

        public string GroupName
        {
            get
            {    
                //This property allows groups to be created/used in the EngineEditTaskToolControl treeview.
                //If an empty string is supplied the task will be appear in an "Other Tasks" group. 
                //In this example the Reshape Polyline_CSharp task will appear in the existing Modify Tasks group.
                return "Modify Tasks";
            }
        }

        public string Name
        {
            get
            {    
                return "Reshape Polyline_CSharp"; //unique edit task name
            }
        }

        public void OnDeleteSketch()
        {
        }

        public void OnFinishSketch()
        {
            //get reference to featurelayer being edited
            IFeatureLayer featureLayer = m_editLayer.TargetLayer as IFeatureLayer;
            //get reference to the sketch geometry
            IGeometry reshapeGeom = m_editSketch.Geometry;

            if (reshapeGeom.IsEmpty == false)
            {
                //get the currently selected feature    
                IFeatureSelection featureSelection = featureLayer as IFeatureSelection;
                ISelectionSet selectionSet = featureSelection.SelectionSet;
                ICursor cursor;
                selectionSet.Search(null, false, out cursor);
                IFeatureCursor featureCursor = cursor as IFeatureCursor;
                //the PerformSketchToolEnabledChecks property has already checked that only 1 feature is selected
                IFeature feature = featureCursor.NextFeature();
                 
                //Take a copy of geometry for the selected feature
                IGeometry editShape = feature.ShapeCopy;

                //create a path from the editsketch geometry
                IPointCollection reshapePath = new PathClass();
                reshapePath.AddPointCollection(reshapeGeom as IPointCollection);

                //reshape the selected feature
                IPolyline polyline = editShape as IPolyline;
                polyline.Reshape(reshapePath as IPath);

                #region Perform an edit operation to store the new geometry for selected feature

                try
                {
                    m_engineEditor.StartOperation();
                    feature.Shape = editShape;
                    feature.Store();
                    m_engineEditor.StopOperation("Reshape Feature");
                }
                catch (Exception ex)
                {
                    m_engineEditor.AbortOperation();
                    System.Diagnostics.Trace.WriteLine(ex.Message, "Reshape Geometry Failed");
                }

                #endregion
            }

            //refresh the display 
            IActiveView activeView = m_engineEditor.Map as IActiveView;
            activeView.PartialRefresh(esriViewDrawPhase.esriViewGeography, (object)featureLayer, activeView.Extent);
          

        }

        public string UniqueName
        {      
            get 
            { 
                return "ReshapePolylineEditTask_Reshape Polyline_CSharp" ;
            }
        }

        #endregion

        #region Event Listeners
        public void OnTargetLayerChanged()
        {
            PerformSketchToolEnabledChecks();
        }

        public void OnSelectionChanged()
        {
            PerformSketchToolEnabledChecks();
        }


        void OnCurrentTaskChanged()
        {
            if (m_engineEditor.CurrentTask.Name == "Reshape Polyline_CSharp")
            {
                PerformSketchToolEnabledChecks();
            }
        }
        #endregion

        #region private methods

        private void PerformSketchToolEnabledChecks()
        {
            if (m_editLayer == null)
                return;

            //Only enable the sketch tool if there is a polyline target layer.
            if (m_editLayer.TargetLayer.FeatureClass.ShapeType != esriGeometryType.esriGeometryPolyline)
            {
                m_editSketch.GeometryType = esriGeometryType.esriGeometryNull;
                return;
            }

            //check that only one feature in the target layer is currently selected
            IFeatureSelection featureSelection = m_editLayer.TargetLayer as IFeatureSelection;
            ISelectionSet selectionSet = featureSelection.SelectionSet;
            if (selectionSet.Count != 1)
            {
                m_editSketch.GeometryType = esriGeometryType.esriGeometryNull;
                return;
            }

            m_editSketch.GeometryType = esriGeometryType.esriGeometryPolyline;

        }

        #endregion

    }
}