i gt prob with this code

not realli understand the code in the linked list in this program http://www.c-harpcorner.com/1/pbrush.asp can you tell me wat is this code is about? using System; using System.Runtime.Serialization; namespace workflowTool { ///

/// Summary description for LinkedList. ///

public class LinkedList { internal class Node { internal object m_ObjectToStore; internal Node m_Next; internal Node m_Previous; public Node(object objectToStore) { m_ObjectToStore = objectToStore; } } Node m_First; internal uint m_uiNumOfObjects; // These members are used to optimize enumeration. Another way could have been to // iterate till required node is found (which is costly). internal long m_lLastAccessed; internal Node m_LastAccessed; public LinkedList() { // // TODO: Add constructor logic here // m_First = null; m_uiNumOfObjects = 0; m_lLastAccessed = -1; } public void AddToEnd(object objToAdd) { if (m_First == null) { m_First = new Node(objToAdd); m_First.m_Next = m_First; m_First.m_Previous = m_First; ++m_uiNumOfObjects; return; } Node newNode = new Node(objToAdd); // Get the previous node. Node last = m_First.m_Previous; newNode.m_Next = last.m_Next; newNode.m_Previous = last.m_Previous; last.m_Next = newNode; m_First.m_Previous = newNode; ++m_uiNumOfObjects; } public void Clear() { m_First = null; m_uiNumOfObjects = 0; m_lLastAccessed = -1; } public uint Count { get { return m_uiNumOfObjects; } } public object this[uint uiIndex] { get { if (m_LastAccessed == null) { m_LastAccessed = m_First; m_lLastAccessed = 0; return m_First.m_ObjectToStore; } if (uiIndex < 0 || uiIndex >= m_uiNumOfObjects) { throw new IndexOutOfRangeException(); } ++m_lLastAccessed; m_LastAccessed = m_LastAccessed.m_Next; return m_LastAccessed.m_ObjectToStore; } } } } /**************************************************************************** public void OnMouseDown(object source, MouseEventArgs evtArgs) { // Here the draw action has started. if(count==0) { m_Start = new Point(evtArgs.X, evtArgs.Y); m_ShapeBeingDrawn = true; //this.MouseUp += new MouseEventHandler(OnMouseUp); //this.MouseMove += new MouseEventHandler(OnMouseMove); childObj.gObj.setSelect(false); childObj.gObj.setCount(-1); s[arrSize]=new Point(evtArgs.X, evtArgs.Y); arrSize=arrSize+1; //this.label1.Text=arrSize.ToString(); } } public void OnMouseUp(object source, MouseEventArgs evtArgs) { try { Shape shapeDrawn = GetShape(source, evtArgs); if (m_ShapesList == null) { m_ShapesList = new LinkedList(); } m_PreviousShape = null; m_ShapesList.AddToEnd(shapeDrawn); m_ShapeBeingDrawn = false; } catch(Exception e) { MessageBox.Show(e.Message); } } public void OnMouseMove(object source, MouseEventArgs evtArgs) { if (!m_ShapeBeingDrawn) { return; } if (m_PreviousShape != null) { m_PreviousShape.Draw(this); } m_PreviousShape = GetShape(source, evtArgs); m_PreviousShape.Draw(this); } /**************************************************************************** this.MouseDown += new MouseEventHandler(OnMouseDown); this.MouseUp += new MouseEventHandler(OnMouseUp); this.MouseMove += new MouseEventHandler(OnMouseMove);