public class SampleProjectData
    {
        public static ObservableCollection<Product> GetSampleData()
        {
            DateTime dtS = DateTime.Now;
            ObservableCollection<Product> teams = new ObservableCollection<Product>();
            teams.Add(new Product() { PDName = "Product1", OverallStartTime = dtS, OverallEndTime = dtS + TimeSpan.FromDays(3),  });
            Project emp = new Project() { PName = "Project1", OverallStartTime = dtS + TimeSpan.FromDays(1), OverallEndTime = dtS + TimeSpan.FromDays(6)  };
            emp.Tasks.Add(new Task() { StartTime = dtS, EndTime = dtS + TimeSpan.FromDays(2), TaskName = "John's Task 3" });
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(3), EndTime = dtS + TimeSpan.FromDays(4), TaskName = "John's Task 2" });
            teams[0].Projects.Add(emp);
            emp = new Project() { PName = "Project2", OverallStartTime = dtS + TimeSpan.FromDays(1.5), OverallEndTime = dtS + TimeSpan.FromDays(5.5) };
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(1), EndTime = dtS + TimeSpan.FromDays(4), TaskName = "Victor's Task" });
            teams[0].Projects.Add(emp);
            emp = new Project() { PName = "Project3", OverallStartTime = dtS + TimeSpan.FromDays(2), OverallEndTime = dtS + TimeSpan.FromDays(5) };
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(1), EndTime = dtS + TimeSpan.FromDays(4), TaskName = "Jason's Task 1" });
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(7), EndTime = dtS + TimeSpan.FromDays(9), TaskName = "Jason's Task 2" });
            teams[0].Projects.Add(emp);
            teams.Add(new Product() { PDName = "Product2", OverallStartTime = dtS, OverallEndTime = dtS + TimeSpan.FromDays(3) });
            emp = new Project() { PName = "Project4", OverallStartTime = dtS + TimeSpan.FromDays(0.5), OverallEndTime = dtS + TimeSpan.FromDays(3.5) };
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(1.5), EndTime = dtS + TimeSpan.FromDays(4), TaskName = "Vicky's Task" });
            teams[1].Projects.Add(emp);
            emp = new Project() { PName = "Project5", OverallStartTime = dtS + TimeSpan.FromDays(2), OverallEndTime = dtS + TimeSpan.FromDays(6) };
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(2.2), EndTime = dtS + TimeSpan.FromDays(3.8), TaskName = "Oleg's Task 1" });
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(5), EndTime = dtS + TimeSpan.FromDays(6), TaskName = "Oleg's Task 2" });
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(8), EndTime = dtS + TimeSpan.FromDays(9.6), TaskName = "Oleg's Task 3" });
            teams[1].Projects.Add(emp);
            emp = new Project() { PName = "Project6", OverallStartTime = dtS + TimeSpan.FromDays(2.5), OverallEndTime = dtS + TimeSpan.FromDays(4.5) };
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(0.8), EndTime = dtS + TimeSpan.FromDays(2), TaskName = "Kim's Task" });
            teams[1].Projects.Add(emp);
            teams.Add(new Product() { PDName = "Product3", OverallStartTime = dtS, OverallEndTime = dtS + TimeSpan.FromDays(3) });
            emp = new Project() { PName = "Project7", OverallStartTime = dtS + TimeSpan.FromDays(5), OverallEndTime = dtS + TimeSpan.FromDays(7.5) };
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(1.5), EndTime = dtS + TimeSpan.FromDays(4), TaskName = "Balaji's Task 1" });
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(5), EndTime = dtS + TimeSpan.FromDays(8), TaskName = "Balaji's Task 2" });
            teams[2].Projects.Add(emp);
            emp = new Project() { PName = "Project8", OverallStartTime = dtS + TimeSpan.FromDays(3), OverallEndTime = dtS + TimeSpan.FromDays(6.3) };
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(1.75), EndTime = dtS + TimeSpan.FromDays(2.25), TaskName = "Li's Task" });
            teams[2].Projects.Add(emp);
            emp = new Project() { PName = "Project9", OverallStartTime = dtS + TimeSpan.FromDays(2), OverallEndTime = dtS + TimeSpan.FromDays(6) };
            emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(2), EndTime = dtS + TimeSpan.FromDays(3), TaskName = "Stacy's Task" });
            teams[2].Projects.Add(emp);
            return teams;
        }
    }
above is an sample data where i am grouping them with static data in the same  way i need  to  for teh data  which is cmg from DB  and i need to store them  list
all these three data  are comig from different services. and i am storing them in a list 
 now i have  three tables  data
Product ,
Project,
Task.
all the data are  coming from  webservies.
 i have  created three list  where i am storing the data in  list.
Listobjpro= new List();
Listobjproduct= new List();
LIstobjTask= new List(); 
now  what i need  to  do is  i need  to  do the mapping between these tables. 
if  you see above. i have  object of Product under Product i have  added object of  Project
 and then under project object i have  added task object. 
 now  from the above  data which is  stored in the list i need to do the same mapping  between class.
and  group  the data.
public class Product : INotifyPropertyChanged
    {
        public Product()
        {
            this.Projects = new ObservableCollection<Project>();
        }
        public string PDName { get; set; }
        public ObservableCollection<Project> Projects { get; set; }
        private DateTime _st;
        public DateTime OverallStartTime
        {
            get { return _st; }
            set
            {
                if (this._st != value)
                {
                    TimeSpan dur = this._et - this._st;
                    this._st = value;
                    this.OnPropertyChanged("OverallStartTime");
                    this.OverallEndTime = value + dur;
                }
            }
        }
        private DateTime _et;
        public DateTime OverallEndTime
        {
            get { return _et; }
            set
            {
                if (this._et != value)
                {
                    this._et = value;
                    this.OnPropertyChanged("OverallEndTime");
                }
            }
        }
        #region INotifyPropertyChanged Members
        protected void OnPropertyChanged(string name)
        {
            if (this.PropertyChanged != null)
                this.PropertyChanged(this, new PropertyChangedEventArgs(name));
        }
        public event PropertyChangedEventHandler PropertyChanged;
        #endregion
    }
    public class Project : INotifyPropertyChanged
    {
        public Project() { this.Tasks = new ObservableCollection<Task>(); }
        public string PName { get; set; }
        public ObservableCollection<Task> Tasks { get; set; }
        DateTime _st;
        public DateTime OverallStartTime
        {
            get { return _st; }
            set
            {
                if (this._st != value)
                {
                    TimeSpan dur = this._et - this._st;
                    this._st = value;
                    this.OnPropertyChanged("OverallStartTime");
                    this.OverallEndTime = value + dur;
                }
            }
        }
        DateTime _et;
        public DateTime OverallEndTime
        {
            get { return _et; }
            set
            {
                if (this._et != value)
                {
                    this._et = value;
                    this.OnPropertyChanged("OverallEndTime");
                }
            }
        }
        #region INotifyPropertyChanged Members
        protected void OnPropertyChanged(string name)
        {
            if (this.PropertyChanged != null)
                this.PropertyChanged(this, new PropertyChangedEventArgs(name));
        }
        public event PropertyChangedEventHandler PropertyChanged;
        #endregion
    }
    public class Task : INotifyPropertyChanged
    {
        public string TaskName { get; set; }
        DateTime _st;
        public DateTime StartTime
        {
            get { return _st; }
            set
            {
                if (this._st != value)
                {
                    TimeSpan dur = this._et - this._st;
                    this._st = value;
                    this.OnPropertyChanged("StartTime");
                    this.EndTime = value + dur;
                }
            }
        }
        private DateTime _et;
        public DateTime EndTime
        {
            get { return _et; }
            set
            {
                if (this._et != value)
                {
                    this._et = value;
                    this.OnPropertyChanged("EndTime");
                }
            }
        }
        #region INotifyPropertyChanged Members
        protected void OnPropertyChanged(string name)
        {
            if (this.PropertyChanged != null)
                this.PropertyChanged(this, new PropertyChangedEventArgs(name));
        }
        public event PropertyChangedEventHandler PropertyChanged;
        #endregion
    }