Group By Query in Linq

 Group By Query Example in Linq
 
  public DataTable GetApprovedLeaveData(int emp_id)
        {

            DataClassesHrPortalDataContext dc1 = new DataClassesHrPortalDataContext(dbConnStr);
            var obj = from tsk in dc1.Tasks
                      join lvr in dc1.Leave_Requests on tsk.task_id equals lvr.Task_Id

                      where tsk.requested_by == emp_id && tsk.substatus == "Approved"
                      group lvr by new { tsk.requested_by, lvr.Leave_Type } into grp
                      select new { grp.Key.requested_by, grp.Key.Leave_Type, ndays = grp.Sum(lvr => lvr.ndays) };


            IDbCommand objCmd = dc1.GetCommand(obj as IQueryable);
            SqlDataAdapter objAdpt = new SqlDataAdapter();
            objAdpt.SelectCommand = (SqlCommand)objCmd;
            DataTable objDt = new DataTable();
            try
            {
                objCmd.Connection.Open();
                objAdpt.Fill(objDt);
            }
            finally
            {
                objCmd.Connection.Close();
            }
            return objDt;

        }