private void lstTask_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            if (lstTask.SelectedIndex == -1)
            {
                return;
            }
            txtDesc.Document.Blocks.Clear();
            txtRemark.Document.Blocks.Clear();

            Task task = (Task)lstTask.SelectedItem;

            txtTaskName.Text = task.TaskName;
            txtDesc.AppendText(task.TaskDesc);
            dtpDueDate.SelectedDateTime = task.DueDate;

            TasksHelper client = new TasksHelper();

            TaskAssignment assn = client.GetTaskAssignment(task.TaskID, event_.EventID,
                int.Parse(cboRole.SelectedValue.ToString()));

            txtRemark.AppendText(assn.Remarks);
             chkIsCompleted.IsChecked = this.txtRemark.IsReadOnly = assn.IsCompleted;

            chkIsCompleted.IsEnabled = !assn.IsCompleted;

            if (!assn.IsRead)
            {
                client.SetTaskRead(task, int.Parse(cboRole.SelectedValue.ToString()));
            }
            client.Close();
        }