/// <summary>
/// togle the state of given task
/// </summary>
/// <param name="t"></param>
private void toggleCopleteTask(TaskItemViewModel t)
{
t.Completed = !t.Completed;
UpdateCounts();
}
/// <summary>
/// delete given task
/// </summary>
/// <param name="t"></param>
private void deleteTask(TaskItemViewModel t)
{
Tasks.Remove(t);
UpdateCounts();
}
