title: How to implement 3 tiers architecture in c#
body: <p>I read many articles talk about 3 tiers architecture in c# but i see that:</p>
  
  <ul>
  <li><p>Almost use Bussiness Logic Layer(BLL) as a object mapping corresponding table in database. This BLL object has some methods like these:</p>
  
  <p>+<code>GetData()</code>: return this;</p>
  
  <p>+<code>Update(this)</code>;</p>
  
  <p>+<code>Insert(this)</code>;</p>
  
  <p>+<code>Delete(this)</code>;</p></li>
  <li><p>This BLL object calls corresponding DAL(Data Access Layer) to execute to corresponding table of database.</p></li>
  <li>I think if with above methods, we can oly get a record and update it. But if we have got many records and want to put it into a dataset,
  how can we update all records changed? Must we use loop for all records to do that?</li>
  <li>Moreover, in the database, there are many tables related to each other, so how can we put them into dataset, make relations and
  add, update, delete records like using <code>BindingSource</code> with a <code>Combobox</code> and a <code>DataGridView</code>? And how can we seperate code in this situation?</li>
  </ul>