title: Populate ComboBox2 depending on Combobox1 selected item
body: <p>i am a student, and a newbie to programming, i have two comboboxes, combobox1 and combobox2 combobox1 contains mobile company's like nokia,samsung,htc and combobox2 contains mobile models like samsung,s3 and etc, i want to sort the two combobox i mean when i click the nokia in the combobox1 then all the model of nokia should be visible in the list of combobo2, so i have decided to used foreign key relationship</p>
  
  <pre><code>          Manufacturer -table
          - manufacturerid (primary key)
          - name
  
           Model -table
          - modelid (primary key)
          - manufacturerid (foreign key to manufacturer)
           - name
  </code></pre>
  
  <p>Example for the data:</p>
  
  <p>Manufacturer table</p>
  
  <pre><code>         manufacturerid name
       -------------- ----------
      1              Nokia
      2              Samsung
      3              HTC
  </code></pre>
  
  <p>Model table</p>
  
  <pre><code>       modelid manufacturerid name
       ------- -------------- ----------
       1       1              C7
       2       1              Lumia 900
       3       1              Lumia 920
       4       2              Galaxy S II
       5       2              Galaxy S III
       6       3              Desire X
       7       3              Windows Phone 8X
       8       3              One S
  </code></pre>
  
  <p>i want that if i select nokia in the first combobox then the second combobox will select all the models which are manufactureid = 1
  what to use? how can i do that?
  priviously i was using </p>
  
  <pre><code> private void comboBox4_SelectedIndexChanged(object sender, EventArgs e)
    {
       comboBox3.Text = "";
     if ("samsung" == comboBox4.SelectedItem.ToString())
        {
             comboBox3.DataSource = table1BindingSource;
             comboBox3.ValueMember = "samsung";
             comboBox3.DisplayMember = "samsung";
        }
     if ("htc" == comboBox4.SelectedItem.ToString())
        {
           comboBox3.DataSource = table1BindingSource;
           comboBox3.ValueMember = "htc";
            comboBox3.DisplayMember = "htc";
         }
    }
  </code></pre>
  
  <p>but i have to update the samsung string each time i add a new model, so i decided to work with tables so that i can update that</p>