title: Mapping values in dropdown
body: <p><strong>Table 1:</strong></p>
  
  <pre><code>ID 
  1
  2
  3 
  4
  5
  6
  7
  8
  9
  0
  </code></pre>
  
  <p>I have to create dropdowns called <code>MasterID</code> &amp; <code>ChildID</code> out of this <code>ID</code> column. <code>MasterID</code> &amp; <code>ChildID</code> will have <code>ID</code> column values based on mapping. Mapping process will be like any values from the <code>ID</code> column can be <code>MasterID</code> or <code>ChildID</code>. But <code>MasterID</code> will have unique <code>ChildID</code>. </p>
  
  <p><strong>Note:</strong> While binding <code>MasterID</code> and <code>ChildID</code> dropdowns it will have <code>ID</code> values on pageload. Once mapping starts then the values should come accordingly. Also I have a Add button in my page and once I select values in two dropdowns and add then they will get saved in the DB. </p>
  
  <p>For ex: If I select the <code>ID</code> value 1 in <code>MasterID</code> and 5 in <code>ChildID</code> and add them to DB, then the next time the value 1 from <code>ID</code> column can come in <code>MasterID</code> dropdown but not in <code>ChildID</code>. Also the value 5 from <code>ID</code> column is mapped to <code>ChildID</code> and saved, where this value should not appear in <code>MasterID</code> and <code>ChildID</code> dropdowns. Once any value is selected as the <code>ChildID and saved, then it shouldn't get displayed in</code>MasterID<code>or in</code>ChildID` dropdowns.</p>
  
  <p>Final Output should be like this.</p>
  
  <p><strong>Table 2:</strong>   </p>
  
  <pre><code>MasterID    ChildID
     1           5
     2           3
     2           6
     4           7
     4           8
     9           0
  </code></pre>
  
  <p>Can anyone help me or suggest how I can achieve this for asp.net web application.</p>