title: Populate dropdown from two tables with differentiation between them
body: <p>I am populating a combobox in C# &amp; SQL.I have two tables to get data from them.</p>
  
  <pre><code>Table1
  
  Id   CategoryName
   1    Salary
   2    Utility
   3    Other
  
  Table2
  
  Id   SubCategoryName   CatId
  1     XYZ Salary         1
  2     YY Salary          1
  3      Car Exp           3
  </code></pre>
  
  <p>Now i want to show them all in a dropdown so that User select any of them and then i will save its Id.</p>
  
  <p>How i will Know that selected Id is from <code>Table1</code> OR <code>Table2</code> ? </p>