title: How to filter dropdown list values by another dropdown list in ASP.NET, c#
body: <p>I have a simple question about filters.
  I have 4 dropdown lists which filter the data in my web application from MySQL database table.
  The first dropdown list is already selected showing only one project_id but the others drop down lists displays all the possible values from the database - this is what I made so far. </p>
  
  <p>But I want to display only the data values for that particular project selected.</p>
  
  <p>It's ASP.NET 4.0, C# behind and MySQL database used.
  Any help will be appreciated.
  Thanks</p>