title: How to refresh dropdownlist in C#?
body: <p>I would like my drop down list to be auto refreshed when the user chooses a particular option.</p>
  
  <p>For example given there are 2 drop down lists, 1 for Model and the other for Tester.</p>
  
  <p>My table of data looks something like this but with 100+ data:</p>
  
  <p><img src="https://i.stack.imgur.com/xcJ6c.png" alt="enter image description here"></p>
  
  <p>Here are 2 examples of how I want my drop down list to be displayed.
  <img src="https://i.stack.imgur.com/1rtsH.png" alt="enter image description here">
  <img src="https://i.stack.imgur.com/d2xfY.png" alt="enter image description here"></p>
  
  <p>(PS:I intend on writing simple codes for this as I am an amateur programmer so the less complex the solution is, the better.)</p>
  
  <p>Thanks.</p>
  
  <p><strong>Detailed Explanation</strong></p>
  
  <p><em>start</em></p>
  
  <p>When the user selects G123 from the model drop down list, the tester drop down list should only display those testers who have tested G123 and not the entire list of testers. Similarly, when the user selects a particular tester, only the models tested by that tester should be displayed and not the entire list of models.</p>
  
  <p>My final result should have "All" as the first drop down list option included in both drop down list as well. (All models / All Testers). This "All" selection should only select all the models/testers that that particular tester/model has done and not the entire list of Model/Testers.</p>
  
  <p><em>end</em></p>