title: How to validate combo box values in c#
body: <p><img src="https://i.stack.imgur.com/0Bzc8.png" alt="enter image description here">I have 6 combo boxes in c# form that all fill from database from same column. i-e for making student result combo boxes fill subject names. now I want is how to delete Subject name from 2nd combo box if the Subject is already selected in the previous combo box.and i use combo box property to fill each combo box from database. </p>