Match the value In the DropDownlist through SQL IN ASP.NET?

Question

Hi Friends,
    I made a table in the SQL DATABASE in which two values are displayed one is the value and other is the code of that particular value. Now In Asp.net all these values are displayed in the dropdownlist. I want when I click on any value in the dropdownList the corresponding code of that clicked value will be fetch from the database and Display that code in the label. How can this possible? Please help me out.