when I download the code of this book,I can't find the example about comboBox in chapter13, So I type the code according the book by myself. But there comes an error, the error discription is:

'TestBoxTest.Form1.Dispose()': cannot override inherited member 'System.ComponentModel.Component.Dispose()' because it is not marked virtual, abstract, or override

Does the writer make a mistake?
Or maybe the reason is in my version of vs.net?

who can tell me the reason , I want your help.