I thought it would be easy, but I’m not being able to find how to do it. I found how to do it with a checkbox (http://msdn.microsoft.com/en-us/library/system.windows.forms.checkbox.appearance.aspx).
But, how could do it with the checkboxlist control?
As Steve B suggested, a nice way is to use jQuery. I put a checkbox inside a asp:Repeater control, and I modify the appearance of this checkbox to look like a button. This is the code:
And in the code behind:
I hope it is useful for somebody!
Carlos