property is obsolete now. As from Q1 2013, RadComboBox introduces the new "RenderMode" property, which accepts three values - Classic, Lightweight and Native.
Unfortunately there is no way to make RadComboBox to look like the standard ASP.NET drop down and act as RadComboBox. This is because RadComboBox is much complicated than the standard drop down. It has templates, filtering, virtual scrolling, load on demand and other features which if you use the combo will be rendered as many div and span elements.
However you could use RadFormDecarator to
make the standard dropdowns and selects to look like RadComboBox.
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