A ClassBreaksRenderer should have 2 or more ClassBreakInfo Classes (meaning classification or grouping) to delineate the different symbology and class break information. Otherwise use a SimpleRenderer if just one type of symbology needs to be rendered.

When a ClassBreaksRenderer object is created the ObservableCollection (Of ClassBreakInfo) object is also created that is accessable from the ClassBreaksRenderer.Classes Property. Although the Classes Property is ReadOnly, meaning you can only get the ObservableCollection (Of ClassBreakInfo) object, you can use its Members to like: Add, Clear, Remove, etc. to define how the ClassBreaksRenderer behaves.

To see a full example of how to set and use the Classes Property in a ClassBreaksRenderer review the ClassBreaksRenderer Class documentation.