Hello everyone I've been trying to put some objects in an ASP.NET list box but its just not working.

I do have an overriden ToString method so I cant understand why this statement wont work. Here's the code that I use:

for (int i = 0; i < fitnessClassList.Count(); i++)
{
    lbDisplayItems.Items.Add(fitnessClassList.getFitnessClass(i));
}

And the errors that I get:

Error   2   Argument 1: cannot convert from 
                    'FitnessClassManager.FitnessClassOpportunity' to 
                    'System.Web.UI.WebControls.ListItem'    

Error   1   The best overloaded method match for 
                    'System.Web.UI.WebControls.ListItemCollection.Add(System.Web.UI.WebControls.ListItem)' 
                    has some invalid arguments