It just hit me that your best answer is probably to just keep track of whether a default case has been defined:
class Switch
{
private Dictionary<Type, Action<object>> _dict;
private Action<object> defaultCase;
public Switch(params KeyValuePair<Type, Action<object>>[] cases)
{
_dict = new Dictionary<Type, Action<object>>(cases.Length);
foreach (var entry in cases)
if (entry.Key == null)
defaultCase = entry.Value;
else
_dict.Add(entry.Key, entry.Value);
}
public void Execute(object obj)
{
var type = obj.GetType();
if (_dict.ContainsKey(type))
_dict[type](obj);
else if (defaultCase != null)
defaultCase(obj);
}
...
The whole rest of your class would remain untouched.
