private static Type GetLetterHandlerTypeFromDirectRoute(AddressData addressData)
{
Contract.Assert(addressData != null);
var matchingAddressDatas = addressData.GetDirectAddressMatches();
List <Type> letterHandlerTypes = new List <Type>();
foreach (var directAddressData in matchingAddressDatas)
{
if (directAddressData != null)
{
Type letterHandlerType = directAddressData.GetTargetLetterHandlerType();
if (letterHandlerType == null)
{
// We don't expect this to happen, but it could happen if some code messes with the
// address data tokens and removes the key we're looking for.
throw new InvalidOperationException("Missing Letter Handler Type");
}
if (!letterHandlerTypes.Contains(letterHandlerType))
{
letterHandlerTypes.Add(letterHandlerType);
}
}
}
// We only want to handle the case where all matched direct addresses refer to the same letter handler.
// Handling the multiple-letter handlers case would put attribute routing down a totally different
// path than traditional addressing.
if (letterHandlerTypes.Count == 0)
{
return(null);
}
else if (letterHandlerTypes.Count == 1)
{
return(letterHandlerTypes[0]);
}
else
{
throw CreateDirectAddressAmbiguousLetterHandlerException(letterHandlerTypes);
}
}
