string s; 
double d; 

switch(param.getValueType()): 
{ 
	case ValueDataType::STRING_TYPE: 
		s = param.getValue<string>(); 
		break; 
	case ValueDataType::DOUBLE_TYPE: 
		d = param.getValue<double>(); 
		break; 
	default: 
		// blah 
		break; 
}