Today I had to update a system with a new kind of device. A device setup is a bit complex and when they start they look into a configuration file and try to transform/cast some “System.Configuration.ConfigurationManager.ConnectionStrings” into their corresponding Enum value in the system.
My Enum looks like:
public enum DeviceType
{
[Description("Apple IPod")]
IPOD = 1,
[Description("Apple iPad")]
APPLE_IPAD,
[Description("Google Glass")]
GGlass,
[Description("Surface")]
MS_SURFACE,
[Description("MS Surface PRO")]
MS_SURFACE_PRO,
[Description("Unknow")]
UNKNOW = 1000
}
After the addition of the “Google Glass” device … I quickly discovered that in several place I have to add an additional else in an already too long if-else sequence to handle the conversion of the string in an Enum value.
if(MyDeviceType == Device.IPOD.ToString())
MyDeviceType = DeviceType.IPOD;
else if(MyDeviceType == Device.APPLE_IPAD.ToString())
MyDeviceType = DeviceType.APPLE_IPAD;
etc...
If think it looks like that just because too many developers doesn’t master the language they use and first I would say that from my point of view I’m not a master but just a developer aware some useful functionalities of C# and one I like is the template and how you can explore the types/values and check if they have attribute.
So to simply, improve the code and add a bit of flexibility in the configuration string we use I decided to add an “Helpers” method in that system to definitely solve that issue.
public static class Helpers
{
public static T GetValueFromDescription<T>(string description)
{
var type = typeof(T);
if (!type.IsEnum) throw new InvalidOperationException();
foreach (var field in type.GetFields())
{
if (field.Name == description)
return (T)field.GetValue(null);
var attribute = Attribute.GetCustomAttribute(field,
typeof(DescriptionAttribute)) as DescriptionAttribute;
if (attribute != null)
{
if (attribute.Description == description)
return (T)field.GetValue(null);
}
}
throw new ArgumentException("Not found.", "description");
}
}
As you can see, it’s really easy to read. If T is an Enum, we iterate over all field in the Enum. If the string match with a filed name (i.e “IPOD”, “APPLE_IPAD”) it’s OK, we return the field value. If it doesn’t match we look for a Description Attribute. Those attribute are really useful to provide a human readable description for Enum value, class data member, etc… So here if the config string match with a config attribute it’s also OK and due to that “IPOD” and “Apple IPod” return the same Enum value (Flexibility !).
And now if I replace all the existing if-else sequence by something like:
type = DeviceType.UNKNOW;
try
{
type = ExtensionMethods.GetValueFromDescription<DeviceType>(configuration_string);
}
catch (Exception ) //silently ...
{
type = DeviceType.UNKNOW;
}
It looks better from my point of view and next time we will a new device type all the mapping code is ready, no update to do !
The only thing I really regret is that all those cool device are only here for the example and I don’t have or work with them …. Snif Snif !
As one of my holidays book is “Digital Fortress” from the very well-known 
