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C# Enumeration Cheat Sheet

Emumeration in C# is a great technique to use whilst coding - e.g. when dealing with flags in a database you may have lots of different numeric flags, such as "1" for "accepted", "2" for "declined" and so on. Using enumerators you can just use somthing like "Status.Declined" instead of trying to remember what the numbers mean. It certainly beats using static final int all the time!

Overriding Default Values and Underlying Types

By default, all enumerations have an underlying type of int and start at 0.

enum Days { Monday, Tuesday, Wednesday, Thursday, Friday }
Here, the value for Monday is 0, Tuesday is 1 and so on.

We can override the default values really easily - say we wanted to have Monday's value as 1, Tuesday 2, Wednesday 4 and so on, we'd do this:

enum Days { Monday=1, Tuesday=2, Wednesday=4, Thursday=8, Friday=16 }
Of course we might not want to use int as the type, for example we might want to use long so we can store some larger numbers in there for whatever reason.

enum Days : long { Monday=2147483648, Tuesday=2147483649, Wednesday=2147483650, Thursday=2147483651, Friday=2147483652 }

Getting the value of an enum member

To get a value out of an enum member (e.g. if we wanted to know what number Wednesday was) you'll need to cast it back first.

// WednesdayValue = 2147483650 long WednesdayValue = (long) Days.Wednesday;

Textual descriptions for enum members

Sometimes its cool to have a nice, human understandable description for each of your enum members. For the "Days" example I've used above its not really an issue as we can just use the standard .ToString() method.

// Displays "Monday" Console.Write(Days.Monday.ToString());
But what if we had some status flags? Say we had the following enumeration:

enum Status { Waiting=1, Shipped=2 }
Ok thats fine - we can say in our application "Waiting" or "Shipped" using the .ToString() method, but if we want we can give it better descriptions we simply provide a "Description" attribute for each member, then use the function below to return it as a string.

// Ideally, this code would go in some "Utility" class // hence the use of the static keyword. public static String GetEnumDesc(Enum e) { System.Reflection.FieldInfo EnumInfo = e.GetType().GetField(e.ToString()); System.ComponentModel.DescriptionAttribute[] EnumAttributes = (System.ComponentModel.DescriptionAttribute[]) EnumInfo.GetCustomAttributes (typeof(System.ComponentModel.DescriptionAttribute), false); if (EnumAttributes.Length > 0) { return EnumAttributes[0].Description; } return e.ToString(); } enum Status { [Description("Item is waiting for dispatch.")] Waiting=1, [Description("Item has been shipped.")] Shipped=2 } . . . // Displays "Item is waiting for dispatch." Console.Write(GetEnumDesc(Status.Waiting));
So there you go, the enumerator cheat sheet. Please feel free to leave any comments!

Back 29.05.2006.