How to get next (or previous) enum value in C#

Question

I have an enum which is defined like this:

public enum eRat { A = 0, B=3, C=5, D=8 };

So given value eRat.B, I want to get the

Answer 1

From comments I had many question like: "Why would you ever want to use enum in this way." Since so many of you asked, let me give you my use case and see if you agree then:

I have a fixed array of items int[n]. Depending on the situation I want to enumerate through this array differently. So i defined:

int[] Arr= {1,2,34,5,6,78,9,90,30};
enum eRat1 { A = 0, B=3, C=5, D=8 }; 
enum eRat2 { A, AA,AAA,B,BB,C,C,CC,D }; 

void walk(Type enumType) 
{ 
   foreach (Type t in Enum.GetValues(enumType)) 
   { 
      write(t.ToString() + " = " + Arr[(int)t)]; 
   }
} 

and call walk(typeof(eRAt1)) or walk(typeof(eRAt2))

then i get required output

1) walk(typeof(eRAt1))

A = 1
B = 5
C = 78
D = 30

2) walk(typeof(eRAt2))

A = 1
AA = 2
AAA = 34
B = 5
BB = 6
C = 78
CC = 90
D = 30

This is very simplified. But i hope, this explains. There are some other advantages to this, as having enum.toString(). So basically i use enums as indexers.

So using the solution I can do something like this now.

In sequence eRat1 next value to B is C, but in eRat2 it is BB. So depending on which sequence I am interested in, I can do e.next and depending on enumType I will either get C or BB. How would one achieve that with dictionaries?

I think this a rather elegant use of enums.