Underlying numeric values in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are underlying numeric values in C# enums?

Underlying numeric values are the integer values automatically or explicitly assigned to each enum member. By default, they start at 0 and increase by 1 for each member.

beginner

How can you specify a custom underlying numeric value for an enum member in C#?

You assign a value directly to the enum member, for example: enum Days { Sunday = 1, Monday = 2 }.

beginner

What is the default underlying type of an enum in C#?

The default underlying type of an enum in C# is int.

intermediate

Can you change the underlying type of an enum in C#? If yes, how?

Yes, you can specify a different integral type like byte, short, long by declaring it after the enum name, e.g., enum Colors : byte { Red, Green }.

beginner

How do you get the underlying numeric value of an enum member in C#?

You can cast the enum member to its underlying type, for example: int value = (int)Days.Monday;.

What is the default underlying numeric value of the first enum member if not specified?

A 0

B 1

C -1

D Depends on the enum

By default, the first enum member has the underlying value 0.

How do you specify an enum with an underlying type of byte?

A enum Colors(byte) { Red, Green }

B enum Colors : byte { Red, Green }

C enum Colors { Red = byte, Green = byte }

D enum Colors { byte Red, byte Green }

The syntax to specify the underlying type is enum Name : type { ... }.

What happens if you assign the same numeric value to two enum members?

A It causes a compile error

B The second member gets incremented automatically

C Both members share the same underlying value

D The enum becomes invalid

Enum members can share the same underlying value without error.

How do you retrieve the numeric value of an enum member in C#?

A Use a cast like (int)EnumMember

B Use Enum.GetValue() method

C Use Enum.ToString()

D Use Enum.Parse()

Casting the enum member to its underlying type returns its numeric value.

Which of these is NOT a valid underlying type for an enum in C#?

A int

B byte

C long

D string

Enums can only have integral underlying types, not string.

Explain what underlying numeric values are in C# enums and how they are assigned.

Think about how enum members get their numbers.

Describe how to change the underlying type of an enum and why you might want to do that.

Look at the enum declaration syntax.