C # Day 6-Enumeration

One weekC #_The6Days

Enumeration

1Type

Value Type

LVariables directly contain their own data

LLocal variables are always placed on the stackStackMedium

Reference Type

NVariables indirectly point to their data

NPoint local variable to heapHeapObjects in

EnumerationEnum	Value Type
structure struct	Value Type
class class	reference type
interface interface	reference type
array [] array	reference type
DeleGate DeleGate	reference type

C #Rules, suchInt,DoubleAnd other internal classes, belong to the structure,C #It is called "simple type ".

The biggest difference between a simple type and a custom type is that a simple type has a literal expression while a custom type does not.

Also, the third type is pointer. Pointers can only be used inUnsafeBlock (unsecureCode.

2Enumeration type

The enumerated type is a user-declared value type.

Enum suit

{

Clubs, diamonds, hearts, spades

} // SuitIndicates a deck,4Medium color: plum blossom, square, red heart, black peach

Sealed Class Example

{

Static void main ()

{

...

Suit lead = spades ;//Here Error

...

Suit trumps = suit. Clubs ;//This is correct.

...

}

}

Enumeration declaration:

Where the class declaration can appear

Including name, access permission, internal type, and enumeration members.

The scope of a variable is to define its enumeration.

Suit trumps = clubs ;//This is incorrect.ClubsLimitedSuitAs follows:

Suit trumps = suit. clubs;

3Enumeration considerations

The default enumerated value type isInt

You can select any internal Integer type.

But it cannot be a role type.

Enum suit: int //Internal type:Int, Can be omitted

{

Clubs,

Diamonds,

Heart = 42 ,//The default value of a member is the value of the previous Member.+ 1But you can also assign an initial value by yourself.

Spades ,//The semicolon of the last member is optional.

};//The end of the semicolon is optional.

Internal variables in the enumeration type can be explicitly declared types include:Sbyte, byte, short, ushort, Int, uint, long, ulong.

If no explicit declaration is made, the default type isInt.

The value of a member must be of the same type as that stated in the enumeration statement. Besides, it must be within the range of type.

If no value is assigned to a member, the value is the value of the previous Member.+ 1The default value of the first Member is1.

The enumerated members can be of the same value.

The last enumerated member can end with a comma.

The default access permission for enumeration members isPublic.

4Use Enumeration

The enumerated type is implicitly derived fromSystem. Enum

Namespace System

{

Public abstract class Enum

{

//Static Functions

Public static string [] getnames (type );

...

//Instance functions

Public override string tostring ();

//Constructor

Protected Enum ();

}

}

 

Suit trumps = suit. clubs;

String [] names = system. enum. getnames (trumps. GetType ());

...

Console. Write (Names [0]); // clubs

Console. Write (trumps); // clubs

Console. Write ("{0}", trumps); // clubs

Console. Write (trumps. tostring (); // clubs

Console. Write (suit) 24); // 24

 

System. EnumYesSystemAn abstract class of the namespace. It implements a series of interfaces:

Public abstract class Enum: icomparable, iformattable, iconvertible

{...}

Enumeration is implicitly derived fromSystem. Enum

System. EnumIt can only be used as an implicit base class of an enumeration type.

Cannot explicitly ExtractSystem. EnumDerive your own class.

Cannot createSystem. EnumClass.

5Enumeration Operator

Enumerated variables are treated as integer variables.

However, in most cases, the shift operator cannot be used.

6Enumeration Conversion

Implicit conversion

L0Can be converted to anyEnumType

LNever throw an error

Explicit Conversion

LSlaveEnumToEnumInternal type conversion

LSlaveEnumConvert to numeric type (includingChar)

LFrom numeric type (includingChar)Enum

LNever throw an error

0Can be converted to anyEnumType.EnumType included?0.