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Abstract class

Abstract methods for abstracting

Abstract methods cannot have method bodies

Abstract methods cannot be instantiated because there are abstract members, and abstract members cannot have the method body

Subclasses must override the abstract method of the parent class

abstract method of parent class cannot be called from the base keyword in a subclass

The abstract method is what the light says and does, but defines the behavior, but the specific implementation is given to the subclass

Abstract classes can have non-abstract members, in order to inherit to subclasses

You can have virtual methods in an abstract class

Subclasses must override the parent class's methods, and the parent class does not have to be instantiated , using abstract classes

Abstract classes are inherited for polymorphic

Abstract members cannot be private

An interface is a special abstract class.

Use interface to define 1 interfaces

The interface indicates that it has some kind of capability

Members that can be defined in an interface

Interface cannot be serialized

The member in the interface is abstract by default

The interface can only define properties, methods, indexers, events

Abstract members cannot have access modifiers, default is public

To implement an interface class, you must implement all the members of the interface

Class does not require the override keyword When implementing members of an interface

When implementing a member, you must ensure that the signature is consistent

Interface is 1 purely for the purpose of canonical implementation class

Abstract class : You can find the parent class, and you want to inherit from the parent class to some member families of the subclass

Interface : Multiple classes have the same method, but cannot find the parent class, you can define the method in the interface, let these classes to implement

1 classes can inherit only 1 parent classes, but can implement multiple interfaces, the parent class to write in the first position, to some extent, solve the problem of the single root of the class,

Interfaces themselves can inherit interfaces and support multiple inheritance

The members of the interface can be implemented as abstract or virtual methods, allowing subclasses of the implementation class to implement

Avoid defining multi-function interfaces to prevent contamination of the interface

Boxing : Converting a value type to a reference type

Unboxing : Converting a reference type to a value type

String Special Reference types

String can be seen as a 1 - character Array

Length indicates the number of characters in a string

A string object cannot be modified once the object is created

When you create 1 string objects, you first go to the string detention pool and look for objects with the same string content.

If there is a direct argument to the object, if there is no new object in the creation

String Common methods :

The Length property represents the number of characters

Empty represents 1 empty strings "" emphasizes not referring to null

Compare comparing the size of 2 strings

Concat the connection string and makes up 1 new strings

Contains () Determines whether the specified string contains the specified string

EndsWith () Determines whether the specified string ends with the specified string

StartsWith () Determines whether the specified string starts with the specified string

Equals (); Determines whether the contents of the specified string are the same as the specified string

Format () formatted string

IndexOf () finds the index of the specified character or string in the string, if not returned-1

LastIndexOf () from the end of the string to the front, the first occurrence of the index of the string

IsNullOrEmpty () Determines whether the specified string is not a null value or a string. Enpty

Remove if only one int type is passed, the previous is preserved, and the subsequent

Replace replacement string

Split returns an array with the specified character split string

Substring Cutting strings

ToCharArray () Converts a string to a character input group

ToLower () Converts a string to lowercase

ToUpper () Converts a string to uppercase

Trim () Remove the spaces before and after the string

When we need a lot of string concatenation we can use the stringbulider class

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