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Advanced application of C ＃ language
2022-07-05 19:04:00 【Youth programming competition communication】
C# Advanced application of language
1、 attribute
example 1： Introduction of attribute concept （ problem ）
public class Animal
{
public int Age;
public double Weight;
public bool Sex;
public Animal(int age, double weight, bool sex)
{
Age = age;
Weight = weight;
Sex = sex;
}
public void Eat()
{
Console.WriteLine("Animal Eat.");
}
public void Sleep()
{
Console.WriteLine("Animal Sleep.");
}
public override string ToString()
{
return string.Format("Animal Age:{0}, Weight:{1}, Sex:{2}", Age, Weight, Sex);
}
}
class Program
{
static void Main(string[] args)
{
Animal al = new Animal(1, 1.2, false);
Console.WriteLine("Animal Age:{0}, Weight:{1}, Sex:{2}", al.Age, al.Weight, al.Sex);
al.Age = -1;
al.Weight = -0.5;
Console.WriteLine(al);
}
}
example 2： Problem solving （Java Language solution to this problem ）
public class Animal
{
private int _age;
private double _weight;
private readonly bool _sex;
public int GetAge()
{
return _age;
}
public void SetAge(int value)
{
_age = (value > 0) ? value : 0;
}
public double GetWeight()
{
return _weight;
}
public void SetWeight(double value)
{
_weight = (value > 0) ? value : 0;
}
public bool GetSex()
{
return _sex;
}
public Animal(int age, double weight, bool sex)
{
_age = (age > 0) ? age : 0;
_weight = (weight > 0) ? weight : 0;
_sex = sex;
}
public void Eat()
{
Console.WriteLine("Animal Eat.");
}
public void Sleep()
{
Console.WriteLine("Animal Sleep.");
}
public override string ToString()
{
return string.Format("Animal Age:{0}, Weight:{1}, Sex:{2}", _age, _weight, _sex);
}
}
class Program
{
static void Main(string[] args)
{
Animal al = new Animal(1, 1.2, false);
Console.WriteLine("Animal Age:{0},Weight:{1},Sex:{2}", al.GetAge(), al.GetWeight(), al.GetSex());
al.SetAge(-1);
al.SetWeight(-0.5);
Console.WriteLine(al);
}
}
example 3： The proposal of attributes
public class Animal
{
private int _age;
private double _weight;
private readonly bool _sex;
public int Age
{
get {
return _age; }
set {
_age = (value > 0) ? value : 0; }
}
public double Weight
{
get {
return _weight; }
set {
_weight = (value > 0) ? value : 0; }
}
public bool Sex
{
get {
return _sex; }
}
public Animal(int age, double weight, bool sex)
{
_age = (age > 0) ? age : 0;
_weight = (weight > 0) ? weight : 0;
_sex = sex;
}
public void Eat()
{
Console.WriteLine("Animal Eat.");
}
public void Sleep()
{
Console.WriteLine("Animal Sleep.");
}
public override string ToString()
{
return string.Format("Animal Age:{0}, Weight:{1}, Sex:{2}", Age, Weight, Sex);
}
}
class Program
{
static void Main(string[] args)
{
Animal al = new Animal(1, 1.2, false);
Console.WriteLine("Animal Age:{0}, Weight:{1}, Sex:{2}", al.Age, al.Weight, al.Sex);
al.Age = -1;
al.Weight = -0.5;
Console.WriteLine(al);
}
}
explain ：C# In a statement data You can define set、get Method .
get： Define read operations .set： Define assignment operation ,valueRepresents the parameter value passed in .
example 4： Simplification of attributes
public class Animal
{
private int _age;
private double _weight;
public int Age
{
get {
return _age; }
set {
_age = (value > 0) ? value : 0; }
}
public double Weight
{
get {
return _weight; }
set {
_weight = (value > 0) ? value : 0; }
}
public bool Sex {
get; private set; }
public Animal(int age, double weight, bool sex)
{
_age = (age > 0) ? age : 0;
_weight = (weight > 0) ? weight : 0;
Sex = sex;
}
public void Eat()
{
Console.WriteLine("Animal Eat.");
}
public void Sleep()
{
Console.WriteLine("Animal Sleep.");
}
public override string ToString()
{
return string.Format("Animal Age:{0},Weight:{1},Sex:{2}", Age, Weight, Sex);
}
}
class Program
{
static void Main(string[] args)
{
Animal al = new Animal(1, 1.2, false);
Console.WriteLine("Animal Age:{0}, Weight:{1}, Sex:{2}", al.Age, al.Weight, al.Sex);
al.Age = -1;
al.Weight = -0.5;
Console.WriteLine(al);
}
}
explain ： Attributes can be seen as an added layer of isolation for private data parts .
2、 Indexer
2.1 Definition
Is a special attribute in a collection class , It can make the elements in the collection class access like array elements .
2.2 Grammatical structure
public Element type this[int index]
{
get {
... }
set {
... }
}
public Element type this[string name]
{
get {
... }
set {
... }
}
example 5： Use indexer to realize the collection class StudentSet Medium element Student The interview of .
public class Student
{
private string _name;
public string Name
{
get {
return _name; }
set
{
_name = string.IsNullOrEmpty(value)
? "NULL"
: value;
}
}
public long ID {
get; set; }
public Student(long id, string name)
{
ID = id;
_name = name;
}
public override string ToString()
{
return string.Format("ID:{0},Name:{1}", ID, Name);
}
}
public class StudentSet
{
private readonly int _maxCount = 500;
private readonly Student[] _stus;
public int Count
{
get; private set;
}
public StudentSet()
{
Count = 0;
_stus = new Student[_maxCount];
}
public void Add(Student stu)
{
if (stu == null)
throw new ArgumentNullException();
if (Count == _maxCount)
throw new IndexOutOfRangeException();
_stus[Count] = stu;
Count++;
}
public Student this[int index]
{
get
{
if (index < 0 || index > Count - 1)
throw new IndexOutOfRangeException();
return _stus[index];
}
set
{
if (index < 0 || index > Count - 1)
throw new IndexOutOfRangeException();
if (value == null)
throw new ArgumentNullException();
_stus[index] = value;
}
}
}
class Program
{
static void Main(string[] args)
{
StudentSet stuSet = new StudentSet();
stuSet.Add(new Student(10086, " Zhang San "));
stuSet.Add(new Student(95988, " Li Si "));
stuSet[1].Name = string.Empty;
Console.WriteLine(stuSet.Count);
Console.WriteLine(stuSet[0]);
Console.WriteLine(stuSet[1]);
Console.WriteLine(stuSet[2]);
// Unhandled exception : System.IndexOutOfRangeException: Index out of array bounds .
}
}
3、 Interface
3.1 Concept
- Interface is the blueprint of class design , That is, only the declaration is provided without implementation .
- Interfaces cannot directly instantiate objects （ Same as abstract class ）.
- C# Allow a class to implement multiple interfaces （ Pay attention to the difference between inheritance ）.
- An interface contains a series of methods that are not implemented , And hand over the implementation of these methods to the classes that inherit them .
3.2 Express
example 6： Use according to the class diagram Dog Realization IAnimal Interface
public interface IAnimal
{
int Age {
get; set; }
double Weight {
get; set; }
void Eat();
void Sleep();
}
public class Dog : IAnimal
{
private int _age;
private double _weight;
public int Age
{
get {
return _age; }
set {
_age = (value >= 0) ? value : 0; }
}
public double Weight
{
get {
return _weight; }
set {
_weight = (value >= 0) ? value : 0; }
}
public void Eat()
{
Console.WriteLine("Dog Eat");
}
public void Sleep()
{
Console.WriteLine("Dog Sleep");
}
}
class Program
{
static void Main(string[] args)
{
IAnimal al = new Dog();
al.Age = 1;
al.Weight = 2.5;
Console.WriteLine("Dog:Age={0}, Weight={1}", al.Age, al.Weight);
al.Eat();
al.Sleep();
}
}
example 7： Use the interface to realize “ Feeding system ”
A breeder （Raiser） At present, three kinds of animals need to be raised ： Dog （Dog）、 bird （Bird） And fish （Fish）, The three animals only need to sleep （Sleep） And eating （Eat） that will do . Please design the feeding system , It is required to meet the requirements of software design “ Opening and closing principle ”.
Scheme 1 ：（ It has been given in the abstract class section ）
Option two ：
public interface IAnimal
{
int Age {
get; set; }
double Weight {
get; set; }
void Eat();
void Sleep();
}
public class Bird : IAnimal
{
private int _age;
private double _weight;
public int Age
{
get {
return _age; }
set {
_age = (value >= 0) ? value : 0; }
}
public double Weight
{
get {
return _weight; }
set {
_weight = (value >= 0) ? value : 0; }
}
public void Eat()
{
Console.WriteLine("Bird Eat.");
}
public void Sleep()
{
Console.WriteLine("Bird Sleep.");
}
public void Fly()
{
Console.WriteLine("Bird Fly.");
}
}
public class Dog : IAnimal
{
private int _age;
private double _weight;
public int Age
{
get {
return _age; }
set {
_age = (value >= 0) ? value : 0; }
}
public double Weight
{
get {
return _weight; }
set {
_weight = (value >= 0) ? value : 0; }
}
public void Eat()
{
Console.WriteLine("Dog Eat.");
}
public void Sleep()
{
Console.WriteLine("Dog Sleep.");
}
public void Run()
{
Console.WriteLine("Dog Run.");
}
}
public class Fish : IAnimal
{
private int _age;
private double _weight;
public int Age
{
get {
return _age; }
set {
_age = (value >= 0) ? value : 0; }
}
public double Weight
{
get {
return _weight; }
set {
_weight = (value >= 0) ? value : 0; }
}
public void Eat()
{
Console.WriteLine("Fish Eat.");
}
public void Sleep()
{
Console.WriteLine("Fish Sleep.");
}
public void Swim()
{
Console.WriteLine("Fish Swim.");
}
}
public class Raiser
{
public void Raise(IAnimal al)
{
al.Eat();
al.Sleep();
}
}
class Program
{
static void Main(string[] args)
{
Raiser rsr = new Raiser();
rsr.Raise(new Dog());
rsr.Raise(new Bird());
rsr.Raise(new Fish());
}
}
3.3 Interface （interface） And abstract classes （abstract class）
（1） The same thing ：
- Neither interfaces nor abstract classes can directly instantiate objects .
（2） Difference ：
- Data and operations in abstract classes must have restriction modifiers , The data and operations in the interface cannot have restriction modifiers .
- Abstract classes can have methods with implementations （ Not abstract Method ）, Interfaces can only have method declarations .
- Abstract classes pass in subclasses override Keyword override abstract method , The interface is directly implemented by subclasses .
example 8： A class can implement multiple interfaces , However, you should pay attention to the handling of duplicate methods in multiple interfaces .
Mode one ：
public interface IHighWayWorker
{
void HighWayOperation();
void Build();
}
public interface IRailWayWorker
{
void RailWayOperation();
void Build();
}
public class Worker : IRailWayWorker, IHighWayWorker
{
public void HighWayOperation()
{
Console.WriteLine("HighWayOperation.");
}
public void RailWayOperation()
{
Console.WriteLine("RailWayOperation");
}
public void Build()
{
Console.WriteLine("HighWay,RailWay,Build.");
}
}
class Program
{
static void Main(string[] args)
{
Worker wr = new Worker();
wr.Build(); // HighWay,RailWay,Build.
IHighWayWorker hwr = new Worker();
hwr.Build(); // HighWay,RailWay,Build.
hwr.HighWayOperation(); // HighWayOperation.
IRailWayWorker rwr = new Worker();
rwr.Build(); // HighWay,RailWay,Build.
rwr.RailWayOperation();// RailWayOperation
}
}
Mode two ：
public interface IHighWayWorker
{
void HighWayOperation();
void Build();
}
public interface IRailWayWorker
{
void RailWayOperation();
void Build();
}
public class Worker : IHighWayWorker, IRailWayWorker
{
public void HighWayOperation()
{
Console.WriteLine("HighWayOperation.");
}
public void RailWayOperation()
{
Console.WriteLine("RailWayOperation");
}
void IHighWayWorker.Build()
{
Console.WriteLine("HighWay Build.");
}
void IRailWayWorker.Build()
{
Console.WriteLine("RailWay Build.");
}
// Be careful ：void IHighWayWorker.Build() and void IRailWayWorker.Build()
// No restriction modifier can be added in front .
}
class Program
{
static void Main(string[] args)
{
Worker wr = new Worker();
//wr.Build(); The statement is incorrect
IHighWayWorker hwr = new Worker();
hwr.Build();//HighWay Build.
hwr.HighWayOperation();//HighWayOperation.
IRailWayWorker rwr = new Worker();
rwr.Build();//RailWay Build.
rwr.RailWayOperation();//RailWayOperation
}
}
4、 Generic
example 9： Storage int Collection and operation of data types .
public class IntSet
{
private readonly int _maxSize;
private readonly int[] _set;
public IntSet()
{
_maxSize = 100;
_set = new int[_maxSize];
//...
}
public void Insert(int k, int x)
{
//....
_set[k] = x;
}
public int Locate(int k)
{
//...
return _set[k];
}
}
class Program
{
static void Main(string[] args)
{
IntSet iSet = new IntSet();
iSet.Insert(0, 123);
int i = iSet.Locate(0);
Console.WriteLine(i); // 123
}
}
example 10： Storage string Collection and operation of data types .
public class StringSet
{
private readonly int _maxSize;
private readonly string[] _set;
public StringSet()
{
_maxSize = 100;
_set = new string[_maxSize];
//...
}
public void Insert(int k, string x)
{
//....
_set[k] = x;
}
public string Locate(int k)
{
//...
return _set[k];
}
}
class Program
{
static void Main(string[] args)
{
StringSet strSet = new StringSet();
strSet.Insert(0, "abc");
string j = strSet.Locate(0);
Console.WriteLine(j); // abc
}
}
example 11： utilize object Class stores collections and operations of general data types .
public class GSet
{
private readonly int maxSize;
private readonly object[] _set;
public GSet()
{
maxSize = 100;
_set = new object[maxSize];
//...
}
public void Insert(int k, object x)
{
//....
_set[k] = x;
}
public object Locate(int k)
{
//...
return _set[k];
}
}
class Program
{
static void Main(string[] args)
{
GSet gSet1 = new GSet();
gSet1.Insert(0, 123);
int k1 = (int)gSet1.Locate(0);
Console.WriteLine(k1); // 123
GSet gSet2 = new GSet();
gSet2.Insert(0, "abc");
string k2 = (string)gSet2.Locate(0);
Console.WriteLine(k2); // abc
GSet gSet3 = new GSet();
gSet3.Insert(0, 123);
gSet3.Insert(1, "abc");// At compile time, you can use , Exception at runtime .
int k3 = (int)gSet3.Locate(1); // There is a type safety problem in this way .
Console.WriteLine(k3);
// Unhandled exception : System.InvalidCastException: Invalid conversion specified .
}
}
Generic definition ： I.e. parameterized type .
Replace the parameter type with a specific type at compile time , Type safe classes can be defined without affecting work efficiency .
example 12： Using generics T Store collections and operations of common data types .
public class GSet<T>
{
private readonly int _maxSize;
private readonly T[] _set;
public GSet()
{
_maxSize = 100;
_set = new T[_maxSize];
//...
}
public void Insert(int k, T x)
{
//....
_set[k] = x;
}
public T Locate(int k)
{
//...
return _set[k];
}
}
class Program
{
static void Main(string[] args)
{
GSet<int> gSet1 = new GSet<int>();
gSet1.Insert(0, 123);
int k1 = gSet1.Locate(0);
Console.WriteLine(k1); // 123
GSet<string> gSet2 = new GSet<string>();
gSet2.Insert(0, "abc");
string k2 = gSet2.Locate(0);
Console.WriteLine(k2); // abc
}
}
We put T This is called a type parameter , Of course, we can also deal with T Constraint .
example 13： Is a type parameter T Add constraints , such as T Can only be value type .
public class GSet<T> where T : struct
{
private readonly int _maxSize;
private readonly T[] _set;
public GSet()
{
_maxSize = 100;
_set = new T[_maxSize];
//...
}
public void Insert(int k, T x)
{
//....
_set[k] = x;
}
public T Locate(int k)
{
//...
return _set[k];
}
}
class Program
{
static void Main(string[] args)
{
GSet<int> gSet1 = new GSet<int>();
gSet1.Insert(0, 123);
int k1 = gSet1.Locate(0);
Console.WriteLine(k1); // 123
// GSet<string> gSet2 = new GSet<string>(); // Compile error
// error CS0453 type “string” Must be cannot be null The type of value ,
// Can be used as a generic type or method “GSet < T >” Parameters in “T”
}
}
For generic constraints, see the following diagram ：
5、 The relationship between classes
public class Oxygen
{
//...
}
public class Water
{
//...
}
public abstract class Animal
{
public int Age;
public double Weight;
public abstract void Eat();
public abstract void Sleep();
public abstract void Breed();
public abstract void Metabolism(Oxygen o2, Water water);
}
public class Bird : Animal
{
public string Feather;
public void Fly()
{
//...
}
public void Egg()
{
//...
}
public override void Eat()
{
//...
}
public override void Sleep()
{
//...
}
public override void Breed()
{
//...
}
public override void Metabolism(Oxygen o2, Water water)
{
//...
}
}
public class Penguin : Bird
{
//...
}
public class Goose : Bird
{
//...
}
public class Duck : Bird
{
//...
}
public class Climate
{
//...
}
public class Penguin : Bird
{
private Climate _climate;
//...
}
public interface ILanguage
{
void Speak();
}
public class DonaldDuck : Duck, ILanguage
{
public void Speak()
{
//...
}
//...
}
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