基本数据类型 #

sbyte temperature = -10;
byte age = 25;
short year = 2024;
ushort port = 8080;
int count = 1000000;
uint population = 7_000_000_000;
long ticks = DateTime.Now.Ticks;
ulong fileSize = 1_000_000_000;

int million = 1_000_000;
long bigNumber = 1_000_000_000_000;

float temperature = 36.5f;
double pi = 3.14159265359;
decimal price = 99.99m;
decimal balance = 1_000_000.50m;

float f = 0.1f + 0.2f;
double d = 0.1 + 0.2;
decimal m = 0.1m + 0.2m;

Console.WriteLine(f);
Console.WriteLine(d);
Console.WriteLine(m);

char letter = 'A';
char digit = '7';
char symbol = '@';
char chinese = '中';

char newline = '\n';
char tab = '\t';
char unicode = '\u4E2D';

bool isValid = true;
bool isEmpty = false;
bool hasPermission = true;

bool a = true;
bool b = false;

bool and = a && b;
bool or = a || b;
bool not = !a;

string name = "张三";
string greeting = "Hello, World!";
string empty = string.Empty;
string nullStr = null;

string s1 = "Hello";
string s2 = s1;
s2 = "World";

string firstName = "张";
string lastName = "三";

string fullName1 = firstName + lastName;
string fullName2 = string.Concat(firstName, lastName);
string fullName3 = $"{firstName}{lastName}";

object obj1 = 42;
object obj2 = "Hello";
object obj3 = new List<int>();

int number = (int)obj1;
string text = (string)obj2;

dynamic dyn = 42;
Console.WriteLine(dyn);

dyn = "Hello";
Console.WriteLine(dyn);

dyn = new List<int> { 1, 2, 3 };
Console.WriteLine(dyn.Count);

int? nullableInt = null;
double? nullableDouble = 10.5;
bool? nullableBool = null;

if (nullableInt.HasValue)
{
    int value = nullableInt.Value;
}

int defaultValue = nullableInt ?? 0;

string? nullableString = null;
string nonNullableString = "Hello";

nullableString?.ToString();

int? x = null;
int y = x ?? 0;

string? name = null;
string displayName = name ?? "未知用户";

System.Object
├── 值类型 (ValueType)
│   ├── 简单类型
│   │   ├── 整数类型 (sbyte, byte, short, ushort, int, uint, long, ulong)
│   │   ├── 浮点类型 (float, double, decimal)
│   │   ├── 布尔类型 (bool)
│   │   └── 字符类型 (char)
│   ├── 枚举类型 (enum)
│   └── 结构类型 (struct)
│       ├── DateTime
│       ├── TimeSpan
│       ├── Guid
│       └── Tuple
└── 引用类型
    ├── 字符串 (string)
    ├── 数组 (array)
    ├── 类 (class)
    ├── 接口 (interface)
    ├── 委托 (delegate)
    └── 记录 (record)

int a = 10;
Int32 b = 10;

Type intType = typeof(int);
Type stringType = typeof(string);

Console.WriteLine(intType.Name);
Console.WriteLine(intType.FullName);
Console.WriteLine(intType.IsValueType);

int number = 42;
Type type = number.GetType();

Console.WriteLine(type.Name);

object obj = "Hello";

if (obj is string)
{
    Console.WriteLine("是字符串");
}

if (obj is int)
{
    Console.WriteLine("是整数");
}

string s = "";
for (int i = 0; i < 1000; i++)
{
    s += i;
}

var sb = new StringBuilder();
for (int i = 0; i < 1000; i++)
{
    sb.Append(i);
}
string result = sb.ToString();

public class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public decimal Score { get; set; }
    public bool IsPassed => Score >= 60;
    public char Grade => Score switch
    {
        >= 90 => 'A',
        >= 80 => 'B',
        >= 70 => 'C',
        >= 60 => 'D',
        _ => 'F'
    };
}

public class Product
{
    public string Name { get; set; }
    public decimal Price { get; set; }
    public int Quantity { get; set; }
    
    public decimal TotalPrice => Price * Quantity;
    
    public decimal GetDiscountedPrice(decimal discountRate)
    {
        return TotalPrice * (1 - discountRate);
    }
}

var product = new Product
{
    Name = "笔记本电脑",
    Price = 5999.99m,
    Quantity = 2
};

Console.WriteLine($"商品：{product.Name}");
Console.WriteLine($"单价：{product.Price:C}");
Console.WriteLine($"数量：{product.Quantity}");
Console.WriteLine($"总价：{product.TotalPrice:C}");