类型转换 #

byte b = 10;
short s = b;
int i = s;
long l = i;
float f = l;
double d = f;

byte → short → int → long → float → double
  ↓
sbyte
  ↓
short → int → long → float → double

char → int → long → float → double

int intValue = 100;
long longValue = intValue;

float floatValue = 3.14f;
double doubleValue = floatValue;

char charValue = 'A';
int charToInt = charValue;

int number = 10;
int? nullableNumber = number;

double d = 123.456;
int i = (int)d;

long l = 1000L;
int j = (int)l;

float f = 3.99f;
int k = (int)f;

double d = 123.999;
int i = (int)d;

long bigNumber = 3000000000L;
int overflow = (int)bigNumber;

checked
{
    int max = int.MaxValue;
    int overflow = max + 1;
}

int result = checked((int)bigNumber);

unchecked
{
    int max = int.MaxValue;
    int overflow = max + 1;
}

int number = int.Parse("123");
double price = double.Parse("3.14");
bool flag = bool.Parse("true");
DateTime date = DateTime.Parse("2024-01-01");

try
{
    int number = int.Parse("abc");
}
catch (FormatException ex)
{
    Console.WriteLine($"格式错误：{ex.Message}");
}

int number = int.Parse("FF", System.Globalization.NumberStyles.HexNumber);
double value = double.Parse("1,234.56", CultureInfo.InvariantCulture);
DateTime date = DateTime.ParseExact("2024-01-01", "yyyy-MM-dd", null);

string input = "123";
if (int.TryParse(input, out int number))
{
    Console.WriteLine($"转换成功：{number}");
}
else
{
    Console.WriteLine("转换失败");
}

bool intSuccess = int.TryParse("123", out int intResult);
bool doubleSuccess = double.TryParse("3.14", out double doubleResult);
bool boolSuccess = bool.TryParse("true", out bool boolResult);
bool dateSuccess = DateTime.TryParse("2024-01-01", out DateTime dateResult);

Console.Write("请输入年龄：");
string input = Console.ReadLine();

if (int.TryParse(input, out int age) && age > 0 && age < 150)
{
    Console.WriteLine($"您的年龄是：{age}");
}
else
{
    Console.WriteLine("请输入有效的年龄");
}

int i = Convert.ToInt32("123");
double d = Convert.ToDouble("3.14");
bool b = Convert.ToBoolean("true");
string s = Convert.ToString(123);

int number = 255;

string binary = Convert.ToString(number, 2);
string octal = Convert.ToString(number, 8);
string hex = Convert.ToString(number, 16);

int fromBinary = Convert.ToInt32("11111111", 2);
int fromHex = Convert.ToInt32("FF", 16);

int result1 = Convert.ToInt32("123");
int result2 = int.Parse("123");

int result3 = Convert.ToInt32(null);

int number = 42;
object boxed = number;

object boxed = 42;
int number = (int)boxed;

var list = new ArrayList();
for (int i = 0; i < 1000000; i++)
{
    list.Add(i);
}

var genericList = new List<int>();
for (int i = 0; i < 1000000; i++)
{
    genericList.Add(i);
}

public void ProcessValue(object value)
{
    int number = (int)value;
}

public void ProcessValue<T>(T value)
{
}

object obj = "Hello";
string str = obj as string;

if (str != null)
{
    Console.WriteLine(str);
}

object obj = "Hello";

if (obj is string str)
{
    Console.WriteLine(str.Length);
}

if (obj is int number)
{
    Console.WriteLine(number);
}

object value = 42;

string result = value switch
{
    int i => $"整数：{i}",
    double d => $"浮点数：{d}",
    string s => $"字符串：{s}",
    null => "null",
    _ => "未知类型"
};

public class Celsius
{
    public double Degrees { get; }
    
    public Celsius(double degrees)
    {
        Degrees = degrees;
    }
    
    public static implicit operator Fahrenheit(Celsius c)
    {
        return new Fahrenheit(c.Degrees * 9 / 5 + 32);
    }
}

public class Fahrenheit
{
    public double Degrees { get; }
    
    public Fahrenheit(double degrees)
    {
        Degrees = degrees;
    }
    
    public static implicit operator Celsius(Fahrenheit f)
    {
        return new Celsius((f.Degrees - 32) * 5 / 9);
    }
}

Celsius c = new Celsius(25);
Fahrenheit f = c;

public class Money
{
    public decimal Amount { get; }
    
    public Money(decimal amount)
    {
        Amount = amount;
    }
    
    public static explicit operator decimal(Money m)
    {
        return m.Amount;
    }
    
    public static explicit operator Money(decimal d)
    {
        return new Money(d);
    }
}

Money money = new Money(100.50m);
decimal amount = (decimal)money;

public int? GetValidNumber(string input)
{
    if (int.TryParse(input, out int result))
    {
        return result;
    }
    return null;
}

public bool TryGetNumber(string input, out int number)
{
    number = 0;
    
    if (string.IsNullOrWhiteSpace(input))
        return false;
    
    return int.TryParse(input, out number);
}

string input = "123.45";

int wrong = int.Parse(input);

if (double.TryParse(input, out double d))
{
    int correct = (int)d;
}