C#

public partial class MyClass1
{
    public void MyMethod1()
    {
        // implementation
    }
}

public partial class MyClass1
{
    public void MyMethod2()
    {
        // implementation
    }
}

class Node<T, V>
    where T : Stack, IComparable, new(), class
    where V : Stack, struct
{...}

// Method that takes an iterable input (possibly an array)
// and returns all even numbers.
public static IEnumerable<int> GetEven(IEnumerable<int> numbers)
{
    foreach (int i in numbers)
    {
        if (i % 2 == 0) yield return i;
    }
}

delegate void NumberChanger(int n);
 
NumberChanger nc = delegate(int x)
{
    Console.WriteLine("Anonymous Method: {0}", x);
};



public void Foo(object parameter)
{
    // ...

    ThreadPool.QueueUserWorkItem(delegate
    {
        // anonymous delegates have full access to local variables of the enclosing method
        if(parameter == ...)
        { 
            // ... 
        }

        // ...
    });
}

string status = string.Empty;

public string Status
{
    get { return status; }             // anyone can get value of this property,
    protected set { status = value; }  // but only derived classes can change it
}

int? i = null;
object o = i;
if(o == null)
    Console.WriteLine("Correct behaviour - runtime version from September 2005 or later");
else
    Console.WriteLine("Incorrect behaviour - pre-release runtime (from before September 2005)");

object nullObj = null; 
object obj = new Object(); 
return nullObj ?? obj; // returns obj

int? i = null;
int j = i ?? 0; // Unless i is null, initialize j to i. Else (if i is null), initialize j to 0.

Customer c = new Customer();
c.Name = "James";

Customer c = new Customer() { Name = "James" };

MyList list = new MyList();
list.Add(1);
list.Add(2);

MyList list = new MyList { 1, 2 };

var x = new { Name = "James" };

var x = new Dictionary<string, List<float>>();

Dictionary<string, List<float>> x = new Dictionary<string, List<float>>();

listOfFoo.Where(
    delegate(Foo x)
    {
        return x.Size > 10; 
    }
)

listOfFoo.Where(x => x.Size > 10);

public string Name
{
    get; 
    set; 
}

public static class IntExtensions
{
    public static void PrintPlusOne(this int x) 
    {
        Console.WriteLine(x + 1);
    }
}
 
int foo = 0;
foo.PrintPlusOne();

partial class C
{
    static partial void M(int i); // defining declaration
}
partial class C
{
    static partial void M(int i)
    {
        dosomething();
    }
}

dynamic calc = GetCalculator();
int sum = calc.Add(10, 20);

public StreamReader OpenFile(string path, int bufferSize = 1024)
{ ... }

OpenFile(bufferSize: 4096, path: "foo.txt");

static void Main(string[] args)
{
    Word.Application wordApplication = new Word.Application() { Visible = true };
    wordApplication.Documents.Open(@"C:\plant.docx", ReadOnly: true);
}

excelObj.Cells[5, 5].Value = "This is sample text";

public interface IComparer<in T>  
{  
    int Compare(T left, T right);  
}

public interface IEnumerable<out T> : IEnumerable
{
    IEnumerator<T> GetEnumerator();
}

using System;

public class Person
{
   public Person(string firstName, string lastName)
   {
      fname = firstName;
      lname = lastName;
   }

   private string fname;
   private string lname;

   public override string ToString() => $"{fname} {lname}".Trim(); //返回值类型string
   public void DisplayName() => Console.WriteLine(ToString()); //返回值类型void
   public string Name => $"{fname} {lname}".Trim();//只读属性
}

using System;
public class Location
{
   private string locationName;

   public Location(string name) => Name = name; //构造函数

   public string Name
   {
      get => locationName;   //get属性
      set => locationName = value;  //set属性
   }

   public override string ToString() => GetType().Name;

   ~Location() => Console.WriteLine($"The {ToString()} finalizer is executing."); //析构函数

   private string[] types = { "Baseball", "Basketball", "Football",
                              "Hockey", "Soccer", "Tennis",
                              "Volleyball" };

   public string this[int i] 
   {
      get => types[i];            //索引器
      set => types[i] = value;
   }
}

public class Student
{
	public Student()
    {
	}
	
	public Student(string studentName,string studentID)
	{
		StudentName = studentName;
		StudentID = studentID;
	}
	
	public string StudentName { get; init; } = "Default Name";
	public string StudentID { get; init; } = "00000000";
}

Student DemoStudent = new Student();
DemoStudent.StudentName = "Test Name";

Student DemoStudent = new Student() //物件初始化運算式
{
    StudentName = "Test Name";
    StudentID = "0001"
};

Student DemoStudent = new Student("Test Name","0001"); //藉由類型的建構式初始化StudentName以及StudentID。

using System;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
        }
    }
}

using System;

Console.WriteLine("Hello World!");
//或者简化为一行语句：
System.Console.WriteLine("Hello World!");

public class InitDemo
{
    public string Start { get; init; }
    public string Stop { get; init; }
}
 
// initDemo.Start = "Now"; // Error
// initDemo.End = "Tomorrow"; // Error
 
var initDemo = new InitDemo
{
    Start = "Now",
    Stop = "Tomorrow"
};

unsafe class FunctionPointer {
 static int GetLength(string s) => s.Length;
 delegate*<string, int> functionPointer = &GetLength;
}
 
public void Test() {
 Console.WriteLine(functionPointer("test")); // 4;
}

[System.Runtime.CompilerServices.SkipLocalsInit]
static unsafe void DemoLocalsInit() {
 int x;
 // 注意， x 没有初始化， 输出结果不确定；
 Console.WriteLine(*&x);
}

Point p = new(1, 1);
Dictionary<string, int> dict = new();
 
Point[] points = { new(1, 1), new (2, 2), new (3, 3) };
var list = new List<Point> { new(1, 1), new(2, 2), new(3, 3)};

using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
namespace CoreApp2
{  
    class Program
    {
        static void Main(string[] args)
        {
            [Conditional("DEBUG")]
            static void DoSomething([NotNull] string test)
            {
                System.Console.WriteLine("Do it!");
            }
            DoSomething("Doing!");
        }
   }
}

using System.Collections.Generic;
using System.Collections.ObjectModel;
namespace CoreApp2
{
    public static class Extensions
    {
        public static IEnumerator<T> GetEnumerator<T>(this IEnumerator<T> enumerator) => enumerator;
    }

    class Program
    {
        static void Main(string[] args)
        {
            IEnumerator<string> enumerator = new Collection<string> {"A", "B", "C"}.GetEnumerator();
            foreach (var item in enumerator)
            {
                Console.WriteLine(item);
            }
        }
    }
}

object obj = new int();
var type = obj switch
{
    string => "string",
    int => "int",
    _ => "obj"
};
Console.WriteLine(type); // int

class Person
{ 
    public string name; 
    public int age; 
    public Person(string a, int b) { name = a;age = b; }
    public void Deconstruct(out string a,out int b){a = name;b = age; }
}

class Program
{        
    static void Main(string[] args)
    {
        var person1 = new Person("Alice", 40);
        var inRange = person1 switch
        {
            (_, < 18) => "less than 18",
            (_, > 18) => "greater than 18",
            (_, 18) => "18 years old!"
        };
        Console.WriteLine(inRange); // greater than 18
    }
}

// And pattern
var person1 = new Person("Alice", 40);
var ageInRange = person1 switch
{
    (_, < 18) => "less than 18",
    ("Zhang Zhimin", _) and (_, >= 18) => "Alice is greater than 18"
};
Console.WriteLine(ageInRange); // Alice is greater than 18

// Or pattern
var person1 = new Person("Alice", 40);
var ageInRange = person1 switch
{
    (_, < 18) => "less than 18",
    (_, 18) or (_, > 18) => "18 or greater"
};
Console.WriteLine(ageInRange); // 18 or greater

// Not pattern
var person1 = new Person("Alice", 40);
var meOrNot = person1 switch
{
    not ("Alice", 40) => "Not me!",
    _ => "Me :-)"
};
Console.WriteLine(meOrNot); // Me :-)

// Parenthesized patterns
var is10 = new IsNumber(true, 10);
var n10 = is10 switch
{
    ((_, > 1 and < 5) and (_, > 5 and < 9)) or (_, 10) => "10",
    _ => "not 10"
};
Console.WriteLine(n10); // 10

using System;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
        }
    }
}