.NET
NET is a developer platform with tools and libraries for building any type of app, including web, mobile, desktop, games, IoT, cloud, and microservices.

async Task GetAllPosts()
{
    List<Posts> posts = await GetPosts().ConfigureAwait(false);

    foreach (var post in posts)
        Console.WriteLine(post.Name);
}

// thread 1: initializes the post variable
// thread 1: encounters await, spawns new thread
// thread 2: assigns a new thread to be executed after the current one finishes
// thread 2: finishes to GetPosts(), calls thread 3
// thread 3: continues with the instructions

async Task<List<Posts>> GetAllPosts()
{
    List<Posts> posts = await GetAllPosts().Wait();

    if (posts == null || posts.Count() == 0)
        return new List<Posts>();

    return posts;
}

// thread 1: initializes the posts variables
// thread 1: encounters the await keyword
// thread 1: spawns another thread: thread 2
// thread 2: locks the calling thread (thread 1) until GetAllPosts() is done
// thread 2: finishes the GetAllPosts() operation, free thread 1
// thread 1: continues with the instructions

using System.Collections.Generic;

public virtual ICollection<Enrollment> Enrollments { get; set; }

public struct TestStruct {
    // Fields, methods, properties and events ...
}

public class Keywords
{
    public static void Main()
    {
        int val1 = 0; // must be assigned a value;
        int val2; // optional

        Keywords1(ref val1);
        Console.WriteLine(val1);

        Keywords2(out val2);
        Console.WriteLine(val2);
    }

    static void Keywords1(ref int value) => value = 7;
    static void Keywords2(out int value) => value = 9; // must be defined
}

/* Output
   7
   9
*/

// optional arguments
public void ExampleMethod(int required, int optionalStr = "default string") { }

static void Main()
{
    // named arguments
    PrintOrderDetails(sellerName: "Gift Shop", 31, productName: "Red Mug");
}

static void PrintOrderDetails(string sellerName, int orderNum, string productName) {}

using System;
using System.Reflection;
using System.Reflection.Linq;

public class Program {
    public static void Main()
    {
        var members = typeof(object)
            .GetMembers(Bindingflags.Public |
                        BindingFlags.Static |
                        BindingFlags.Instance);

        foreach (var member in members)
        {
            bool inherited = member.DeclaringType.Equals(typeof(object).Name);
            Console.WriteLine($"{member.Name} is a {member.MemberType}," +
                              $"it has {(inherited ? "" : "not")} been inherited.");
        }
    }
}

using System;

public class Program {
    public static void Main()
    {
        var theString = "hello";
        var method = theString
            .GetType()
            .GetMethod("Substring",
                       new [] { typeof(int), typeof(int) }); // the types of the method

        var result = method.Invoke(theString, new object[] { 0, 4 });
        Console.WriteLine(result);
    }
}

var method = typeof(Math).getMethod("Exp");
var result = method.Invoke(null, new object[] { 2 }); // pass null as the first argument (no need for an instance)

Console.WriteLine(result); // e^2

public int AddFive(int pValue)
{
    int result;
    result = pValue + 5;
    return result;
}

public class MyInt
{
    public int MyValue;
}

public MyInt AddFive(int pValue)
{
    MyInt result  new MyInt();
    result.Myvalue = pValue + 5;
    return result;
}

using System;
using System.Threading;
using System.Threading.Tasks;

public class Program {
    public static void Main() {
        int[] Numbers = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 };

        // single-threaded:
        Console.WriteLine("Normal foreach loop: ");

        foreach (var number in Numbers)
            Console.WriteLine(longCalculation(number));

        // This is the Parallel (Multi-threaded solution):
        Console.WriteLine("Multiple threads: ");
        Parallel.forEach(Numbers, number =>
                         Console.WriteLine(longCalculation(number));
        );
    }

    private static int longCalculation(int number)
    {
        Thread.Sleep(1000); // sleep to simulate a long calculation
        return number * number;
    }
}

int length = people?.Length ?? 0;