.NET 8 Preview 1 is now available! This is the first preview of the next major version of .NET, which will include the next wave of innovations for web development with ASP.NET Core.

In .NET 8 we plan to make broad investments across ASP.NET Core. Below are some of the areas we plan to focus on: 

using System.Diagnostics.CodeAnalysis;

namespace CS8Tests;

[Experimental(diagnosticId: "Test001")]
public class ExperimentalAttributeDemo
{
    public void Print()
    {
        Console.WriteLine("Hello Experimental Attribute");
    }
}

var experimentalAttributeDemo = new ExperimentalAttributeDemo();

error Test001: 'CS8Tests.ExperimentalAttributeDemo' is for evaluation purposes only
and is subject to change or removal in future updates. Suppress this diagnostic to proceed.

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net8.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>

    <NoWarn>Test001</NoWarn>
  </PropertyGroup>
</Project>

#pragma warning disable Test001
var demo = new ExperimentalAttributeDemo();
#pragma warning restore Test001

using System.Diagnostics.CodeAnalysis;

namespace CS8Tests;

[Experimental(diagnosticId: "Test001")]
public class ExperimentalAttributeDemo
{
    [Experimental(diagnosticId: "Test002")]
    public void Print()
    {
        Console.WriteLine("Hello Experimental Attribute");
    }
}

var demo = new ExperimentalAttributeDemo();
demo.Print();

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net8.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>

    <NoWarn>Test001,Test002</NoWarn>
  </PropertyGroup>
</Project>

#pragma warning disable Test001,Test002
var demo = new ExperimentalAttributeDemo();
demo.Print();
#pragma warning restore Test001,Test002

function factorial(num) {
    if (num <= 1)
        return 1;
    else
        return num * factorial(num - 1);
}

function factorial(num) {
    if (num <= 1)
        return 1;
    else
        return num * arguments.callee(num - 1);
}

function factorial(num) {
    if (num <= 1)
        return 1;
    else
        return num * arguments.callee(num - 1);
}

var anotherFactorial = factorial;

factorial = function() {
    return 0;
}

alert(anotherFactorial(5));
alert(factorial(5));

window.color = "red";

var o = { color: "blue" };
o.showColor = sayColor;

function sayColor() {
    alert(this.color);
}

sayColor();
o.showColor();

function outer() {
    inner();
}

function inner() {
    alert(inner.caller);
}

inner();
outer();

    null

     function outer() {
        inner();
      }

function sayName(name) {
    alert(name);
}

function sum(num1,num2) {
    return num1 + num2;
}

function sayHi() {
    alert("Hi");
}

alert(sayName.length);
alert(sum.length);
alert(sayHi.length);

var color = "red";

var obj = { color: "blue" };

function sayColor(a, b) {
    alert(a + " said " + b + ": " + this.color);
}

sayColor("Sohrab", "Mitra");
sayColor.apply(this, ["Sohrab", "Mitra"]);
sayColor.call(this, "Sohrab", "Mitra");

sayColor.apply(obj, ["Sohrab", "Mitra"]);
sayColor.call(obj, "Sohrab", "Mitra");

var color = "red";

var obj = { color: "blue" };

function sayColor() {
    alert(this.color);
}

var bindSayColor = sayColor.bind(obj);
bindSayColor();

• قبلا «مؤلفه 2» ارجاعی را به «مؤلفه 1» داده است؛ لذا امکان ارجاع معکوس را در این حالت، نداریم.
  
• «مؤلفه 1» باید بتواند مستقل از «مؤلفه 2» نیز توزیع شده و کار کند؛ لذا این نیاز برای زمانی است که «مؤلفه 2» برای توزیع در Component Model ما وجود داشته باشد.
  
• نمی‌خواهیم در آینده برای نیازهای مشابه در همان صفحه‌ی X، تغییر جدیدی را در «مؤلفه 1» داشته باشیم (اضافه کردن خصوصیت مورد نظر به مدل نمایشی یا اصطلاحا ویو-مدل متناظر با گرید در در زمان طراحی، جواب مساله نمی‌باشد)
• می‌‌خواهیم به یک طراحی با Loose Coupling (اتصال سست و ضعیف، وابستگی ضعیف) دست پیدا کنیم.

public interface IConvention
{
}

public interface IExtraColumnConvention<T> : IConvention
{
   string Name { get; }
 
   string Title { get; }
 
   void Populate(IEnumerable<T> list);
}

• استفاده از API Reflection موجود در فضای نام System.Reflection 
  
• کلاس TypeDescriptor 

/// <summary>
/// Use this provider when you need access ExtraProperties with TypeDescriptor.GetProperties(instance)
/// </summary>
public class ExtraPropertyTypeDescriptionProvider<T> : TypeDescriptionProvider where T : class
{
    private static readonly TypeDescriptionProvider Default =
        TypeDescriptor.GetProvider(typeof(T));

    public ExtraPropertyTypeDescriptionProvider() : base(Default)
    {
    }

    public override ICustomTypeDescriptor GetTypeDescriptor(Type instanceType, object instance)
    {
        var descriptor = base.GetTypeDescriptor(instanceType, instance);
        return instance == null ? descriptor : new ExtraPropertyCustomTypeDescriptor(descriptor, instance);
    }

    private sealed class ExtraPropertyCustomTypeDescriptor : CustomTypeDescriptor
    {
      //...
    }
}

public class Column4Convention : IExtraColumnConvention<Product>
{
   public string Name => "Column4";
 
   public string Title => "Column 4"
 
   public void Populate(IEnumerable<Product> list)
   {
      //TODO: forEach on list and set ExtraProperty
      // item.ExtraProperty(Name,value)
      // item.ExtraProperty(Name,(obj)=> value)
      // item.ExtraProperty(Name,(obj)=> value, (obj,value)=>)
   }
}

public class Column2Convention : IExtraColumnConvention<Product>
{
   public string Name => "Column2";
 
   public string Title => "Column 2"
 
   public void Populate(IEnumerable<Product> list)
   {
      //TODO: forEach on list and set ExtraProperty
   }
}

public class Column3Convention : IExtraColumnConvention<Product>
{
   public string Name => "Column3";
 
   public string Title => "Column 3"
 
   public void Populate(IEnumerable<Product> list)
   {
      //TODO: forEach on list and set ExtraProperty
   }
}

var products = _productService.PagedList(page:1, pageSize:10);
var columns = _provider.GetServices<IExtraColumnConvention<Product>>();
foreach(var column in columns)
{
  column.Populate(products);
}

/*         A
         /   \
        B     C
        |    /|\
        D   E F G
        |
        H
        
*/

declare @t table
(
   id char(1) primary key not null,
   pid char(1) null --references @t
);

insert @t
values ('A', null), ('B','A'),('C','A'),
('D','B'), ('H','D'),('E','C'),('F','C'),('G','C');

with cte as 
(
select id
from @t 
where pid = 'A'

union all

select t.id
from cte c
join @t t
on t.pid = c.id
)
select * from cte

Design patterns are solutions to recurring problems; guidelines on how to tackle certain problems I have included implementations of some design patterns in C# to help beginners like me get their feet wet. 

In this episode, Robert is joined by Phil Japikse for a chat about design patterns. Software design patterns have been around long before the MVC Framework gained momentum. Phil starts with a review of Robert C. Martin's (Uncle Bob) SOLID macronym. After building the proper foundation,he reviews several design patterns, their C# implementation and when and how they should be used in modern software development.