using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System.Collections.Generic;
using System.Linq;


[MemoryDiagnoser(displayGenColumns: false)]
public partial class Program
{
  static void Main(string[] args) =>
    BenchmarkSwitcher.FromAssembly(typeof(Program).Assembly).Run(args);

  [Params (10, 10000)]
  public int Size { get; set; }
  private IEnumerable<int> items;

  [GlobalSetup]
  public void Setup()
  {
    items = Enumerable.Range(1, Size).ToArray();
  }  

  [Benchmark]
  public int Min() => items.Min();

  [Benchmark]
  public int Max() => items.Max();

  [Benchmark]
  public double Average() => items.Average();

  [Benchmark]
  public int Sum() => items.Sum();
}

public static int Min(this IEnumerable<int> source)
{
  if (source == null)
  {
    ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
  }

  int value;
  using (IEnumerator<int> e = source.GetEnumerator())
  {
    if (!e.MoveNext())
    {
      ThrowHelper.ThrowNoElementsException();
    }

    value = e.Current;
    while (e.MoveNext())
    {
      int x = e.Current;
      if (x < value)
      {
        value = x;
      }
    }
  }
  return value;
}

public static int Min(this IEnumerable<int> source) => MinInteger(source);

private static T MinInteger<T>(this IEnumerable<T> source)
  where T : struct, IBinaryInteger<T>
{
  T value;

  if (source.TryGetSpan(out ReadOnlySpan<T> span))
  {
    if (Vector.IsHardwareAccelerated && 
        span.Length >= Vector<T>.Count * 2)
    {
      .... // Optimized implementation
      return ....;
    }
  }
  .... //Implementation as in .NET 6
}

if (Vector.IsHardwareAccelerated && span.Length >= Vector<T>.Count * 2)

private static T MinInteger<T>(this IEnumerable<T> source)
where T : struct, IBinaryInteger<T>
{
  .... 
  if (Vector.IsHardwareAccelerated && span.Length >= Vector<T>.Count * 2)
  {
    var mins = new Vector<T>(span);
    index = Vector<T>.Count;
    do
    {
      mins = Vector.Min(mins, new Vector<T>(span.Slice(index)));
      index += Vector<T>.Count;
    }
    while (index + Vector<T>.Count <= span.Length);

    value = mins[0];
    for (int i = 1; i < Vector<T>.Count; i++)
    {  
      if (mins[i] < value)
      {
        value = mins[i];
      }
    }
  ....
}

using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNet.SignalR;

namespace SignalR05.Common
{
    public class OnlineUsersHub : Hub
    {
        public static readonly ConcurrentDictionary<string, string> OnlineUsers = new ConcurrentDictionary<string, string>();

        public void UpdateUsersOnlineCount()
        {
            // آی پی معرف یک کاربر است
            // اما کانکشن آی دی معرف یک برگه جدید در مرورگر او است
            // هر کاربر می‌تواند چندین برگه را به یک سایت گشوده یا ببندد
            var ipsCount = OnlineUsers.Select(x => x.Value).Distinct().Count();
            this.Clients.All.updateUsersOnlineCount(ipsCount);
        }

        /// <summary>
        /// اگر کاربران اعتبار سنجی شده‌اند بهتر است از
        /// this.Context.User.Identity.Name
        /// بجای آی پی استفاده شود
        /// </summary>        
        protected string GetUserIpAddress()
        {
            object environment;
            if (!Context.Request.Items.TryGetValue("owin.environment", out environment))
                return null;

            object serverRemoteIpAddress;
            if (!((IDictionary<string, object>)environment).TryGetValue("server.RemoteIpAddress", out serverRemoteIpAddress))
                return null;

            return serverRemoteIpAddress.ToString();
        }

        public override Task OnConnected()
        {
            var ip = GetUserIpAddress();
            OnlineUsers.TryAdd(this.Context.ConnectionId, ip);
            UpdateUsersOnlineCount();

            return base.OnConnected();
        }

        public override Task OnReconnected()
        {
            var ip = GetUserIpAddress();
            OnlineUsers.TryAdd(this.Context.ConnectionId, ip);
            UpdateUsersOnlineCount();

            return base.OnReconnected();
        }

        public override Task OnDisconnected()
        {
            // در این حالت ممکن است مرورگر کاملا بسته شده باشد
            // یا حتی صرفا یک برگه مرورگر از چندین برگه متصل به سایت بسته شده باشند
            string ip;
            OnlineUsers.TryRemove(this.Context.ConnectionId, out ip);
            UpdateUsersOnlineCount();

            return base.OnDisconnected();
        }
    }
}

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <script src="Scripts/jquery-1.6.4.min.js" type="text/javascript"></script>
    <script src="Scripts/jquery.signalR-1.1.3.min.js" type="text/javascript"></script>
    <script type="text/javascript" src='<%= ResolveClientUrl("~/signalr/hubs") %>'></script>
</head>
<body>
    <form id="form1" runat="server">
    online users count: <span id="usersCount"></span>
    </form>
    <script type="text/javascript">
        $(function () {
            $.connection.hub.logging = true;
            var onlineUsersHub = $.connection.onlineUsersHub;
            onlineUsersHub.client.updateUsersOnlineCount = function (count) {
                $('#usersCount').text(count);
            };
            $.connection.hub.start();
        });
    </script>
</body>
</html>

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Real-World Refactoring: Filtering products using a Builder Pattern 

<form #f="ngForm" (ngSubmit)="onSubmit(f.form)">
    <div class="panel panel-default">
        <div class="panel-heading">
            <h3 class="panel-title">
                Add Product
            </h3>
        </div>
        <div class="panel-body form-horizontal">
            <div class="form-group">
                <label for="productName" class="col col-md-2 control-label">Name</label>
                <div class="controls col col-md-10">
                    <input ngControl="productName" id="productName" required
                           #productName="ngForm"
                           (change)="log(productName)"
                           minlength="3"
                           type="text" class="form-control"
                           [(ngModel)]="productModel.productName"/>
                    <div *ngIf="productName.touched && productName.errors">
                        <label class="text-danger" *ngIf="productName.errors.required">
                            Name is required.
                        </label>
                        <label class="text-danger" *ngIf="productName.errors.minlength">
                            Name should be minimum {{ productName.errors.minlength.requiredLength }} characters.
                        </label>
                    </div>
                </div>
            </div>
            <div class="form-group">
                <label for="productCode" class="col col-md-2 control-label">Code</label>
                <div class="controls col col-md-10">
                    <input ngControl="productCode" id="productCode" required
                           #productCode="ngForm"
                           type="text" class="form-control"
                           [(ngModel)]="productModel.productCode"/>
                    <label class="text-danger" *ngIf="productCode.touched && !productCode.valid">
                        Code is required.
                    </label>
                </div>
            </div>
            <div class="form-group">
                <label for="releaseDate" class="col col-md-2 control-label">Release Date</label>
                <div class="controls col col-md-10">
                    <input ngControl="releaseDate" id="releaseDate" required
                           #releaseDate="ngForm"
                           type="text" class="form-control"
                           [(ngModel)]="productModel.releaseDate"/>
                    <label class="text-danger" *ngIf="releaseDate.touched && !releaseDate.valid">
                        Release Date is required.
                    </label>
                </div>
            </div>
            <div class="form-group">
                <label for="price" class="col col-md-2 control-label">Price</label>
                <div class="controls col col-md-10">
                    <input ngControl="price" id="price" required
                           #price="ngForm"
                           type="text" class="form-control"
                           [(ngModel)]="productModel.price"/>
                    <label class="text-danger" *ngIf="price.touched && !price.valid">
                        Price is required.
                    </label>
                </div>
            </div>
            <div class="form-group">
                <label for="description" class="col col-md-2 control-label">Description</label>
                <div class="controls col col-md-10">
                    <textarea ngControl="description" id="description" required
                              #description="ngForm"
                              rows="10" type="text" class="form-control"
                              [(ngModel)]="productModel.description"></textarea>
                    <label class="text-danger" *ngIf="description.touched && !description.valid">
                        Description is required.
                    </label>
                </div>
            </div>
            <div class="form-group">
                <label for="imageUrl" class="col col-md-2 control-label">Image</label>
                <div class="controls col col-md-10">
                    <input ngControl="imageUrl" id="imageUrl" required
                           #imageUrl="ngForm"
                           type="text" class="form-control"
                           [(ngModel)]="productModel.imageUrl"/>
                    <label class="text-danger" *ngIf="imageUrl.touched && !imageUrl.valid">
                        Image is required.
                    </label>
                </div>
            </div>
        </div>
        <footer class="panel-footer">
            <button [disabled]="!f.valid"
                    type="submit" class="btn btn-primary">
                Submit
            </button>
        </footer>
    </div>
</form>

import { Component } from 'angular2/core';
import { Router } from 'angular2/router';
import { IProduct } from './product';
import { ProductService } from './product.service';
 
@Component({
    //selector: 'product-form',
    templateUrl: 'app/products/product-form.component.html'
})
export class ProductFormComponent {
 
    productModel = <IProduct>{}; // creates an empty object of an interface
 
    constructor(private _productService: ProductService, private _router: Router) { }
 
    log(productName): void {
        console.log(productName);
    }
 
    onSubmit(form): void {
        console.log(form);
        console.log(this.productModel);
 
        this._productService.addProduct(this.productModel)
            .subscribe((product: IProduct) => {
                console.log(`ID: ${product.productId}`);
                this._router.navigate(['Products']);
            });
    }
}

<div class="form-group">
    <label for="description" class="col col-md-2 control-label">Description</label>
    <div class="controls col col-md-10">
        <textarea ngControl="description" id="description" required
                  #description="ngForm"
                  rows="10" type="text" class="form-control"
                  [(ngModel)]="productModel.description"></textarea>
        <label class="text-danger" *ngIf="description.touched && !description.valid">
            Description is required.
        </label>
    </div>
</div>

<input ngControl="productName" id="productName" required
       #productName="ngForm"
       (change)="log(productName)"
       minlength="3"
       type="text" class="form-control"
       [(ngModel)]="productModel.productName"/>

<textarea ngControl="description" id="description" required
          #description="ngForm"
          rows="10" type="text" class="form-control"></textarea>
<div class="alert alert-danger" *ngIf="description.touched && !description.valid">
    Description is required.
</div>

.ng-touched.ng-invalid{
    border: 1px solid red;
}

<div class="alert alert-danger" *ngIf="productName.touched && !productName.valid">
   Name is required.
</div>

<div *ngIf="productName.touched && productName.errors">
    <div class="alert alert-danger" *ngIf="productName.errors.required">
        Name is required.
    </div>
    <div class="alert alert-danger" *ngIf="productName.errors.minlength">
        Name should be minimum 3 characters.
    </div>
</div>

 <div *ngIf="productName.touched && productName.errors">
  {{ productName.errors | json }}

 Name should be minimum {{ productName.errors.minlength.requiredLength }} characters.

 <form #f="ngForm" (ngSubmit)="onSubmit(f.form)">

onSubmit(form): void {
   console.log(form);
}

<button [disabled]="!f.valid"
        type="submit" class="btn btn-primary">
    Submit
</button>

//same as before...
import { ProductFormComponent }  from './products/product-form.component';
 
@Component({
    //same as before…
    template: `
                //same as before…
                    <li><a [routerLink]="['AddProduct']">Add Product</a></li>
               //same as before…
    `,
    //same as before…
})
@RouteConfig([
    //same as before…
    { path: '/addproduct', name: 'AddProduct', component: ProductFormComponent }
])
//same as before...

 productModel = <IProduct>{}; // creates an empty object of an interface

<textarea ngControl="description" id="description" required
          #description="ngForm"
          rows="10" type="text" class="form-control"
          [(ngModel)]="productModel.description"></textarea>

addProduct(product: IProduct): Observable<IProduct> {
    let headers = new Headers({ 'Content-Type': 'application/json' }); // for ASP.NET MVC
        let options = new RequestOptions({ headers: headers });
 
    return this._http.post(this._addProductUrl, JSON.stringify(product), options)
        .map((response: Response) => <IProduct>response.json())
        .do(data => console.log("Product: " + JSON.stringify(data)))
        .catch(this.handleError);
}

 [HttpPost]
public ActionResult AddProduct(Product product)
{

 import { Headers, RequestOptions } from 'angular2/http';

//Same as before…
import { IProduct } from './product';
import { ProductService } from './product.service';
 
@Component({
//Same as before…
})
export class ProductFormComponent {
 
    productModel = <IProduct>{}; // creates an empty object of an interface
 
    constructor(private _productService: ProductService, private _router: Router) { }
 
    //Same as before… 

    onSubmit(form): void {
        console.log(form);
        console.log(this.productModel);
 
        this._productService.addProduct(this.productModel)
            .subscribe((product: IProduct) => {
                console.log(`ID: ${product.productId}`);
                this._router.navigate(['Products']);
            });
    }
}