fetchProducts(categoryId?: number) {
    console.log(categoryId);

    this.products = [];

    if (categoryId === undefined || categoryId.toString() === "undefined") {
      return;
    }

> npm install ng2-toasty --save

 npm ERR! Error: EPERM: operation not permitted, rename

"styles": [
    "../node_modules/bootstrap/dist/css/bootstrap.min.css",
    "../node_modules/ng2-toasty/bundles/style-bootstrap.css",
    "styles.css"
],

import { ToastyModule } from "ng2-toasty";

@NgModule({
  imports: [
    BrowserModule,
    ToastyModule.forRoot(),

 <ng2-toasty [position]="'top-right'"></ng2-toasty>

import { ToastyService, ToastOptions } from "ng2-toasty";

export class ProductGroupComponent implements OnInit {

  constructor(
    private productItemsService: ProductItemsService,
    private toastyService: ToastyService) { }

  fetchProducts(categoryId?: number) {
    console.log(categoryId);

    this.products = [];

    if (categoryId === undefined || categoryId.toString() === "undefined") {
      this.toastyService.error(<ToastOptions>{
        title: "Error!",
        msg: "Please select a category.",
        theme: "bootstrap",
        showClose: true,
        timeout: 5000
      });
      return;
    }

    this.productItemsService.getCategories().subscribe(
      data => {
        this.categories = data;
      },
      err => console.log("get error: ", err)
    );

> ng g cl app.error-handler

 installing class
  create src\app\app.error-handler.ts

import { ErrorHandler } from "@angular/core";

export class AppErrorHandler implements ErrorHandler {

  handleError(error: any): void {
    console.log("Error:", error);
  }
}

import { NgModule, ErrorHandler } from "@angular/core";
import { AppErrorHandler } from "./app.error-handler";

@NgModule({
  providers: [
    { provide: ErrorHandler, useClass: AppErrorHandler }
  ]

[HttpGet("[action]/{categoryId:int}")]
public async Task<IActionResult> GetProducts(int categoryId)
{
   throw new Exception();

    this.productItemsService.getProducts(categoryId).subscribe(
      data => {
        this.products = data;
        this.isLoadingProducts = false;
      }// ,
      // err => {
      //   console.log("get error: ", err);
      //   this.isLoadingProducts = false;
      // }
    );

import { ToastyService, ToastOptions } from "ng2-toasty";
import { ErrorHandler } from "@angular/core";

export class AppErrorHandler implements ErrorHandler {

  constructor(private toastyService: ToastyService) {
  }

  handleError(error: any): void {
    // console.log("Error:", error);
    this.toastyService.error(<ToastOptions>{
      title: "Error!",
      msg: "Fatal error!",
      theme: "bootstrap",
      showClose: true,
      timeout: 5000
    });
  }
}

 Uncaught Error: Can't resolve all parameters for AppErrorHandler: (?).

import { ErrorHandler, Inject } from "@angular/core";

export class AppErrorHandler implements ErrorHandler {

  constructor(
    @Inject(ToastyService) private toastyService: ToastyService
  ) {
  }

import { ToastyService, ToastOptions } from "ng2-toasty";
import { ErrorHandler, Inject, NgZone } from "@angular/core";
import { LocationStrategy, PathLocationStrategy } from "@angular/common";

export class AppErrorHandler implements ErrorHandler {

  constructor(
    @Inject(NgZone) private ngZone: NgZone,
    @Inject(ToastyService) private toastyService: ToastyService,
    @Inject(LocationStrategy) private locationProvider: LocationStrategy
  ) {
  }

  handleError(error: any): void {
    // console.log("Error:", error);

    const url = this.locationProvider instanceof PathLocationStrategy ? this.locationProvider.path() : "";
    const message = error.message ? error.message : error.toString();
    this.ngZone.run(() => {
      this.toastyService.error(<ToastOptions>{
        title: "Error!",
        msg: `URL:${url} \n ERROR:${message}`,
        theme: "bootstrap",
        showClose: true,
        timeout: 5000
      });
    });

    // IMPORTANT: Rethrow the error otherwise it gets swallowed
    // throw error;
  }
}

>npm install
>ng build --watch

>dotnet restore
>dotnet watch run

Domain Driven Design: The Good Parts

The greenfield project started out so promising. Instead of devolving into big ball of mud, the team decided to apply domain-driven design principles. Ubiquitous language, proper boundaries, encapsulation, it all made sense.
But along the way, something went completely and utterly wrong. It started with arguments on the proper way of implementing aggregates and entities. Arguments began over project and folder structure. Someone read a blog post that repositories are evil, and ORMs the devil incarnate. Another read that relational databases are last century, we need to store everything as a stream of events. Then came the actor model and frameworks that sounded like someone clearing their throat. Instead of a nice, clean architecture, the team chased the next new approach without ever actually shipping anything.
Beyond the endless technical arguments it causes, domain-driven design can actually produce great software. We have to look past the hype into the true value of DDD, what it can bring to our organizations and how it can enable us to build quality systems. With the advent of microservices, DDD is more important than ever - but only if we can get to the good parts. 

template:`
          <div><h1>{{pageTitle}}</h1>
               <div>My First Component</div>
          </div>
 `

 templateUrl: 'product-list.component.html'

<div class='panel panel-default'>
    <div class='panel-heading'>
        {{pageTitle}}
    </div>
    <div class='panel-body'>
        <div class='row'>
            <div class='col-md-2'>Filter by:</div>
            <div class='col-md-4'>
                <input type='text' />
            </div>
        </div>
        <div class='row'>
            <div class='col-md-6'>
                <h3>Filtered by: </h3>
            </div>
        </div>
        <div class='table-responsive'>
            <table class='table'>
                <thead>
                    <tr>
                        <th>
                            <button class='btn btn-primary'>
                                Show Image
                            </button>
                        </th>
                        <th>Product</th>
                        <th>Code</th>
                        <th>Available</th>
                        <th>Price</th>
                        <th>5 Star Rating</th>
                    </tr>
                </thead>
                <tbody>
 
                </tbody>
            </table>
        </div>
    </div>
</div>

import { Component } from 'angular2/core';
 
@Component({
    selector: 'pm-products',
    templateUrl: 'app/products/product-list.component.html'
})
export class ProductListComponent {
    pageTitle: string = 'Product List';
}

    <div>
        @RenderBody()
        <pm-app>Loading App...</pm-app>
    </div>

import { Component } from 'angular2/core';
 
@Component({
    selector: 'pm-app',
    template:`
    <div><h1>{{pageTitle}}</h1>
        <pm-products></pm-products>
    </div>
    `
})
export class AppComponent {
    pageTitle: string = "DNT AngularJS 2.0 APP";
}

 directives: [ProductListComponent]

import { Component } from 'angular2/core';
import { ProductListComponent } from './products/product-list.component';
 
@Component({
    selector: 'pm-app',
    template:`
    <div><h1>{{pageTitle}}</h1>
        <pm-products></pm-products>
    </div>
    `,
    directives: [ProductListComponent]
})
export class AppComponent {
    pageTitle: string = "DNT AngularJS 2.0 APP";
}

{{'Title: ' + pageTitle}}
{{2*20+1}}

{{'Title: ' + getTitle()}}

 <h1>{{pageTitle}}</h1>

 <h1 innerText={{pageTitle}}></h1>

 <table class='table' *ngIf='products && products.length'>

import { Component } from 'angular2/core';
 
@Component({
    selector: 'pm-products',
    templateUrl: 'app/products/product-list.component.html'
})
export class ProductListComponent {
    pageTitle: string = 'Product List';
    products: any[] = [
        {
            "productId": 2,
            "productName": "Garden Cart",
            "productCode": "GDN-0023",
            "releaseDate": "March 18, 2016",
            "description": "15 gallon capacity rolling garden cart",
            "price": 32.99,
            "starRating": 4.2,
            "imageUrl": "app/assets/images/garden_cart.png"
        },
        {
            "productId": 5,
            "productName": "Hammer",
            "productCode": "TBX-0048",
            "releaseDate": "May 21, 2016",
            "description": "Curved claw steel hammer",
            "price": 8.9,
            "starRating": 4.8,
            "imageUrl": "app/assets/images/rejon_Hammer.png"
        }
    ];
}

<tbody>
    <tr *ngFor='#product of products'>
        <td></td>
        <td>{{ product.productName }}</td>
        <td>{{ product.productCode }}</td>
        <td>{{ product.releaseDate }}</td>
        <td>{{ product.price }}</td>
        <td>{{ product.starRating }}</td>
    </tr>
</tbody>

در صورتیکه مقداری را به عنوان پیش فرض، به پارامتر این متد ارسال نکنید، مقدار پیش فرض آن از نوع استفاده شده بدست می‌آید.

شما می‌توانید برای دیکشنری نیز یک متد Get امن ایجاد کنید (در صورت عدم وجود کلید، بجای پرتاب استثناء، مقدار پیش فرض بازگشت داده شود).

public static class DictionaryExtensions
{
    public static TValue GetValueOrDefault< TKey, TValue >( this Dictionary< TKey, TValue > dic,
                                                            TKey key )
    {
        TValue result;
        return dic.TryGetValue( key,
                                out result )
            ? result
            : default(TValue);
    }
}

و روش استفاده

var names = new Dictionary< int, string >
            {
                { 0, "Vahid" }
            };
Console.WriteLine( names.GetValueOrDefault( 1 ) );

ZipFile in .NET

var startPath = Path.Combine( Environment.GetFolderPath( Environment.SpecialFolder.Desktop ), "Start" );
var resultPath = Path.Combine( Environment.GetFolderPath( Environment.SpecialFolder.Desktop ), "Result" );
var extractPath = Path.Combine( Environment.GetFolderPath( Environment.SpecialFolder.Desktop ), "Extract" );
Directory.CreateDirectory( startPath );
Directory.CreateDirectory( resultPath );
Directory.CreateDirectory( extractPath );

var zipPath = Path.Combine( resultPath, Guid.NewGuid() + ".zip" );
ZipFile.CreateFromDirectory( startPath, zipPath );
ZipFile.ExtractToDirectory( zipPath, extractPath );

#if DEBUG
#warning DEBUG is defined
#endif

#if DEBUG
#error DEBUG is defined
#endif

    Console.WriteLine("Normal line #1."); // Set break point here.
#line hidden
    Console.WriteLine("Hidden line.");
#line default
    Console.WriteLine("Normal line #2.");

static unsafe void Fibonacci()
{
    const int arraySize = 20;
    int* fib = stackalloc int[arraySize];
    var p = fib;
    *p++ = *p++ = 1;

    for ( var i = 2; i < arraySize; ++i, ++p )
    {
        *p = p[-1] + p[-2];
    }

    for ( var i = 0; i < arraySize; ++i )
    {
        System.Console.WriteLine( fib[i] );
    }
}

 >ng g m product --routing

import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';

const routes: Routes = [];

@NgModule({
  imports: [RouterModule.forChild(routes)],
  exports: [RouterModule]
})
export class ProductRoutingModule { }

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';

import { ProductRoutingModule } from './product-routing.module';

@NgModule({
  imports: [
    CommonModule,
    ProductRoutingModule
  ],
  declarations: []
})
export class ProductModule { }

 >ng g c product/ProductList

 installing component
  create src\app\product\product-list\product-list.component.css
  create src\app\product\product-list\product-list.component.html
  create src\app\product\product-list\product-list.component.spec.ts
  create src\app\product\product-list\product-list.component.ts
  update src\app\product\product.module.ts

import { ProductListComponent } from './product-list/product-list.component';

@NgModule({
  imports: [
  ],
  declarations: [ProductListComponent]
})
export class ProductModule { }

import { ProductListComponent } from './product-list/product-list.component';

const routes: Routes = [
  { path: 'products', component: ProductListComponent }
];

<nav class="navbar navbar-default">
  <div class="container-fluid">
    <a class="navbar-brand">{{title}}</a>
    <ul class="nav navbar-nav">
      <li>
        <a [routerLink]="['/home']">Home</a>
      </li>
      <li>
        <a [routerLink]="['/products']">Product List</a>
      </li>
    </ul>
  </div>
</nav>
<div class="container">
  <router-outlet></router-outlet>
</div>

import { ProductModule } from './product/product.module';

@NgModule({
  declarations: [
  ],
  imports: [
    BrowserModule,
    FormsModule,
    HttpModule,

    ProductModule,

    AppRoutingModule
  ],

products
products/:id
products/:id/edit

 >ng g m user --routing

import { UserModule } from './user/user.module';

@NgModule({
  declarations: [
  ],
  imports: [
    BrowserModule,
    FormsModule,
    HttpModule,

    ProductModule,
    UserModule,

    AppRoutingModule
  ],

 >ng g c user/login

import { LoginComponent } from './login/login.component';

const routes: Routes = [
  { path: 'login', component: LoginComponent}
];

<nav class="navbar navbar-default">
  <div class="container-fluid">
    <a class="navbar-brand">{{title}}</a>
    <ul class="nav navbar-nav">
      <li>
        <a [routerLink]="['/home']">Home</a>
      </li>
      <li>
        <a [routerLink]="['/products']">Product List</a>
      </li>
    </ul>
    <ul class="nav navbar-nav navbar-right">
      <li>
        <a [routerLink]="['/login']">Log In</a>
      </li>
    </ul>
  </div>
</nav>
<div class="container">
  <router-outlet></router-outlet>
</div>

 >ng g i user/user

export interface IUser {
    id: number;
    userName: string;
    isAdmin: boolean;
}

 >ng g s user/auth -m user/user.module

 installing service
  create src\app\user\auth.service.spec.ts
  create src\app\user\auth.service.ts
  update src\app\user\user.module.ts

import { IUser } from './user';
import { Injectable } from '@angular/core';

@Injectable()
export class AuthService {
  currentUser: IUser;

  constructor() { }

  isLoggedIn(): boolean {
    return !this.currentUser;
  }

  login(userName: string, password: string): boolean {
    if (!userName || !password) {
      return false;
    }

    if (userName === 'admin') {
      this.currentUser = {
        id: 1,
        userName: userName,
        isAdmin: true
      };
      return true;
    }

    this.currentUser = {
      id: 2,
      userName: userName,
      isAdmin: false
    };
    return true;
  }

  logout(): void {
    this.currentUser = null;
  }
}

import { Router } from '@angular/router';
import { AuthService } from './../auth.service';

import { Component, OnInit } from '@angular/core';
import { NgForm } from '@angular/forms';

@Component({
  selector: 'app-login',
  templateUrl: './login.component.html',
  styleUrls: ['./login.component.css']
})
export class LoginComponent implements OnInit {

  errorMessage: string;
  pageTitle = 'Log In';

  constructor(private authService: AuthService,
    private router: Router) { }

  ngOnInit() {
  }

  login(loginForm: NgForm) {
    if (loginForm && loginForm.valid) {
      let userName = loginForm.form.value.userName;
      let password = loginForm.form.value.password;
      if (this.authService.login(userName, password)) {
        this.router.navigate(['/products']);
      }
    } else {
      this.errorMessage = 'Please enter a user name and password.';
    };
  }
}

import { FormsModule } from '@angular/forms';

@NgModule({
  imports: [
    CommonModule,
    FormsModule,
    UserRoutingModule
  ],

<div class="panel panel-default">
  <div class="panel-heading">
    {{pageTitle}}
  </div>

  <div class="panel-body">
    <form class="form-horizontal" novalidate (ngSubmit)="login(loginForm)" #loginForm="ngForm" autocomplete="off">
      <fieldset>
        <div class="form-group" [ngClass]="{'has-error': (userNameVar.touched || 
                                               userNameVar.dirty) && 
                                               !userNameVar.valid }">
          <label class="col-md-2 control-label" for="userNameId">User Name</label>
          <div class="col-md-8">
            <input class="form-control" id="userNameId" type="text" 
                   placeholder="User Name (required)" required 
                   (ngModel)="userName" name="userName" #userNameVar="ngModel" />
            <span class="help-block" *ngIf="(userNameVar.touched ||
                                             userNameVar.dirty) &&
                                             userNameVar.errors">
                            <span *ngIf="userNameVar.errors.required">
                                User name is required.
                            </span>
            </span>
          </div>
        </div>

        <div class="form-group" [ngClass]="{'has-error': (passwordVar.touched || 
                                               passwordVar.dirty) && 
                                               !passwordVar.valid }">
          <label class="col-md-2 control-label" for="passwordId">Password</label>

          <div class="col-md-8">
            <input class="form-control" id="passwordId" type="password" 
                   placeholder="Password (required)" required 
                  (ngModel)="password" name="password" #passwordVar="ngModel" />
            <span class="help-block" *ngIf="(passwordVar.touched ||
                                             passwordVar.dirty) &&
                                              passwordVar.errors">
                            <span *ngIf="passwordVar.errors.required">
                                Password is required.
                            </span>
            </span>
          </div>
        </div>

        <div class="form-group">
          <div class="col-md-4 col-md-offset-2">
            <span>
               <button class="btn btn-primary"
                       type="submit"
                       style="width:80px;margin-right:10px"
                       [disabled]="!loginForm.valid">
                               Log In
               </button>
            </span>
            <span>
                <a class="btn btn-default"
                   [routerLink]="['/welcome']">
                     Cancel
                </a>
            </span>
          </div>
        </div>
      </fieldset>
    </form>
    <div class="has-error" *ngIf="errorMessage">{{errorMessage}}</div>
  </div>
</div>

import { Router } from '@angular/router';
import { AuthService } from './user/auth.service';
import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  pageTitle: string = 'Routing Lab';

  constructor(private authService: AuthService,
    private router: Router) { }

  logOut(): void {
    this.authService.logout();
    this.router.navigateByUrl('/welcome');
  }
}

<nav class="navbar navbar-default">
  <div class="container-fluid">
    <a class="navbar-brand">{{title}}</a>
    <ul class="nav navbar-nav">
      <li>
        <a [routerLink]="['/home']">Home</a>
      </li>
      <li>
        <a [routerLink]="['/products']">Product List</a>
      </li>
    </ul>
    <ul class="nav navbar-nav navbar-right">
      <li *ngIf="authService.isLoggedIn()">
        <a>Welcome {{ authService.currentUser.userName }}</a>
      </li>
      <li *ngIf="!authService.isLoggedIn()">
        <a [routerLink]="['/login']">Log In</a>
      </li>
      <li *ngIf="authService.isLoggedIn()">
        <a (click)="logOut()">Log Out</a>
      </li>
    </ul>
  </div>
</nav>
<div class="container">
  <router-outlet></router-outlet>
</div>