To create a download progress bar with a percentage in Angular, you can use the HttpClient module to request a server and track the download's progress. Here is an example of how this can be done,
    First, install the @angular/material and @angular/cdk packages in your Angular project:
    npm install @angular/material @angular/cdk

Import the MatProgressBarModule and MatProgressSpinnerModule modules from the @angular/material package in your Angular module:
import { MatProgressBarModule, MatProgressSpinnerModule } from '@angular/material';

@NgModule({
  imports: [
    MatProgressBarModule,
    MatProgressSpinnerModule
  ],
  // ...
})
export class AppModule { }

Now, import the HttpClient module and the HttpEventType enum from the @angular/common/http package:
import { HttpClient, HttpEventType } from '@angular/common/http';

Inject the HttpClient service into your component or service using the constructor:
constructor(private http: HttpClient) {}

Create a function to make the download request and track the progress:
public percentDone: number = 0;

public downloadFile() {
  this.http.get('https://example.com/file.zip', { responseType: 'blob' })
    .subscribe(event => {
      if (event.type === HttpEventType.DownloadProgress) {
        // Update the progress bar with the download percentage
        const this.percentDone = Math.round(100 * event.loaded / event.total);
        console.log(`Downloaded ${this.percentDone}%`);
      } else if (event.type === HttpEventType.Response) {
        // Save the downloaded file
        const file = new Blob([event.body], { type: 'application/zip' });
        const fileURL = URL.createObjectURL(file);
        window.open(fileURL);
      }
    });
}

In your component's template, use the mat-progress-bar and mat-progress-spinner components to display the progress bar and percentage:
<mat-progress-bar mode="determinate" [value]="percentDone"></mat-progress-bar>
<mat-progress-spinner mode="determinate" [value]="percentDone"></mat-progress-spinner>
<p>{{percentDone}}%</p>

You can use the percentDone property to bind to the value attribute of the mat-progress-bar and mat-progress-spinner components, as well as to display the percentage as text.

This is an example of how you can create a material design download progress bar with a percentage in Angular. You can customize the appearance and behaviour of the progress bar and percentage by using the various options and styles available for the mat-progress-bar and mat-progress-spinner components.

In my previous article Simple Way To Create Sqlite Database, I talked about the choice of the database and I focused on the simplest one which is Sqlite. But even if we choose the right one, we still need to work on the design and on its integration in the application side.

The old way of doing things was to use a database driver in your application, define the connexion and then execute the SQL command and queries from your code. When you get the data from the query execution, you need to parse them and then insert them to your objects. And this was a heavy task.

Later in time appeared Object-Relational Mapping. The ORM.

The ORM is the object-relational Mapping Tool. To make it simple, it's a tool that helps you to translate your database tables to a class Model in your application and vice versa. It also provides you with the methods to perform all the CRUD operation

The approach of creating the database then generating the class model is called Database First. The approach of creating the model in your application and then generating the database is called Code First.

In this article, we will focus on the database first part.

Entity Framework
Entity framework is the most commonly used ORM in .NET projects. It doesn't only allow you to access the database from your application. But also it also simplifies your life by giving you advanced possibilities like managing the concurrency and configuring your model. It has also the advantage of the use of the Language Integrated Query LINQ which is a powerful tool to perform your queries and filters.

Step 1: Nuget packages
    Create a new console project in visual studio.
    Open the commad line: Go to Tools => NuGet Package Manager => Package Manager Console and then you will get the command line displayed in your editor.

Install the required libraries by executing the following commands :

    PM>  Install-Package Microsoft.EntityFrameworkCore.Tools
    PM> install-Package Microsoft.EntityFrameworkCore.Sqlite
    Once you installed all packages you should have the following references in your solution

Step 2: Model generation

    To generate the model, you need to use also the command line
    You need to copy the needed database to your project folder and choose the right mode of copy to output directory:

Now you can generate your classes using the following command. You need to specify the output path, in our case it will be the folder Models
Scaffold-DbContext "Data Source=.\Database\products.db" Microsoft.EntityFrameworkCore.Sqlite -OutputDir Models
if everything is ok, you should get the classes generated under the folder Models and the following message in the package manager console should appear

The warning is there because the generator hardcoded the database's connection string in the code. You need to consider moving it in a protected way to a configuration file. But let's ignore it because it's not the main topic of this article.

Step 3: Check your generated classes
Now you should have the Context that contains the model creation and for each table you will get a class. In our case we have only one entity.

The Context class,
using System;
using System.Collections.Generic;
using Microsoft.EntityFrameworkCore;
namespace EntityFrameworkDbFirst.Models;
public partial class ProductsContext: DbContext {
    public ProductsContext() {}
    public ProductsContext(DbContextOptions < ProductsContext > options): base(options) {}
    public virtual DbSet < Item > Items {
        get;
        set;
    }
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    #warning To protect potentially sensitive information in your connection string, you should move it out of source code.You can avoid scaffolding the connection string by using the Name = syntax to read it from configuration - see https: //go.microsoft.com/fwlink/?linkid=2131148. For more guidance on storing connection strings, see http://go.microsoft.com/fwlink/?LinkId=723263.
        => optionsBuilder.UseSqlite("Data Source=.\\Database\\products.db");
    protected override void OnModelCreating(ModelBuilder modelBuilder) {
        modelBuilder.Entity < Item > (entity => {
            entity.HasKey(e => e.Barcode);
            entity.Property(e => e.Barcode).HasColumnType("VARCHAR");
            entity.Property(e => e.Brand).HasColumnType("VARCHAR");
            entity.Property(e => e.Name).HasColumnType("VARCHAR");
            entity.Property(e => e.PruchasePrice).HasColumnType("DOUBLE");
            entity.Property(e => e.SellingPrice).HasColumnType("DOUBLE");
        });
        OnModelCreatingPartial(modelBuilder);
    }
    partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
}

The class Item,
using System;
using System.Collections.Generic;
namespace EntityFrameworkDbFirst.Models;
public partial class Item {
    public string Barcode {
        get;
        set;
    } = null!;
    public string ? Name {
        get;
        set;
    }
    public string ? Brand {
        get;
        set;
    }
    public double ? PruchasePrice {
        get;
        set;
    }
    public double ? SellingPrice {
        get;
        set;
    }
}

Step 4: Write your cruds
Once you have created your model, you can now start performing operations on it. The following code in program.cs allows to add / update or delete an item.
You can test it and then see the results in the database directly.

It's a simple call to every method of the crud. You can play with it by changing the data and adding more controls.
For example if you call the AddItem twice without modifying it you will get an exception related to the constraint of the primary key
// See https://aka.ms/new-console-template for more information
using EntityFrameworkDbFirst.Models;
using System.Runtime.CompilerServices;
using static System.Net.Mime.MediaTypeNames;
using System.Xml.Linq;
try {
    Item item = new Item() {
        Barcode = "B12345678",
            Brand = "Milky Way",
            Name = "Milk",
            PruchasePrice = 20.5,
            SellingPrice = 25.5
    };
    // Uncomment this line if you want to test the delete method
    //DeleteItem("B12345678");
    AddItem(item);
    ////Uncomment this line if you want to test the update method
    //item.SellingPrice = 30;
    //UpdateItem(item);
    Console.WriteLine("Everything is Ok !");
} catch (Exception e) {
    Console.WriteLine(e.Message);
    if (e.InnerException != null) Console.WriteLine(e.InnerException.Message);
}
void AddItem(Item item) {
    using(var db = new ProductsContext()) {
        db.Items.Add(item);
        db.SaveChanges();
    }
}
//Delete the item
void DeleteItem(string Barcode) {
    using(var db = new ProductsContext()) {
        var item = db.Items.Find(Barcode);
        if (item == null) return;
        db.Items.Remove(item);
        db.SaveChanges();
    }
}
//Update the price of the item
void UpdateItem(Item item) {
    using(var db = new ProductsContext()) {
        db.Items.Update(item);
        db.SaveChanges();
    }
}

Step 4: And finally check your database
If you remember, we have set the property of the database in the solution explorer to "Copy if newer" so the file products.db is copied to the binary folder.
Open the database and browse your file then you will see the inserted item. Ensure that you left at least one product after testing the add and the delete

Here I recorded a video using MediaRecorder in Angular, So for that follow the below steps for a practical example.

Step 1
Install the @types/dom-mediacapture-record using below npm command
npm i @types/dom-mediacapture-record

No need to import this package into the app.module.ts file, We can directly use in our component.

Step 2
Add the below code to your tsconfig.json file for avoiding some elements-related errors.

tsconfig.json
"compilerOptions": {
    "strictPropertyInitialization": false
  },

If you have already added then avoid it.

Step 3
Now need to import some basic packages from @angular/core and declare the MediaRecorder variable into the component where you want to use it.

Here I am using the app.component.ts file
import {   Component,  ViewChild,  OnInit,  ElementRef} from '@angular/core';
declare var MediaRecorder: any;

Let's share the whole ts file code, Please refer to the below app.component.ts file code

import {Component,  ViewChild,  OnInit,  ElementRef} from '@angular/core';
declare var MediaRecorder: any;
@Component({
    selector: 'app-root',
    templateUrl: './app.component.html',
    styleUrls: ['./app.component.scss']
})
export class AppComponent implements OnInit {
    //Video Record and Play By Peter
    videoElement: HTMLVideoElement;
    recordVideoElement: HTMLVideoElement;
    mediaVideoRecorder: any;
    videoRecordedBlobs: Blob[];
    isRecording: boolean = false;
    downloadVideoUrl: string;
    stream: MediaStream;
    @ViewChild('recordedVideo') recordVideoElementRef: ElementRef;
    @ViewChild('liveVideo') videoElementRef: ElementRef;
    constructor() {}
    async ngOnInit() {
        navigator.mediaDevices.getUserMedia({
            video: {
                width: 480
            }
        }).then(stream => {
            this.videoElement = this.videoElementRef.nativeElement;
            this.recordVideoElement = this.recordVideoElementRef.nativeElement;
            this.stream = stream;
            this.videoElement.srcObject = this.stream;
        });
    }
    startVideoRecording() {
        this.videoRecordedBlobs = [];
        let options: any = {
            mimeType: 'video/webm'
        };
        try {
            this.mediaVideoRecorder = new MediaRecorder(this.stream, options);
        } catch (err) {
            console.log(err);
        }
        this.mediaVideoRecorder.start();
        this.isRecording = !this.isRecording;
        this.onDataAvailableVideoEvent();
        this.onStopVideoRecordingEvent();
    }
    stopVideoRecording() {
        this.mediaVideoRecorder.stop();
        this.isRecording = !this.isRecording;
    }
    playRecording() {
        if (!this.videoRecordedBlobs || !this.videoRecordedBlobs.length) {
            return;
        }
        this.recordVideoElement.play();
    }
    onDataAvailableVideoEvent() {
        try {
            this.mediaVideoRecorder.ondataavailable = (event: any) => {
                if (event.data && event.data.size > 0) {
                    this.videoRecordedBlobs.push(event.data);
                }
            };
        } catch (error) {
            console.log(error);
        }
    }
    onStopVideoRecordingEvent() {
        try {
            this.mediaVideoRecorder.onstop = (event: Event) => {
                const videoBuffer = new Blob(this.videoRecordedBlobs, {
                    type: 'video/webm'
                });
                this.downloadVideoUrl = window.URL.createObjectURL(videoBuffer);
                this.recordVideoElement.src = this.downloadVideoUrl;
            };
        } catch (error) {
            console.log(error);
        }
    }
}Put the same code in your component and verify once it is the correct one.Here I have created some functions regarding our video recording functionality, and If you want to try other mime types then you can use them according to your requirement,Refer to the below support mime types:"video/webm",
"audio/webm",
"video/webm;codecs=vp8",
"video/webm;codecs=daala",
"video/webm;codecs=h264",
"audio/webm;codecs=opus",
"video/mpeg",Step 4Put the HTML code as shown below app.component,html<div style="text-align:center">
  <h1 style="margin-bottom:30px;">Video Record Using Angular by Peter</h1>
  <video class="video" #liveVideo autoplay controls></video>
  <span class="m-1"></span>
  <video class="video" style="width:480px !important;" controls #recordedVideo></video>
  <br>
  <button class="btn btn-success btn-lg" *ngIf="!isRecording" (click)="startVideoRecording()">Start Recording</button>
  <button class="btn btn-warning btn-lg" *ngIf="isRecording" (click)="stopVideoRecording()">Stop Recording</button>
</div>If you want to get a better UI then please add the below script to your main index.html, Here I am sharing the whole index.html code you can use only CSS and js.index.html<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>Video Record by RG</title>
  <base href="/">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="icon" type="image/x-icon" href="favicon.ico">
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
    <link rel="stylesheet" href="https://unpkg.com/[email protected]/style.css">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js"></script>
</head>
<body>
  <app-root></app-root>
</body>
</html>

Let's save and run the app, Browser asks for your camera access give them.
And then click on Start Recording to start and Stop Recording to stop it. Once your recorder has done your recorded video show on right side.

You can play your recorded video by clicking on the play/pause icon.

This would be a series of articles, in this article, we would talk about out-of-box files code explanation and implement new custom APIs (to be covered in the next article)

It will cover the following things,

    What is NestJS? (covered in the previous article)
    Background (covered in the previous article)
    Installation (covered in the previous article)
    Hands-on Lab – Create a sample NestJS project (covered in the previous article)
    Hands-on Lab – Create custom API in the existing NestJS project (covered in the second article)
    In-depth Explanation - Out-of-the-box files (current article)

In-depth Explanation - Out-of-the-box files

Open Visual Code and see the project structure with the following files,

main.ts

    In the below code, the NestFactory method is imported as an entry point of the application. Next, the AppModule is imported from the previously discussed app. module file.
    Secondly, the bootstrap is marked as async and implemented. The main purpose of importing the bootstrap function is to call it for code execution.
    Then, the execution takes when the NestFactory.create() method is called the AppModule is passed as an argument to the root application module.
    This will attach a module by creating a new NestJS instance.
    The next step is to start the server by using the event listener method on the web server with port 3000.
    This method will return a promise indicating that the server has successfully started embarking on the await key.

app.module.ts

• In the below code snippet, the AppModule is imported as a method, and @Module decorator is imported from @nestjs/ sharing common library. The @Module decorator when passed consists of three properties namely imports, controllers, and providers.
• The specified controllers in the AppModule should always be the part of the array assigned to the property in the initial stage of the application development because the count of the controller is constrained to AppController which is the root module.
• And, the services should be made readily available in AppModule and hence be listed in the array assigned to the property of providers.

app.controller.ts
    The below code snippet is a simple demonstration of a controller in NestJS consisting of only one GET route. The class can be made a controller just by adding the @Controller decorator. It is also imported from the @nestjs/ which is a common library for all.
    The point here is to understand clearly that the controller usually relies on a service class.
    In the examples given AppController uses App service to implement the app.services.ts file by importing the corresponding statement that is added at the top.
    However, the process of inserting AppService into AppController is based on the method of Dependency Injection which by default adds the parameter of the same type.
    A default route is then implemented to handle the HTTP GET request through @Get decorator to implement getHello method.
    The method is therefore powered by AppService to fetch data and carry out request and response actions by returning at the same time.

app.services.ts file

• The below code snippet is a simple demonstration of a controller in NestJS consisting of only one GET route. The class can be made a controller just by adding the @Controller decorator. It is also imported from the @nestjs/ which is a common library for all.
• The point here is to understand clearly that the controller usually relies on a service class. In the examples given AppController uses Appservice to implement the app.services.ts file by importing the corresponding statement that is added at the top.
• However, the process of inserting AppService into AppController is based on the method of Dependency Injection which by default adds the parameter of the same type. A default route is then implemented to handle the HTTP GET request through @Get decorator to implement getHello method. The method is therefore powered by AppService to fetch data and carry out request and response actions by returning at the same time.

In this article, we talked about all the out-of-the-box files in detail and create a few custom APIs
Stay tuned for the next series of articles, hope you see you guys again soon.

Happy learning!

HostForLIFE.eu Node.js Hosting
HostForLIFE.eu is European Windows Hosting Provider which focuses on Windows Platform only. We deliver on-demand hosting solutions including Shared hosting, Reseller Hosting, Cloud Hosting, Dedicated Servers, and IT as a Service for companies of all sizes. We have customers from around the globe, spread across every continent. We serve the hosting needs of the business and professional, government and nonprofit, entertainment and personal use market segments.

We know Angular 15 is released on November 2022, so now in this article, we will see how to create an Angular 15 project. If you have already worked with angular previously you know, angular CLI helps us to build an angular application. Creating a new project in angular is now as simple as installing the Angular CLI and running the ng new command.

What is Angular CLI?
The Angular CLI helps us to create an Angular application and it uses Typescript, it creates an angular application with all the configuration files and the packages in one single command.

It helps us to add features (components, pipe, services, directives, etc.) to existing or new Angular applications.

How to create a new Angular 15 project
To create a new angular 15 project, first we need to set up the system environment

Installing Visual Studio Code
We need an editor to create the application so for that we need to install VS code. It is easy to install and helps us to create an angular application easily. You can download Visual Studio Code from the following link.

Node.Js
Node.js is the open source, cross-platform javascript run time environment.

Go to https://nodejs.org/en/

And install the LTS version
Install the Package Manager

To install Angular and its dependencies, we now need to install Node Package Manager (NPM).

NPM is the node.js package manager for JavaScript, which is automatically installed when we install node.js.

To see the version of NPM, run the below command on the Node.js command prompt like below
Node -v

Go to the Node.js command prompt and install typescript using the below command
Npminstall –gTypescript
Angular CLI (command line interface)

It is a tool that allows us to create a project using the command line argument.

So below is the command to create the latest angular project
npminstall -g @angular/cli@latest

Once the above command runs successfully, now check the latest version of angular and run the below command
Ngversion

Since I was already working on angular 14, so for me only I need to run the Angular CLI command.
Below is the image when my angular version is v14,

Now I ran below CLI command and then check the angular version like the below image
npminstall -g @angular/cli@latest

So this is the way we can upgrade the angular version to the latest version. You can also install the older version of Angular as shown below,

    MDAngular8
    cdAngular8
    npmi @angular/[email protected]

Now to create an Angular 15 application run the below command
NgnewAngular15App

Once you run the above command it will ask to install routing like below, give Y and press enter

After that, it will ask to add CSS like the below,

Once you press enter, it will take a few minutes to create the Angular 15 Application.

So from above, we can see, the angular 15 project creation is in progress.

From the above image, we can see, the angular 15 projects was created successfully. After creating this project, now let's open the VS code, go File tab then select the folder, and go to the directory where we created the angular 15 project, from there, select the angular15 project folder. Once you will load the project, you will see all files in VS code.

Now run the ng serve –o command, it will open the angular15 project like below

If you face an error like below then delete ng.ps1 file
PS C:\Users\DELL\Angular15App> ng serve -o

ng : File C:\Users\DELL\AppData\Roaming\npm\ng.ps1 cannot be loaded. The file C:\Users\DELL\AppData\Roaming\npm\ng.ps1 is not digitally signed.
You cannot run this script on the current system. For more information about running scripts and setting execution policies, see
about_Execution_Policies at https:/go.microsoft.com/fwlink/?LinkID=135170.

Then follow the below points then run ng serve –o again,
    Delete ng.ps1 from the directory C:\Users\% usernam%\AppData\Roaming\npm\
    Try to clear the npm cache directory C:\Users\%usernam%\AppData\ Roaming\npm-cache\

Note - Sometimes without clearing the cache also, the above error is resolved.
Now to verify that this application is created in Angular15, just go to the package.json file and see all the libraries are in v15 like below.

To build the application below is the command
ng build

To run the application below is the command
ng serve

after serving the application, go to the browser and enter the below URL, this is the default URL where the angular application run.
http://localhost:4200/

Angular Interceptor helps us modify the HTTP request by intercepting it before the request is sent to the backend. You can also change the incoming response from the backend. The Interceptor globally captures all incoming and outgoing requests in one place. We can use it to add custom headers to the outgoing request, log the incoming response, etc.

What is HTTP Interceptor?
An Angular HTTP interceptor sits between your application and the backend. When the application makes a request, the interceptor sees the request (HttpRequest) before sending it to the backend. You can access the request headers and body by intercepting the request. This allows us to transform the request before sending it to the server.

When the response (HttpResponse) arrives from the backend, interceptors can transform it before forwarding it to the application. One of the main advantages of HTTP interceptors is the ability to add an Authorization header to every request. You can do this manually, but it's tedious and error-prone. Another benefit is the ability to catch and log errors generated by requests.

How to Create Interceptor?
To implement an interceptor, we need to create an injectable service that implements the HttpInterceptor interface.
@Injectable() export class MyHttpInterceptor implements HttpInterceptor {

This class should implement the Intercept method
intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    //Do the code whatever you want with the HTTP request

    return next.handle(req);
}

This class is exposed in the root module using the HTTP_INTERCEPTORS injection token.
providers: [
    {
        provide: HTTP_INTERCEPTORS,
        useClass: MyHttpInterceptor,
        multi: true
    }
],

Interface: HTTP Interceptor
At the guts of the Interceptor, logic is the HttpInterceptor Interface. we have a tendency to should Implement it in our Interceptor Service.

The interface contains one method Intercept with the subsequent signature
intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>>

HTTP Request
The first argument is HttpRequest.

HttpRequest is an intercepted outgoing HTTP request. It integrates URLs, methods, headers, body, and various request configurations.

HttpRequest is an immutable class. In any way, we cannot accommodate genuine claims. To make adjustments, we want to duplicate the original request using the HttpRequest.clone

HTTP Handler
The second argument is httpHandler

HttpHandler sends the HttpRequest to the next Controller using the HttpHandler.handleMethod. The next handler can be another interceptor in on Thread or the Http Backend.

Let's see the example

Create MyHttpInterceptor.ts under /app folder and paste the below code
import {Injectable} from "@angular/core";
import {HttpEvent, HttpHandler, HttpInterceptor,HttpRequest} from "@angular/common/http";
import {Observable} from "rxjs/Observable";

@Injectable()
export class MyHttpInterceptor implements HttpInterceptor {
    constructor() {
    }

    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

        return next.handle(req);
    }
}

In the body of the method, you should be able to modify the HttpRequest object. Once done, you can select the HttpHandler.handle method from the HttpHandler with the HttpRequest object. The HttpHandler.handle method calls the fighter thus or sends a request to the main server.

App.Module
Whole code from the app module
import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { HttpClientModule,HTTP_INTERCEPTORS} from '@angular/common/http';
import { FormsModule } from '@angular/forms';

import { AppComponent } from './app.component';

import { GitHubService } from './github.service';
import {MyHttpInterceptor} from './MyHttpInterceptor';

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    HttpClientModule,
    FormsModule
  ],
  providers: [GitHubService,
    {
    provide: HTTP_INTERCEPTORS,
    useClass: MyHttpInterceptor,
    multi: true
  }
],
  bootstrap: [AppComponent]
})
export class AppModule { }

If you have faced any error regarding the import module please check your package.json file and install the required package if not installed.
So, here interceptor-adding process is done let's run the app and you can see every HTTP calls interceptor, You can put the debugger in the interceptor and see.
Let's add content type using interceptor

Content Type Adding
To modify the request we want to clone it using HttpRequest.clone
req = req.clone({ headers: req.headers.set('Content-Type', 'application/json') });

The header object is also unchanged. Therefore, we need to duplicate it using the headers.set method. The header.set method copies the current header and adds/modifies the new header value and returns the copied header.

We can also use the header.append. The append technique continually appends the header albeit the worth is already present.

And we can also remove the header like the one below shown
req = req.clone({ headers: req.headers.delete('Content-Type','application/json') });

If you want to add authorization token then we can add a token as shown below
const bearerToken: string =authService.Token; // here you can use your service method where get token
if (token) {
    req = req.clone({ headers: req.headers.set('Authorization', 'Bearer ' + bearerToken) });
}

So we can change or add code as per our requirement like adding logging, modifying response, catching the errors, etc...

We were developing a database project in .NET 6 using Entity Framework Core. Our back-end database engine was MySql rather than SQL server. It was a remote database. Short operations like single read and write worked fine but suddenly I stuck somewhere and got this horrible error.

The error was
“A second operation was started on this context instance before a previous operation was completed. This is usually caused by different threads concurrently using the same instance of DbContext.”

I started the operation again and surprisingly, this time the error was different regardless of the fact that all the inputs I provided were the same.

The error I got this time is:
The configured execution strategy 'MySqlRetryingExecutionStrategy' does not support user-initiated transactions. Use the execution strategy returned by 'DbContext.Database.CreateExecutionStrategy()' to execute all the operations in the transaction as a retriable unit.' ”

Please note that if you are using SQL Server as a database engine, You’ll receive SqlRetryingExecutionStrategy rather than MySqlRetryingExecutionStrategy.

I tested the application many times and explored the stack trace in detail and also do a lot of search online but failed to figure out the issue as my app followed all the suggested solution standards.

I started following a thread on github where one important thing was mentioned.

One has to be careful while working with sync and async method. If you are following sync method patterns in your code, better to follow it completely, mean use sync method in all of your codebase. Don’t mix sync calls with async calls in your code.

If you working with async methods in your code it is highly recommended to use the async method with await in all the places in your codebase.

This last line give me some hint to find out the issue so started exploring the code backward. From the position where error or exception was coming while going backward from line to line, there was an async function which has no await before its invocation.

As soon as I applied this await prior to this call, both errors are gone.

This would be a series of articles and in this article, we would talk about NestJS, its background, installation, and how it can be used to build APIs.

It will cover the following things,
    What is NestJS?
    Background
    Installation
    Hands-on Lab – Create a sample NestJS project

What is NestJS?
    NestJS is fairly a popular and cumulative JavaScript framework functioning under the hood of Node.js
    It is used to build scalable, reliable, and efficient server-side applications.
    The framework is directed with the Node.js environment and supports Typescript fully.
    It also can be scaled to make use of Express.js under the influence of Node.js
    NestJS is a full Typescript-supported framework, it can enable developers like you to code purely in JavaScript
    Also, it would let you combine the concepts of Object-Oriented Programming(OOP), Functional Reactive Programming(FRP), and purely Functional Programming(FP).

Background

    NestJS makes use of heavy usage of the server-side framework like Express under the hood of robust HTTP infrastructure.
    It can also be optionally configured to make use of Fastify as well although Express is considered as default.
    NestJS aims to provide a certain level of abstraction mechanism to the developers so that not only the common server-side frameworks like Fastify or Express are integrated internally but can also be exposed to the APIs chosen by the developer.
    These hidden bars provide developers to gain the freedom to use the third-party modules brightly and they can be made to motivate in the NestJS platform without having to operate the entire server side.

Installation
    All you need to do is to make sure you have Nest CLI is primarily installed on your local computer.
    If it is not installed, make use of the Node Package Manager (NPM) and follow up the approach using the commands given below.
    Also, you would need to make sure Node.js and NPM are preinstalled in your local system. If not, just follow the instructions to install Node.js at https://nodejs.org/
    $ npm i –g @nestjs/cli

Hands-on Lab – Create a sample NestJS project

Steps to be followed,
    Once the NestJS CLI installation is marked complete, it will readily be available to use the commands.
    Now let’s proceed with creating a sample project, and use the following control to initialize it.

    nest new nestjs-demo

    cd nestjs-demo

    Open Visual Code and see the project structure with the following files -

    main.ts - It is the application's entry point which consists of a method NestFactory.create() which creates a new instance of the Nest application.
    app.modules.ts: It contains the module of the application's implementation.
    app.controller.ts: It consists of only one routed implementation controller of NestJS.
    app.services.ts: It is the usual service method implementation.
    app.controller.specs.ts: It tests the file for the controller.

    Run the application by executing the below command and look at the browser with the output.

In this article, we talked about the overview and basic implementation of NestJS, in the next article, we would talk about all the out-of-the-box files in detail and create a few custom APIs. Stay tuned for the next series of articles, hope you see you guys again soon.

Happy learning!

When we sometimes create a new project but can't create the project because of an error like the one below.

Here I have provided steps to resolve the issue.

Step 1
Run CMD as Run as administrator mode.

Step 2
Uninstall angular cli.
npm uninstall -g @angular/cli

Step 3
Remove npm package files from the appdata folder.

Step 4
Open Run option by pressing Windows + R key. Then type %appdata% and press OK.

Step 5
Open the npm folder from the Roaming folder that you got in explorer.

Step 6
Delete ng and ng.cmd files from the npm folder if exists.
Open node_modules folder from there and delete @angular and angular/cli folder if exists.

Step 7
Reinstall the angular cli
npm install -g @angular/cli

Create a new Project with the use of command

App is created and run with ng serve command like this

For Angular Caching issue, a service worker is a script that runs in the web browser and manages caching for an application. Service workers augment the traditional web deployment model and empower applications to deliver a user experience with reliability and performance on par with code that is written to run on your operating system and hardware. Adding a service worker to an Angular application is one of the steps for turning an application into a Progressive Web App (also known as a PWA).

At its simplest, a service worker is a script that runs in the web browser and manages caching for an application.

Service workers function as a network proxy. They intercept all outgoing HTTP requests made by the application and can choose how to respond to them. For example, they can query a local cache and deliver a cached response if one is available. Proxying isn't limited to requests made through programmatic APIs, such as fetch; it also includes resources referenced in HTML and even the initial request to index.html. Service worker-based caching is thus completely programmable and doesn't rely on server-specified caching headers.

Unlike the other scripts that make up an application, such as the Angular application bundle, the service worker is preserved after the user closes the tab. The next time that browser loads the application, the service worker loads first, and can intercept every request for resources to load the application. If the service worker is designed to do so, it can completely satisfy the loading of the application, without the need for the network.

Even across a fast reliable network, round-trip delays can introduce significant latency when loading the application. Using a service worker to reduce dependency on the network can significantly improve the user experience.

Note:
Below, until Run the App with Service Worker, the procedure we follow are mainly from

Simulating a network issue
To simulate a network issue, disable network interaction for your application.

In Chrome:
    Select Tools > Developer Tools (from the Chrome menu located in the top right corner).
    Go to the Network tab.
    Select Offline in the Throttling dropdown menu.

Now the application has no access to network interaction.

For applications that do not use the Angular service worker, refreshing now would display Chrome's Internet disconnected page that says "There is no Internet connection".

Install Service Worker
We install the Service Worker by the command:
ng add @angular/pwa

The files are installed or changed are

    Changed:
        app.module.ts
        index.html
        angular.json
        package.json
        package-lock.json
    New Created:
        manifest.webmanifest
        ngsw-config.json
        assets\icons folder

The preceding command completes the following actions:

    Update app.module.ts file:
        Adds the @angular/service-worker package to your project.
        Enables service worker build support in the CLI.
        Imports and registers the service worker in the application module.

    Updates the index.html file:
        Includes a link to add the manifest.webmanifest file
        Adds a meta tag for theme-color

Installs icon files to support the installed Progressive Web App (PWA).

Creates installed icons registered file, called: manifest.webmanifest

Creates the service worker configuration file called ngsw-config.json, which specifies the caching behaviors and other settings.

    Updates the angular.json file, under "build"
        Register file: manifest.webmanifest
        Register file:  ngsw-config.json
        Register Servuce Worker as true

Updates the j.json file: the @angular/service-worker, 14.2.0 is added in dependencies

Install HTTP Server

Globally Installation via npm:
npm install --global http-server

Run the App with Service Worker
Note:
As we noticed the Service Worker installed is only registered to Build environment, not for Dev environment. So, to use Service Worker, we have to build the app.
ng build

Open the server at post 8080 for the project service-workers2:
    by command: http-server -p 8080 -c-1 dist/<project-name>

Run the app at port 8080 with Service Worker:

Select Offline in the Throttling dropdown menu.

With the addition of an Angular service worker, the application behavior changes. On a refresh, the page loads normally. Look at the Network tab to verify that the service worker is active.

NOTE:
Under the "Size" column, the requests state is (ServiceWorker). This means that the resources are not being loaded from the network. Instead, they are being loaded from the service worker's cache.
G - Verify if a service worker is registered #

To verify if a service worker is registered, use developer tools in your favorite browser.

In Firefox and Chromium-based browsers (Microsoft Edge, Google Chrome, or Samsung Internet):

    Open developer tools, then click the Application tab.
    In the left pane, select Service Workers.
    Check that the service worker's script URL appears with the status "Activated". (You'll learn what this status means in the lifecycle section in this chapter). On Firefox the status can be "Running" or "Stopped".

H - Summary
We demonstrated how to install Service Worker for solving Angular Caching issue.