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European ASP.NET Core Hosting :: A Quick And Simple Look Into .NET Core And Comparison To .NET Standard

clock July 16, 2019 11:54 by author Peter
First, as Microsoft simply described, .NET Core is an open-source, general-purpose development platform maintained by Microsoft and the .NET community on GitHub. .NET is cross-platform which supports Windows, macOS, and Linux and can be used to implement devices, cloud, and IoT applications. Historically, the .NET Framework had only worked on Windows devices. The Xamarin and Mono projects worked to bring .NET to mobile devices, macOS, and Linux. .NET Core provides a standard base library that can now be used across Windows, Linux, macOS, and mobile devices, still via Xamarin.

.NET Core has multiple characteristics such as cross-platform programming for Windows, Linux, MacOS, as well as consistency across architectures. It runs your code with the same behavior on multiple architectures, including x64, x86, and ARM. .NET Core provides flexible deployment, can be included in your app or installed side-by-side such as user-wide or system-wide installations, and can be used with Docker containers.

.NET Core makes it simpler for developers to build microservice architecture systems promptly. As such, systems include several independent and dynamic microservices, the developers can focus on specific microservices. .NET Core enables programmers to develop custom microservices by using varying programming languages, technologies, and frameworks. Likewise, the developers can build a robust system by combining multiple microservices flawlessly.

PROGRAMMING LANGUAGE SUPPORT
From a programming point of view C#, Visual Basic, and F# languages can be used to write applications and libraries for .NET Core. Additionally, with .NET Core 3.0 C# 8.0 will be supported. Currently, VB.NET compiles and runs on .NET Core, but the separate Visual Basic Runtime is not implemented. Microsoft announced that .NET Core 3 would include the Visual Basic Runtime.

GENERAL SUPPORTED FEATURES
.NET Core supports four cross-platform scenarios: ASP.NET Core web apps, command-line apps, libraries, and Universal Windows Platform apps. However, it does not presently apply Windows Forms or WPF which render the standard GUI for desktop software on Windows. Also, .NET Core 3 supports desktop technologies WinForms, WPF and UWP. Besides these, .NET Core supports the use of NuGet packages. Differently than before like .NET Framework, which is serviced using Windows Update, .NET Core depends on its package manager to get updates.

.NET Core consists of CoreCLR, a whole runtime implementation of the Common Language Runtime, which created at Microsoft as the virtual machine for handling execution of .NET programs and includes a just-in-time compiler called RyuJIT. Moreover, .NET Core also contains CoreRT, the .NET Native runtime enhanced to be integrated into AOT compiled native binaries.

.NET Core also includes CoreFX, which is a partial branch of .NET Framework standard libraries. While .NET Core shares a subset of .NET Framework APIs and comes with its own API that is not a subset of .NET Framework. Also, a variant of the .NET Core library is used for UWP.

.NET Core's command-line interface provides an execution entry point for operating systems and gives developer services similar compilation and package management.

Use .NET Core when

  • You want to build cross-platform applications
  • If the new application (web or service) needs to run on multiple platforms- Windows, Linux, macOS, choose .NET Core over .NET Framework. Visual Studio Code and third-party editors such as Sublime, Emacs, VI support .NET Core for cross-platform development.
  • The need is to build high-performance and scalable systems
  • When a performance-oriented and scalable system is on the list, it is better to prefer .NET Core over the .NET Framework. Reason being, .NET Core offers high-performance server runtime for Linux and Windows Server.
  • When you are using microservices or Docker containers
  • For applications or services that use microservices or Docker containers, opting .NET Core makes more sense. Reasons include,
    • .NET Core facilitates mixing microservices or services developed with Ruby, Java, .NET Framework, or other monolithic technologies.
    • Containers usually work in conjugation with microservices architecture. With .NET Framework, there is a limitation to work with Windows containers only. Moreover, while creating and deploying a container, the image size is smaller with .NET Core vs .NET Framework.
  • You need side-by-side .NET versions per application
  • For applications that may have a dependency on different versions of .NET for installation, opt for .NET Core. .NET Core offers side by side installation of multiple versions for .NET Core runtime on the same machine.

Use the .NET Framework when:

  • The app is using .NET technologies that are not available for .NET Core.
  • Several .NET technologies are not available for .NET Core. For example, ASP.NET web pages applications or workflow related services (WCF Data Services, Windows Workflow Foundation) are not included in. NET Core.
  • The existing app uses a platform that .NET Core does not support.
  • Some of the Microsoft or third-party services/platforms do not offer support to .NET Core. For example, Azure’s Service Fabric Stateful Reliable Services programming model does not support .NET Core and is available for.NET Framework.

Finally, the .NET Framework supports Windows and web applications. .NET Core is the new open-source and cross-platform framework to build applications for all operating systems including Windows, Mac, and Linux. .NET Core supports UWP and ASP.NET Core only.

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European ASP.NET Core Hosting :: Register And Use Multiple Implementations Of A Dependency In ASP.NET Core Dependency Injection

clock July 12, 2019 12:13 by author Peter

There can be situations where you need to register multiple implementations of the same dependency for your applications. For example, if you want to add features to your application without changing the existing code, a good way to do it is to add a new implementation for that. Your application needs to be written in a certain way to do this correctly. We have a really simple example that demonstrates this in this article. But when you eventually need to do this, ASP.Net Core built-in Dependency Injection providers capabilities to achieve this. In this article, we will look at how to do this with an example.
Registering Multiple Implementations of a Dependency

As an example, let’s take an online e-commerce website. This site gives Discounts to the customers on certain occasions and when certain conditions are met. I have an interface called IDiscount where it defines a discount and the logic to calculate it. For each type of discount, you want to provide in your e-commerce application, you can have an implementation of the IDiscount interface. Then I have an interface called IDiscountProcessor where the implementation of this interface handles calling all the implementations of IDiscount to calculate the final discount for a given Order.

You have a couple of ways to register multiple implementations of a dependency in ASP.Net Core. One way is to just use the provided extension methods on IServiceCollection to register your implementations with the desired lifetime.
    services.AddScoped<IDiscountProcessor, OrderDiscountProcessor>(); 
    services.AddScoped<IDiscount, SeasonalDiscount>(); 
    services.AddScoped<IDiscount, LargeOrderDiscount>(); 
    services.AddScoped<IDiscount, ThreeOrModeDiscount>();  


Here, I have registered the OrderDiscountProcessor implementation of IDiscountProcessor and 3 implementations of IDiscount interface.

This will work fine when we eventually resolve all the implementations of IDiscount interface we can calculate the total discount. But the problem comes when you have multiple registrations of the same implementation. For example, let’s say one of the developers accidentally registered SeasonalDiscount implementation twice. What will happen is that the Seasonal discount will be applied twice for all the orders, costing the organization money.

A better way of registering multiple implementations is to use TryAddEnumerable extension method given in the Microsoft.Extensions.DependencyInjection.Extensions namespace. This will not register any duplicate implementations making multiple implementation registration safe. The registration is a bit different where you need to use ServiceDescriptors to register the dependency. The modified implementation looks like this.
    services.AddScoped<IDiscountProcessor, OrderDiscountProcessor>(); 
    services.TryAddEnumerable(new[] 
    { 
        ServiceDescriptor.Scoped<IDiscount, SeasonalDiscount>(), 
        ServiceDescriptor.Scoped<IDiscount, LargeOrderDiscount>(), 
        ServiceDescriptor.Scoped<IDiscount, ThreeOrModeDiscount>() 
    }); 


Injecting and Using Multiple Implementations of a Dependency

Once your implementations are registered with the Dependency Injection container, they are ready to be used. To inject all the registered implementations, you need to use IEnumerable<> of the implementation type in your constructor. So, your constructor would look something like this. This is our OrderDiscountProcessor implementation.
    public class OrderDiscountProcessor : IDiscountProcessor 
    { 
        private readonly IEnumerable<IDiscount> _discounts; 
     
        public OrderDiscountProcessor(IEnumerable<IDiscount> discounts) 
        { 
            _discounts = discounts; 
        } 
        // ... 
    } 


Here I am injecting IEnumerable<IDiscount> where it injects all the registered implementations to my class. Then in my ProcessDiscount() method I can use the implementations like this.
    public (double, List<string>) ProcessDiscount(OrderViewModel order) 
    { 
        var discountDiscroptoons = new List<string>(); 
        var totalDiscount = 0.0; 
     
        foreach (var discount in _discounts) 
        { 
            var addedDiscount = discount.CalculateDiscount(order); 
            if (addedDiscount > 0) 
            { 
                 discountDiscroptoons.Add(discount.Description); 
            } 
            totalDiscount += addedDiscount; 
        } 
     
        return (totalDiscount, discountDiscroptoons); 
     } 


I can now iterate through all the implementations of IDiscount interface and call its CalculateDiscount() method to calculate the discount for the given Order.

Note that you can only use IEnumerable<> for your injections of multiple implementations. Any other type like IList<>, ICollection<> will not work in this case.
Summary

In this article, we looked into the process of how to register multiple implementations of the same dependency in ASP.NET Core and how to use these dependencies in our classes by injecting them. The simple sample application used to demonstrate this usage is available for download with this article or you can find the source code on GitHub under the following repository

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European ASP.NET Core Hosting :: How to Fix “An error occurred while starting the application” in ASP.NET Core on IIS

clock July 5, 2019 07:33 by author Scott

.NET Core is the latest Microsoft product and Microsoft always keep update their technologies. We have written tutorial about how to publish ASP.NET Core on IIS server, but we know that some of you sometimes receive error when deploying your ASP.NET Core. Feel frustrated to fix the issue? Yeah, not only you have headache, but some of our clients also experience same problem like you. That’s why we write this tutorial and hope it can help to fix your issue!

Anyone see this error? Have problem to solve it? We want to help you here!

The Problem

 

It basically means something bad happened with your application. Things you need to check

  • You might not have the correct .NET Core version installed on the server.
  • You might be missing DLL’s
  • Something went wrong in your Program.cs or Startup.cs before any exception handling kicked in

If you use Windows Server, then I believe that you can’t find anything on your Event Viewer too. You’ll notice that there is no error on your Event Viewer log. Why? This is because Event Logging must be wired up explicitly and you’ll need to use the Microsoft.Extensions.Logging.EventLog package, and depending on the error, you might not have a chance to even catch it to log to the Event Viewer.

How to Fix it?

So, how to fix error above? The followings are the steps to fix the error:

1. Open your web.config

2. Change stdoutLogEnabled=true

3. Create a logs folder

  • Unfortunately, the AspNetCoreModule doesn’t create the folder for you by default
  • If you forget to create the logs folder, an error will be logged to the Event Viewer that says: Warning: Could not create stdoutLogFile \\?\YourPath\logs\stdout_timestamp.log, ErrorCode = -2147024893.
  • The “stdout” part of  the value “.\logs\stdout” actually references the filename not the folder.  Which is a bit confusing.

4. Run your request again, then open the \logs\stdout_*.log file

Note – you will want to turn this off after you’re done troubleshooting, as it is a performance hit.

So your web.config’s aspNetCore element should look something like this

 <aspNetCore processPath=”.\YourProjectName.exe” stdoutLogEnabled=”true” stdoutLogFile=”.\logs\stdout” />

Doing this will log all the requests out to this file and when the exception occurs, it will give you the full stack trace of what happened in the \logs\stdout_*.log file

  

 

 

Hope this helps!

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European ASP.NET Core Hosting :: How to Host ASP.NET Core Application as a Windows Service

clock July 4, 2019 08:38 by author Scott

I recently came across the need to host a .NET Core web app as a Windows Service. In this case, it was because each machine needed to locally be running an API. But it’s actually pretty common to have a web interface to manage an application on a PC without needing to set up IIS. For example if you install a build/release management tool such as Jenkins or TeamCity, it has a web interface to manage the builds and this is able to be done without the need for installing and configuring an additional web server on the machine.

Luckily .NET Core actually has some really good tools for accomplishing all of this (And even some really awesome stuff for being able to run a .NET Core web server by double clicking an EXE if that’s your thing).

A Standalone .NET Core Website/Web Server

The first step actually has nothing to do with Windows Services. If you think about it, all a Windows Service is, is a managed application that’s hidden in the background, will restart on a machine reboot, and if required, will also restart on erroring. That’s it! So realistically what we first want to do is build a .NET Core webserver that can be run like an application, and then later on we can work out the services part.

For the purpose of this tutorial, I’m just going to be using the default template for an ASP.net Core website. The one that looks like this:

We first need to head to the csproj file of our project and add in a specific runtime (Or multiple), and an output type. So overall my csproj file ends up looking like:

<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup>
    <TargetFramework>netcoreapp2.1</TargetFramework>
    <RuntimeIdentifiers>win10-x64;</RuntimeIdentifiers>
    <OutputType>Exe</OutputType>
  </PropertyGroup> 

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.App" />
  </ItemGroup>
</Project>

Our RuntimeIdentifiers (And importantly notice the “s” on the end there) specifies the runtimes our application can be built for. In my case I’m building only for Windows 10, but you could specify other runtime monkiers if required.

Ontop of this, we specify that we want an outputtype of exe, this is so we can have a nice complete exe to run rather than using the “dotnet run” command to start our application. I’m not 100% sure, but the exe output that comes out of this I think is simply a wrapper to boot up the actual application dll. I noticed this because when you change code and recompile, the exe doesn’t change at all, but the dll does.

Now we need to be able to publish the app as a standalone application. Why standalone? Because then it means any target machine doesn’t have to have the .NET Core runtime installed to get everything running. Ontop of that, there is no “what version do you have installed?” type talk. It’s just double click and run.

To publish a .NET Core app as standalone, you need to run the following command from the project directory in a command prompt/powershell:

dotnet publish --configuration Release --self-contained -r win10-x64

It should be rather self explanatory. We are doing a publish, using the release configuration, we pass through the self contained flag, and we pass through that the runtime we are building for is Windows 10 – 64 Bit.

From your project directory, you can head to:  \bin\Release\netcoreapp2.1\win10-x64\publish

This contains your application exe as well as all framework DLL’s to run without the need for a runtime to be installed on the machine. It’s important to note that you should be inside the Publish folder. One level up is also an exe but this is not standalone and relies on the runtime being installed.

From your publish folder, try double clicking yourapplication.exe.

Hosting environment: Production
Content root path: \bin\Release\netcoreapp2.1\win10-x64\publish
Now listening on:
http://localhost:5000
Now listening on: https://localhost:5001
Application started. Press Ctrl+C to shut down.

In your browser head to http://localhost:5000 and you now have your website running from an executable. You can copy and paste this publish folder onto any Windows 10 machine, even a fresh install, and have it spin up a webserver hosting your website. Pretty impressive!

Installing As A Window Service

So the next part of this tutorial is actually kinda straight forward. Now that you have an executable that hosts your website, installing it as a service is exactly the same as setting up any regular application as a service. But we will try and have some niceties to go along with it.

First we need to do a couple of code changes for our app to run both as a service, and still be OK running as an executable (Both for debugging purposes, and in case we want to run in a console window and not as a service).

We need to install the following from your package manager console:

Install-Package Microsoft.AspNetCore.Hosting.WindowsServices

Next we need to go into our program.exe and make your main method look like the following:

public static void Main(string[] args)
{
 var isService = !(Debugger.IsAttached || args.Contains("--console"));
 var builder = CreateWebHostBuilder(args.Where(arg => arg != "--console").ToArray()); 

 if (isService)
 {

 var pathToExe = Process.GetCurrentProcess().MainModule.FileName;
 var pathToContentRoot = Path.GetDirectoryName(pathToExe);
 builder.UseContentRoot(pathToContentRoot);
 

 var host = builder.Build(); 

 if (isService)
 {
 host.RunAsService();
 }
 else
 {
 host.Run();
 }
}

This does a couple of things :

  • It checks whether we are using the debugger, or if we have a console argument of “–console” passed in.
  • If neither of the above are true, it sets the content root manually back to where the exe is running. This is specifically for the service runtime.
  • Next if we are a service, we use a special “RunAsService()” method that .NET Core gives us
  • Otherwise we just do a “Run()” as normal.

Obviously the main point of this is that if the debugger is attached (e.g. we are running from visual studio), or we run from a command prompt with the flag “–console”, it’s going to run exactly the same as before. Back in the day we used to have to run the service with a 10 second sleep at the start of the app, and quickly try and attach the debugger to the process before it kicked off to be able to set breakpoints etc. Now it’s just so much easier.

Now let’s actually get this thing installed!

In your project in Visual Studio (Or your favourite editor) add a file called install.bat to your project. The contents of this file should be:

sc create MyService binPath= %~dp0MyService.exe
sc failure MyService actions= restart/60000/restart/60000/""/60000 reset= 86400
sc start MyService
sc config MyService start=auto

Obviously replace MyService with the name of your service, and be sure to rename the exe to the actual name of your applications exe. Leave the %~dp0 part as this refers to the current batch path (Allowing you to just double click the batch file when you want to install).

The install file creates the service, sets up failure restarts (Although these won’t really be needed), starts the service, and sets the service to auto start in the future if the machine reboots for any reason.

Go ahead and create an uninstall.bat file in your project. This should look like:

sc stop MyService
timeout /t 5 /nobreak > NUL
sc delete MyService

Why the timeout? I sometimes found that it took a while to stop the service, and so giving it a little bit of a break inbetween stopping and deleting helped it along it’s way.

Important! For both of these files, be sure to set them up so they copy to the output directory in Visual Studio. Without this, your bat files won’t output to your publish directory.

Go ahead and publish your application again using our command from earlier:

dotnet publish --configuration Release --self-contained -r win10-x64

Now in your publish directory, you will find your install and uninstall bat files. You will need to run both of these as Administrator for them to work as installing Windows Services requires elevated access. A good idea is that the first time you run these, you run them from a command prompt so you can catch any errors that happen.

Once installed, you should be able to browse to http://localhost:5000 and see your website running silently in the background. And again, the best part is when you restart your machine, it starts automatically. Perfect!



European ASP.NET Core Hosting - HostForLIFE.eu :: Get Currency Format Using Google In ASP.NET

clock May 21, 2019 11:00 by author Peter

Many times, I have encountered a vital question: "How can I change 20000.00 to $20,000.00?" This involves a simple currency formatter. You can use either jQuery or server-side coding to show the currency in this format. Here, in this post, I will show you how to format the currency input from user in ASP.NET.
Format Currency using jQuery

First, start with jQuery. Google has provided a very simple way to format currency. You can find out about it from here. Or you can follow this.

To continue, you have to download two JavaScript files. One is jquery.formatCurrency-1.4.0.js and the second one is jquery.min.js. I have attached these JS files with the code I have attached along with this post.

So, let's start with sample coding. First, create a new project and add a new page, name it whatever you want. Then, add a new text box. Firstly, we will do it with the onBlur function of jQuery, so we don't need any more extra buttons for showing our formatted currency.

Add those downloaded JS files into your header section of the web form. And then, paste the following code into your page.

JS
    <script src="jquery.min.js"></script> 
    <script src="jquery.formatCurrency-1.4.0.js"></script> 
    <script type="text/javascript"> 
            $(document).ready(function () { 
                $('.text').focusout(function () { 
                    $('.text').formatCurrency(); 
                    $('.text').formatCurrency('.currencyLabel'); 
                }); 
            });        
    </script> 


HTML
    <div> 
         <p>Currency Formatter</p> 
         <asp:TextBox runat="server"  
     
         ID="txtPrice" CssClass="text"></asp:TextBox> 
         Show by Jquery: <span class="currencyLabel"></span> 
    </div> 


Check the CssClass of text box. It's the method by which formatCurrency() method is calling to format it to text box and also show the output value to a span.
Format Currency using C#

I hope it's clear to you how to format currency by jQuery. Now, let's see how to do this using C#. Don't worry, C# has an inbuilt function for this. For C#, we are taking an extra button to display the output into a label.

    <asp:TextBox ID="txtCurrency" runat="server"></asp:TextBox> 
    <asp:Button ID="btnChange" Text="Format" runat="server" OnClick="btnChange_Click"   /> 
    <asp:Label ID="lblShow" runat="server"></asp:Label> 
     
    protected void btnChange_Click(object sender, EventArgs e) 
    { 
        lblShow.Text = (Convert.ToDouble(txtCurrency.Text)).ToString("C2"); 
    } 


Make sure this method is only applicable to data types like decimal and double. So you have to add a check to see whether user input is bound to numbers.

 



European ASP.NET Core Hosting - HostForLIFE.eu :: Dependency Injection For Quartz.NET In .NET Core

clock May 14, 2019 12:18 by author Peter

Quartz.NET is a handy library that allows you to schedule recurring tasks via implementing IJob interface. Yet the limitation of it is that, by default, it supports only a parameterless constructor which complicates injecting external service inside of it, i.e., for implementing repository pattern. In this article, we'll take a look at how we can tackle this problem using standard .NET Core DI container.

The whole project referred to in the article is provided inside the following Github repository. In order to better follow the code in the article, you might want to take a look at it.

Project Overview
Let's take a look at the initial solution structure.

The project QuartzDI.Demo.External.DemoService represents some external dependency we have no control over. For the sake of simplicity, it does quite a humble job.

The project QuartzDI.Demo is our working project which contains simple a Quartz.NET job.
    public class DemoJob : IJob 
    { 
        private const string Url = "https://i.ua"; 
     
        public static IDemoService DemoService { get; set; } 
     
        public Task Execute(IJobExecutionContext context) 
        { 
            DemoService.DoTask(Url); 
            return Task.CompletedTask; 
        } 
    } 


It is set up in a straightforward way:
    var props = new NameValueCollection 
    { 
        { "quartz.serializer.type", "binary" } 
    }; 
    var factory = new StdSchedulerFactory(props); 
    var sched = await factory.GetScheduler(); 
    await sched.Start(); 
    var job = JobBuilder.Create<DemoJob>() 
        .WithIdentity("myJob", "group1") 
        .Build(); 
    var trigger = TriggerBuilder.Create() 
        .WithIdentity("myTrigger", "group1") 
        .StartNow() 
        .WithSimpleSchedule(x => x 
            .WithIntervalInSeconds(5) 
            .RepeatForever()) 
    .Build(); 
    await sched.ScheduleJob(job, trigger); 


We provide our external service via the job's static property.
    DemoJob.DemoService = new DemoService(); 

As the project is a console application, during the course of the article, we'll have to manually install all needed infrastructure and will be able to build a more thorough understanding of what .NET Core actually brings to the table.

At this point, our project is up and running. And what is most important is, it's dead simple, which is great. But we pay for that simplicity with a cost of application inflexibility, which is fine if we want to leave it as a small tool. But that's often not the case for production systems. So let's tweak it a bit to make it more flexible.
Creating a Configuration File

One of the inflexibilities is that we hard-code the URL we call into a DemoJob. Ideally, we would like to change it and also change it depending on our environment. .NET Core comes with an appsettings.json mechanism for that matter.

In order to start working with the .NET Core configuration mechanism, we have to install a couple of NuGet packages.

  • Microsoft.Extensions.Configuration 
  • Microsoft.Extensions.Configuration.FileExtensions 
  • Microsoft.Extensions.Configuration.Json 

Let's create a file with such a name and extract our URL there,
    { 
      "connection": { 
        "Url": "http://i.ua" 
      } 
    } 

Now, we can extract our value from the config file as below.
    var builder = new ConfigurationBuilder() 
                    .SetBasePath(Directory.GetCurrentDirectory()) 
                    .AddJsonFile("appsettings.json", true, true); 
    var configuration = builder.Build(); 
    var connectionSection = configuration.GetSection("connection"); 
    DemoJob.Url = connectionSection["Url"];
 

Note that to make it happen, we had to change the URL from constant to property.
    public static string Url { get; set; } 

Using Constructor Injection

Injecting service via a static property is fine for a simple project, but for a bigger one, it might carry several disadvantages: such as a job might be called without a service provided, thus failing or changing the dependency during the object runtime. To address these issues, we should employ constructor injection.

Although there is nothing wrong with Pure Dependency Injection and some people argue that you should strive for it, in this article, we'll use a built-in .NET Core DI container which comes with a NuGet package Microsoft.Extensions.DependencyInjection.

Now, let us specify a service we depend on inside constructor arguments.
    private readonly IDemoService _demoService; 
    public DemoJob(IDemoService demoService) 
    { 
        _demoService = demoService; 
    } 

In order to invoke a parameterful constructor of the job, Quartz.NET provides IJobFactory interface. Here's our implementation.
    public class DemoJobFactory : IJobFactory 
    { 
        private readonly IServiceProvider _serviceProvider; 
     
        public DemoJobFactory(IServiceProvider serviceProvider) 
        { 
            _serviceProvider = serviceProvider; 
        } 
     
        public IJob NewJob(TriggerFiredBundle bundle, IScheduler scheduler) 
        { 
            return _serviceProvider.GetService<DemoJob>(); 
        } 
     
        public void ReturnJob(IJob job) 
        { 
            var disposable = job as IDisposable; 
            disposable?.Dispose(); 
        } 
    } 


Let's register our dependencies.
    var serviceCollection = new ServiceCollection(); 
    serviceCollection.AddScoped<DemoJob>(); 
    serviceCollection.AddScoped<IDemoService, DemoService>(); 
    var serviceProvider = serviceCollection.BuildServiceProvider(); 


The final piece of the puzzle is to make Quartz.NET use our factory. IScheduler has property JobFactory just for that matter.
    sched.JobFactory = new DemoJobFactory(serviceProvider); 
    Using Options Pattern 


Now, we can pull the same trick with configuration options. Again, our routine starts with a Nuget package. This time Microsoft.Extensions.Options.

Let's create a strongly typed definition for configuration options.
    public class DemoJobOptions 
    { 
        public string Url { get; set; } 
    } 


Now, we populate them as below.
    serviceCollection.AddOptions(); 
    serviceCollection.Configure<DemoJobOptions>(options => 
    { 
        options.Url = connectionSection["Url"]; 
    }); 


And inject them into a constructor. Note that we inject IOptions<T>, not the options instance directly.
    public DemoJob(IDemoService demoService, IOptions<DemoJobOptions> options) 
    { 
        _demoService = demoService; 
        _options = options.Value; 
    } 


Conclusion
In this article, we've seen how we can leverage .NET Core functionality to make our use of Quartz.NET more flexible.

 

 



European ASP.NET Core Hosting :: Alert Dialog From Controller Without JavaScript In View

clock May 9, 2019 12:27 by author Peter
We can show an alert dialog in the browser from Controller without using any JavaScript in the View, which saves our time and makes the popping up of dynamic data way faster.
 
Displaying an Alert Dialog popup can be done from the controller and even from the server-side, but it is very useful when you want to display an alert using much less code.
 
In your Controller, copy the below code just before your return code.

public ActionResult SmartRegister(csUser model)  
 {               
     User us = new User();  
     rfSocietyEntities db = new rfSocietyEntities();  
     if (ModelState.IsValid)  
     {  
         int count = db.Users.Where(a => a.Email.Equals(model.Email)).Count();  
         if (count == 0)  
         {  
             us.Admin = model.Admin;  
             us.Email = model.Email;  
             us.FullName = model.FullName;  
             us.Password = model.Password;  
             us.PhoneNo = model.PhoneNo;  
             db.Users.Add(us);  
             db.SaveChanges();  
             return RedirectToAction("Dashboard""Dashboard");  
         }  
         else  
         {  
             TempData["msg"] = "<script>alert('Email id already registered.');</script>";  
             return View (model);  
         }  
     }  
     else  
     {  
         TempData["msg"] = "<script>alert('Please Check Data entered or try later.');</script>";  
         return View(model);  
     }  
}    
In your View file, add the below code.
  @Html.Raw(TempData["msg"])




European ASP.NET Core Hosting - HostForLIFE.eu :: ASP.NET Core Security Headers

clock April 30, 2019 11:13 by author Peter

With the help of headers, your website could send some useful information to the browser. Let’s see how it is possible to add more protection to your website.
To add a header for each request, we can use middleware.

XSS and CSP
Still in the OWASP top 10, there is XSS - Cross-Site Scripting attack. Sure, it helps a lot to encode symbols before displaying text on the website (using any one of the HtmlEncoder, JavaScriptEncoder, and UrlEncoder). And, it’s better never to use @Html.Raw(). But it is also possible to add a header that will inform the browser to stop XSS attack. This kind of header is useful mostly for old browsers.
app.Use(async (context, next) =>  
{  
context.Response.Headers.Add("X-Xss-Protection", "1");  
await next();  
}); 


For new browsers, it is better to use CSP. Here is how it is possible to add the CSP header.
app.Use(async (context, next) =>  
{  
context.Response.Headers.Add(  
  "Content-Security-Policy",  
  "default-src 'self'; " +  
  "img-src 'self' myblobacc.blob.core.windows.net; " +  
  "font-src 'self'; " +  
  "style-src 'self'; " +  
  "script-src 'self' 'nonce-KIBdfgEKjb34ueiw567bfkshbvfi4KhtIUE3IWF' "+  
  " 'nonce-rewgljnOIBU3iu2btli4tbllwwe'; " +  
  "frame-src 'self';"+  
  "connect-src 'self';");  
await next();  
});  


In this example, it is allowed to run scripts.js files only from the current website (that is a meaning of ‘self’). And it is allowed to run 2 specified with “nonce” attribute scripts that are inserted in page inside script tag. For example, if you are using some script like this one inside your page.
<script>  
function showMessage() {  
alert("Just for demo");  
}   
</script>  

Then, you will be not able to run this script without adding ‘unsafe-inline’ into your CSP definition.

But adding ‘unsafe-inline’ means leaving your website not-protected. So, better move the script into .js file or use a nonce. Just add to your script attribute nonce with some random value. For example,
<script nonce="KUY8VewuvyUYVEIvEFue4vwyiuf"> </script>  

Then, you can add to your CSP script-scr value ‘nonce-KUY8VewuvyUYVEIvEFue4vwyiuf’ and you will be able to run scripts from exactly this <script> section.

‘unsafe-inlne’ is also related to events that are added to your html as attributes. Like onclick, onchange, onkeydown, onfocus. For example, instead of the following onclick event, you should add id or class to your element and call event from <script> or .js file.
<p onclick="showMessage()">Show message</p>  

Like this,
<p id="message-text">Show message</p>  

<script nonce=”KUY8VewuvyUYVEIvEFue4vwyiuf”>  
$(document).ready(function() {  
$("#message-text") (function() {  
alert( "Just for demo" );  
});   
});  
</script>  


X-Frame-Options
By default, it is possible to display your website inside an iframe. But with one small header, it is possible to disallow this. Why? Because someone could display your website inside a frame and place a transparent layer over it. And, the users would be thinking that they are clicking on your website buttons/links but in a real case, they would be clicking on items placed in the transparent layer. And as cookies still could be in the user’s browser, some operation could be authenticated. This kind of attack is called Clickjacking. And, here is a header to protect your website from this attack.
context.Response.Headers.Add("X-Frame-Options", "DENY");  

Content sniffing
By the next link File Upload XSS you can find a more or less fresh sample of how it is possible to inject JavaScript into an svg file. And if a file like this would be located on the server that would have content sniffing security enabled, then JavaScript wouldn’t work because svg extension doesn’t correspond to JS content. Hope you believe me now that the next header is required.
context.Response.Headers.Add("X-Content-Type-Options", "nosniff");  

Referrer-Policy
One of the headers that is automatically added by browsers is “Referer”. It contains a site from which the user has been transferred. Sometimes, that is convenient for analytics. But sometimes, the URL could contain some private information that is better not to be disclosed.

If you don’t want to allow browsers to display your website as last visited in “Referer” header, please use the Referrer-Policy: no-referrer

Here is an example of all headers in one middleware.
app.Use(async (context, next) =>  
{  
context.Response.Headers.Add("X-Xss-Protection", "1");  
context.Response.Headers.Add("X-Frame-Options", "DENY");  
context.Response.Headers.Add("Referrer-Policy", "no-referrer");  
context.Response.Headers.Add("X-Content-Type-Options", "nosniff");  
              context.Response.Headers.Add(  
  "Content-Security-Policy",  
  "default-src 'self'; " +  
  "img-src 'self' myblobacc.blob.core.windows.net; " +  
  "font-src 'self'; " +  
  "style-src 'self'; " +  
  "script-src 'self' 'nonce-KIBdfgEKjb34ueiw567bfkshbvfi4KhtIUE3IWF' "+  
  " 'nonce-rewgljnOIBU3iu2btli4tbllwwe'; " +  
  "frame-src 'self';"+  
  "connect-src 'self';");  
await next();  
});  


Sure, you can read information about each one header and change value to something more appropriate for your needs.
Strict-Transport-Security

For activating Strict-Transport-Security - web security policy mechanism that helps to protect your website from protocol downgrade attacks and cookie hijacking, add the next one to your middleware pipeline (or just don’t remove it),
app.UseHsts();  

This middleware will add “Strict-Transport-Security” header

Removing Server Header
Sometimes, headers could provide some information that is better to hide. To disable the Server header from Kestrel, you need to set AddServerHeader to false. Use UseKestrel() if your ASP.NET Core version is  lower than 2.2 and ConfigureKestrel() if not.
WebHost.CreateDefaultBuilder(args)  
     .UseKestrel(c => c.AddServerHeader = false)  
     .UseStartup<Startup>()  
     .Build();



European ASP.NET Core Hosting :: Create A Typed HttpClient With

clock April 23, 2019 10:57 by author Peter

HttpClient is used for sending HTTP requests and receiving HTTP responses from a resource identified by a URI. But, HttpClient has some issues. To read more on the issues of HttpClient, you can check this link. In the .NET Core 2.1 release, Microsoft has introduced a new way of designing HttpClients to solve these issues, and it's called HttpClientFactory. HttpClientFactory is an opinionated factory, available since .NET Core 2.1, for creating HttpClient instances in our applications. This means that we can create HttpClients and can register them in the HttpClientFactory in our application and can leverage the dependency injection capabilities of the .NET core to inject these HttpClients in our code. HttpClientFactory allows us to no longer care about the lifecycle of the HttpClient by leaving it to the framework.
 
There are three ways to use HttpClientFactory to instantiate HttpClients.

  • Default client
  • Named client
  • Typed client

In order to use the factory, we need to register it in the DI container. So, we need to use an extension method AddHttpClient() on IServiceCollection interface in our Startup.cs class. This will allow us to inject the HttpClient in our class constructors.
 
In this article, we will see how to create a Typed HttpClient using the HttpClient factory in a .NET core MVC application and use it for making HTTP calls. I prefer Typed HttpClient over the other two because,

    As the name suggests, typed clients provide type safety.
    Typed clients help in encapsulating the API calls when we are making use of the HttpClient at one place, thus making our code DRY (Don't Repeat Yourself). The other two will scatter the implementation details of making HTTP calls throughout the codebase.

We will make a simple MVC application to learn the workings of typed HttpClient. This application will receive the name of a movie and call a REST API to fetch the details of that movie and shall display it to the user. I will be using Visual Studio Code for developing the application. The REST API used for fetching the movie details is the OMDB API. The OMDB API is a RESTful web service to obtain movie information. This is a free API with a 1000 requests per day limit for a user. We need an API key for accessing this API. To know more details about this API you can check their website.

Create a folder called MovieFinder and open it in VS Code. Create an MVC application by running the following command in the terminal.
    dotnet new mvc --name MovieFinder 

This shall create a basic .NET Core MVC application. Now, let’s create a View Model class to hold the data from the OMDB API. So, let’s add a class named MovieDetailModel.
    public class MovieDetailModel 
    { 
        public string Title { get; set; } 
        public string Year { get; set; } 
        public string Director { get; set; } 
        public string Actors { get; set; } 
        public string IMDBRating { get; set; } 
        public string PosterImage { get; set; } 
        public string Plot { get; set; } 
    } 


Now, we need to create an interface for our typed client. Let's name it IMovieDetailsClient.
    public interface IMovieDetailsClient 
    { 
        Task<MovieDetailModel> GetMovieDetailsAsync(string movieName); 
    } 


This interface contains a single method, GetMovieDetailsAsync, which accepts the movie name as the parameter and shall return the details of that movie. Now we need to create a class which implements this interface. This class shall contain the actual logic of calling the OMDB API to fetch the movie details.
    public class MovieDetailsClient : IMovieDetailsClient 
    { 
        private readonly HttpClient _httpClient; 
     
        public MovieDetailsClient(HttpClient httpClient) 
        { 
            httpClient.BaseAddress = new Uri("http://www.omdbapi.com/"); 
            _httpClient = httpClient; 
        } 
     
        public async Task<MovieDetailModel> GetMovieDetailsAsync(string movieName) 
        { 
            var queryString = $"?t={movieName}&apikey=<your-api-key>"; 
            var response = await _httpClient.GetStringAsync(queryString); 
     
            JObject json = JObject.Parse(response); 
     
            if (json.SelectToken("Response").Value<string>() == "True") 
            { 
     
                var movieDetails = new MovieDetailModel 
                { 
                    Title = json.SelectToken("Title").Value<string>(), 
                    Year = json.SelectToken("Year").Value<string>(), 
                    Director = json.SelectToken("Director").Value<string>(), 
                    Actors = json.SelectToken("Actors").Value<string>(), 
                    IMDBRating = json.SelectToken("imdbRating").Value<string>(), 
                    PosterImage = json.SelectToken("Poster").Value<string>(), 
                    Plot = json.SelectToken("Plot").Value<string>() 
                }; 
     
                return movieDetails; 
            } 
     
            return new MovieDetailModel 
            { 
                Title = movieName 
            }; 
        } 
    } 


In this class, we inject the HttpClient in our class constructor and set the base address of our OMDB API endpoint. We also implement GetMovieDetailsAsync method declared in our interface. We called the OMDB API from our method and mapped the API response to our view model and returned it. I have used the JSON.NET library for parsing the response from the API.
Note that I have hardcoded the API Base address and the API key in the code. This is not a healthy practice. We shall always prefer moving these kinds of values to configuration files and shall read those values from the configuration files in our code.
 
We have now created our typed client. Now let's create the view for user interaction. In the Index.cshtml file in the Views\Home folder, replace the existing code with the following code.
    @{ 
        ViewData["Title"] = "Home Page"; 
    } 
     
    @model MovieDetailModel 
     
    <form  
        asp-controller="Home"  
        asp-action="Submit" 
        method="post"  
        class="form-horizontal"  
        role="form"> 
     
        <div class="form-group"> 
            <label for="Title">Title</label> 
            <input  
                class="form-control"  
                placeholder="Enter Title" 
                asp-for="Title">    
        </div> 
        <button type="submit" class="btn btn-primary">Submit</button> 
    </form> 
     
     
    @{ 
        <br> 
         
        if(!string.IsNullOrEmpty(Model?.Year)) 
        { 
            var title = Model.Title; 
            var year = Model.Year;   
            var message = $"{title} is release on {year}";  
      
            <br> 
            <div class="card" style="width: 18rem;"> 
                <img class="card-img-top" src=@Model.PosterImage alt="Poster Not Available"> 
                <div class="card-body"> 
                    <h5 class="card-title">@Model.Title (@Model.Year)</h5> 
                    <p class="card-text">@Model.Plot</p>               
                </div> 
                <ul class="list-group list-group-flush"> 
                    <li class="list-group-item"><strong>Director : @Model.Director</strong></li> 
                    <li class="list-group-item"><strong>Actors : @Model.Actors</strong></li> 
                    <li class="list-group-item"><strong>Rating : @Model.IMDBRating</strong></li> 
                </ul> 
            </div>      
        } 
         
        if(Model != null && string.IsNullOrEmpty(Model?.Year)) 
        { 
            <div class="alert alert-danger" role="alert"> 
                <strong>Sorry!! Requested Movie Details are not available..</strong>  
            </div> 
        } 
    } 


Now, we need to add the Controller code for accepting the movie name from the view and for displaying the movie details. For that, we need to inject the typed client we had created into the constructor of our controller. So, we need to register this typed client with the HttpClient factory in our Startup.cs class. Add the following code in the ConfigureServices method in the startup class.
    services.AddHttpClient<IMovieDetailsClient, MovieDetailsClient>(); 

Now, let's add our controller methods. In the HomeController make the changes as below.
    public class HomeController : Controller 
    { 
        private readonly IMovieDetailsClient _movieDetailsClient; 
     
        public HomeController(IMovieDetailsClient movieDetailsClient) 
        { 
            _movieDetailsClient = movieDetailsClient; 
        } 
     
        public IActionResult Index() 
        { 
            return View(); 
        } 
     
        [HttpPost] 
        public async Task<IActionResult> Submit(MovieDetailModel model) 
        { 
            var movieDetail = await _movieDetailsClient.GetMovieDetailsAsync(model.Title); 
            return View("Index", movieDetail); 
        }       
    } 


We are injecting our IMovieDetails client in the constructor of our controller and assigning it to a read-only field _movieDetailsClient. We have also defined an action named Submit which takes the title of the movie from the view as a parameter. This method makes use of our typed HttpClient to fetch the details of that movie and shall return the view with the details of that movie.

Now, run the application. Execute the command dotnet run in the terminal. Open a browser and navigate to https://localhost:5001/.

 



European ASP.NET Core Hosting :: RESTful WebAPI With Onion Architecture

clock April 9, 2019 11:29 by author Peter

Hello friends, here I will show you how to create a WebApi with the following characteristics:

  • ASP.Core 2.1
  • EntityFramework
  • FluentValidation
  • Nlogger
  • Swagger
  • Jwt

Let's start. First create an empty project, then add the following folders:

  • Application
  • Domain
  • Service
  • Infrastructure

Then in the Domain folder, we create a library project Net.Core 2.1 with the name WebApi.Domain add the following dependencies

FluentValidation.AspNetCore

In this project, we add the following folders:

  • Dtos
  • Entities
  • Interfaces

In the Entities folder, we create the BaseEntity class:

    namespace WebApi.Domain.Entities 
    { 
        public abstract class BaseEntity 
        { 
            public virtual int Id { get; set; } 
        } 
    } 

Our project classes will inherit the field Id from this abstract class (if you want you can add other fields like CreatedAt or CreatedBy).

Then we create the Country class with the properties that defines a Country.

    namespace WebApi.Domain.Entities 
    { 
        public class Country : BaseEntity 
        { 
            public string Name { get; set; } 
            public int Population { get; set; } 
            public decimal Area { get; set; } 
            public string ISO3166 { get; set; } 
            public string DrivingSide { get; set; } 
            public string Capital { get; set; } 
     
        } 
    } 

Now to make the exercise more interesting, we are going to assume that we do not want to expose all the Country class. In the Dtos folder, we create the following CountryDensityDTO class.

    using System; 
    using WebApi.Domain.Entities; 
     
    namespace WebApi.Domain.Dtos 
    { 
        public class CountryDensityDTO : BaseEntity 
        { 
            public string Name { get; set; } 
            public string Capital { get; set; } 
            public decimal Area { get; set; } 
            public int Population { get; set; } 
     
     
            public int Populationdensity 
            { 
                get 
                { 
                    return Decimal.ToInt32(Population / Area); 
                } 
            } 
        } 
    }

This class exposes Name, Capital Area, Population and a calculated field Populationdensity.
Now we will continue with the Infrastructure layer and then we will finish the missing parts.We go to the Infrastructure folder and create a library Net.Core 2.1. We name it WebApi.Infrastructure.Data.

We add the following Packages:

  • Microsoft.EntityFrameworkCore.SqlServer 2.1.4
  • Microsoft.EntityFrameworkCore.Tools 2.1.4
  • Microsoft.Extensions.Identity.Stores 2.1.1
  • Microsoft.VisualStudio.Web.CodeGeneration.Design 2.1.5
  • Add Project reference WebApi.Domain 

We create the following folders:

  • Context
  • EntityDbMapping
  • Repository

In the Context Folder, we add the SqlServerContext class. We refer to our Country entity with DbSet to work with the database. As we work with CodeFirst approach, we will create a mapping for our entity Country in the database.
"modelBuilder.Entity<Country>(new CountryMap().Configure);"

Optionally, in this part we can also add seed data when creating a table.

using Microsoft.AspNetCore.Identity.EntityFrameworkCore; 
using Microsoft.EntityFrameworkCore; 
using WebApi.Domain.Entities; 
using WebApi.Infrastructure.Data.EntityDbMapping; 

namespace WebApi.Infrastructure.Data.Context 

public class SqlServerContext :   IdentityDbContext<ApplicationUser> 

    public DbSet<Country> Country { get; set; } 

    public SqlServerContext(DbContextOptions<SqlServerContext> options) : base(options) 
    { 
      
    }     
    protected override void OnModelCreating(ModelBuilder modelBuilder) 
    { 
        base.OnModelCreating(modelBuilder); 
        modelBuilder.Entity<Country>(new CountryMap().Configure); 
        // ModelBuilderExtensions.Seed(modelBuilder); 

    } 

//Data for first time on table 
public static class ModelBuilderExtensions 

    public static void Seed(this ModelBuilder modelBuilder) 
    { 
        modelBuilder.Entity<Country>().HasData( 
            new Country 
            { 
                Id = 1, 
                Name = "Venezuela", 
                Population = 300000000, 
                Area = 230103 
              
            }, 
            new Country 
            { 
                Id = 2, 
                Name = "Peru", 
                Population = 260000000, 
                Area =33249               
            } 
        ); 
    } 


In the folder, EntityDbMapping, we create the CountryMap class. In this class, we define the physical representation of the properties of the Country class as fields in the table of the database.

    using Microsoft.EntityFrameworkCore;   
    using Microsoft.EntityFrameworkCore.Metadata.Builders;   
    using WebApi.Domain.Entities;   
       
    namespace WebApi.Infrastructure.Data.EntityDbMapping   
    {   
        public class CountryMap : IEntityTypeConfiguration<Country>   
        {   
            public void Configure(EntityTypeBuilder<Country> builder)   
            {   
                builder.ToTable("Country");   
       
                builder.HasKey(c => c.Id);   
       
                builder.Property(c => c.Name)   
                    .IsRequired()   
                    .HasColumnName("Name")   
                    .HasColumnType("varchar(150)");   
       
                builder.Property(c => c.Population)   
                    .IsRequired()   
                    .HasColumnType("int")   
                    .HasColumnName("Population");   
       
                builder.Property(c => c.Area)   
                    .IsRequired()   
                    .HasColumnType("decimal(14,2)")   
                    .HasColumnName("Area");   
       
                builder.Property(c => c.ISO3166)   
                .IsRequired()   
                .HasColumnType("varchar(3)")   
                .HasColumnName("ISO3166");   
       
                builder.Property(c => c.DrivingSide)   
                .IsRequired()   
                .HasColumnType("varchar(50)")   
                .HasColumnName("DrivingSide");   
       
                builder.Property(c => c.Capital)   
                .IsRequired()   
                .HasColumnType("varchar(50)")   
                .HasColumnName("Capital");   
            }   
       
        }   
    }   


This is it for now.
In the next chapter, we will implement validations with FluentValidation. We will also configure Mapper to use it with our DTOs and will implement Identity using Jwt.



About HostForLIFE.eu

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