ASP.NET MVC – Flashback of Important Concepts

A decade ago, ASP.NET Web Forms was the flagship framework for designing and developing web apps using .NET.

Over the years, developers had been demanding the ability to develop Web applications using a model-view-controller architecture. To address these needs and to stay current with the web development standards, Scott Guthrie of Microsoft designed the first ASP.NET MVC framework in October 2007.

Since then, a lot has changed in the world of ASP.NET MVC, but a lot is still the same. Although ASP.NET Core is the recommended option to develop web applications, as a developer, one should be aware of some important concepts that shaped the current framework.

This article provides an overview of the ASP.NET MVC technology for those who are still working on it, and explains some important components along the way.

Global Error Handler in ASP.NET Core

Error handling is crucial for any application. In Line-of-Business (LOB) ASP.NET applications, error handling can be implemented in multiple ways. Generally, when an application needs to perform data validations on data submitted by end-users, we implement data validations using annotations which is also known as Model validation

Model validation is limited with the Model class (aka entity class), but our application must be capable to validate code while executing - this is known as exception handling.

Traditionally, most of the programming languages provide try…catch…finally block for exception handling. There is nothing wrong in having a try…catch…finally block for every method in each class of the application, but it is always better to implement a global error or exception handler. By having a centralized exception handling, we can make our code more readable and maintainable.

In ASP.NET MVC applications we have exception action filters. Using this action filter, it is easier for the developer to implement global exception handler. I have already posted on MVC Exception Handling at this link

In the current article we will implement error handling in ASP.NET Core applications for WEB API. It is important to to have a global exception handler in WEB API so that the API action methods can remain clean, readable and maintainable.

ASP.NET Core provides a built-In middleware for global error handling, but we can also implement custom middleware or even we can write try...catch block for each action method. We will implement error handling with all these methods.

Dockerizing a Node, Express and MongoDB Application

In this tutorial, we will dockerize a Node,Express and Mongo Application. We will be using a Docker Linux container.

Let’s first take an overview of Docker and then we will directly jump to the implementation of the application.

What is Docker and why to use it?


When our applications are ready for  deployment, we have to configure a production machine with all the dependencies for the application. This is often a tedious and time consuming job. To make this approach easy, we can make use of Docker.

Docker provides a way to run applications securely and isolated in a container with all the applications dependencies packaged in it. Docker containers wrap up software and its dependencies into a standardized unit for software development. This makes sure that all the dependencies to run the application are packaged so that application will always run.

Some additional advantages of using Docker are:
  1. Once a docker image is created with all its dependencies, you need not worry about the operating system configuration for your application deployment. Since Docker is platform independent, a docker image that has successfully build  can run on any platform using docker.
  2. This docker image can be easily shared with a client (or anyone) who wants to use the application. They can run the application simply by installing docker on their machine.        
Docker can be downloaded from this link.

Login failed for user IIS APPPOOL\AppPool4.5 or APPPOOL\ASP.NET

The error ‘Login failed for user 'IIS APPPOOL\AppPool4.5’ usually occurs when you configure a new website in IIS or move an existing website to a newer version of IIS.

A simple solution to the error is to add a login to SQL Server for IIS APPPOOL\ASP.NET v4.5 and grant appropriate permission to the database.

Open SQL Server Management Studio > Right click ‘Security’ > New > Login

iis-apppool-login

Angular 6 Internationalization (with examples)

Angular is one of the most widely used front-end framework for modern web applications. The component-based design of Angular is suitable for modern web applications because each component can have its own UI, DataBinding, Events, etc.

We can use Angular with its object model to design and develop a web application's front-end. Since there could be several users requesting the web application from different parts of the globe, it is important for us to manage the rendering of the UI in a localized format.

Angular 6 Internationalization (i18n)

Angular framework has provided an Internationalization (i18n) tool. This tool helps developers to make application available in multiple languages.

The demo project discussed for this article is implemented using Angular-CLI. If you are new to Angular-CLI then please visit this link. Visual Studio Code, a free IDE tool, is used for this application. It can be downloaded from this link.

File Upload in ASP.NET Core

In one of the .NET Core trainings I was conducting recently, one of my students asked about uploading files using .NET Core application. Here's a solution. When we use ASP.NET MVC to upload a file, we use the HttpPostedFileBase class. This class is used to access the files uploaded by the client in an MVC application. In .NET Core, the IFromFile interface is used to represent a file that is sent with the HttpRequest. In this article we will use the IFromFile interface to upload the file. We will use Visual Studio 2017 and .NET Core 2.1. Information about the IFromFile interface can be read from this link.

Step 1: Open Visual Studio 2017 and create a new ASP.NET Core Web Application. Name this application as Core_FileUpload. Select the MVC project with .NET Core and ASP.NET Core 2.1 version for the project as shown in the following image:


mvc-app[8]


Using CSS Selection Pseudo-element to change the Default Selection Style of your WebPage

CSS Pseduo-elements allow you to style certain parts of a document. In this article, we will see how to change the default selection style of your web page contents using ::Selection PseudoElement.

Although you can use any webeditor of your choice, I am using Visual Studio 2013 for this demonstration. Let’s start by creating a new ASP.NET Web application. Start Visual Studio and click on New Project. Choose the Web Category and choose ASP.NET Web Application as shown below –

crtwebapp

HTML5 Picture Element for Responsive Images

In this article, we will look at the <picture> element and how it helps in responsive design to render images of different sizes, based on the physical device accessing the content.

To display an image in our HTML pages, we have so far made use of the <img/> element with the source [src] attribute. Here’s an example:

<img src="Images/default.png" alt="Default Logo" />

With varying screen sizes and pixels, handling this image becomes a challenge. Let's create a small example for demonstrating this. I am using the free Visual Studio Community Edition although you can use any other web editor of your choice. Create an empty web application and add a HTML page with the name TestPicture.html in our project. Add the following code: