Lets see what happens

Introduction to JavaScript

 Hello folks, I hope you are having a great day. Today, I am going to start this new tutorial series on JavaScript and here's our 1st tutorial titled Introduction to JavaScript. This is a beginner level tutorial series, where we will start from very basics & will slowly move towards complex concepts. If you're not a beginner or looking for secure development training or advanced tutorials, stay tuned, more training is coming. We can use any development Editor for running JavaScript and for this tutorial series, I will use Microsoft Visual Studio Code, which is free to use & you can download it from official site. You don't need to be an expert programmer, in order to learn JavaScript, but you must have some basic knowledge of HTML & CSS. So, let's get started with today's lecture:

What is JavaScript - A Quick Definition

  • JavaScript ( initially named as LiveScript, officially named as ECMAScript ) is a client-side scripting language, developed by Brendan Eich in 1995 and is used to create interactive webpages and mostly used in game development.
  • Before JavaScript, webpages were dull and has no way to interact with the user, as we had only server side languages ( php, java etc. ) at that time and in order to get any action done, we have to send request to the server.
  • With JavaScript, now we can perform any complex task without refreshing the page, JavaScript works on client side that's why there's no need of page refreshing.
  • You must have noticed on your Facebook / Twitter profile that they update automatically, that's because of JavaScript.
  • As JavaScript is a client side language so it can't communicate directly with the server i.e. database or file system.
  • JavaScript is normally confused with Java, but they are two entirely different languages, Java is server side complex language while JavaScript is a simple scripting language.
How to Run JavaScript Code?
  • As I mentioned earlier, JavaScript is a client side scripting language, so we don't need any compiler or editor for running JavaScript.
  • Instead, JavaScript is directly executed by the web Browsers, similar to HTML & CSS, which are also client side languages.
  • When a user makes an HTTP request, then browser reads the webpage and along with HTML,CSS etc. it also finds the JS scripts and executes them.
  • All modern browsers support JavaScript and you can enable / disable JavaScript in your browser's settings.
  • Moreover, JavaScript works on almost all operating platforms i.e. Windows, Linux, Mac, Ubuntu etc.
  • So, in order to run JavaScript, you can use any Programming Environment / Editor i.e. Sublime, Notepad++, Visual Studio Code etc.
Uses of JavaScript
So, now let's have a look at few uses / advantages of Javascript:
  1. Developing Mobile Applications & Games.
  2. Web Browser-based Games.
  3. Add interaction to websites.
  4. Back end web Development.
  5. Rich interface for Applications and web pages.

How to Include a JavaScript Code in HTML WebPage

  • As I have mentioned earlier, we don't need any editor to run or execute JavaScript. Instead, web browsers execute the JS code on their own.
  • But question is, How web Browsers are going to recognize that its a JS code ??
  • And the answer is, the code placed between <script> </script> tags will be treated as a JavaScript Code.
  • There are two ways to include the JavaScript code in an HTML webpage, discussed as follows:
Embedding JavaScript Code directly in HTML Page
  • When we add JavaScript directly in <body> tag of our HTML page, it is termed as Embedded JavaScript.
  • In our HTML page, we can place JavaScript Code in the <script> </script> tags, as shown in the figure:
  • You can see in the figure that I have added a simple JavaScript Code:

<script> alert(“I am learning JavaScript”);    </script>

  • To run this code you have to add an extension. Go to the left side of visual studio and click on extension or press Ctrl + Shift + X buttons. 
  • Afterwards, Search “Open in browser” and install the first file. Look below in the image for more detail.
  • When your exertion is installed, now go back to your HTML file and press Alt + B.  It will run your code. 
  • You will see something similar to below image, in your browser.
  • This is a simple JavaScript alert message, displaying our content.
Include External JavaScript File in HTML WebPage
  • If we add JavaScript Code directly in HTML page then it will make the code quite messy.
  • So, it's always a best practice to create a separate file for JavaScript ( extension .js ) and then include this file in your webpage.
  • By convention, If your JavaScript code is more than 10 lines, then it's better to add an external JavaScript file.
  • It also reduces the code repetition i.e. if you are using your JS code for multiple pages.
  • Let's see now, how to add an external JavaScript file:
Steps to Follow:
  • Create a new file by pressing Ctrl + N and add  “alert("Introduction to JavaScript");”  content in this file. Save it with the name “Test.js”.
  • As you can see on the right side in the figure.
  • Now go back to the “index.html” file and add the code as you can see in below figure:
  • When you will refresh the web browser then it will automatically reload a JS file through source code, as shown in below figure:
What Is The Best Way To Include JavaScript File in Html
  • You can add <script> tag in the <head> section of your HTML file, in the start of the <body> tag and also at the start or end of the body tag.
  • But I would advise you to add it at the end of the <body> tag. I will show you why it should be at the bottom of the body tag.
  • The HTML page always loads from top to bottom. And if your JS file will be in <head> tag or opening of the <body> tag. Therefore, it’s gonna run JavaScript first before loading any of the content in and it will leave a negative impact on your webpage. Let me show you now how it will drop a negative impression on your website.
  • Here is a basic example for you. As you can see in below image that I have added <script> tag at the start of <head> tag and add a new tag of <h1> for your understanding.
  • Save these file and press ALT + B to execute this code. You will notice that as you see in the picture underneath that only <script> tag alert comes up first without loading the rest of page.
  • But once I click at ok then it has loaded the rest of the page now. As indicated in the image here.
 
  • It leaves a bad impact on users because the page is loading step by step but not at once. Now I am gonna add  <script> at the bottom of the <body> tag and as you can see in image down.
  • Now save it go again to the browser and reload the page.  Instantly you can see the content and alert form at the same time. This is a perfect way of adding JS.
I am sure you all already know HTML and CSS but you have attempted to learn JavaScript many times but failed for some reason and you drop it. But I am sure now you are going to stick with me since I am going to describe you step by step each code. From the next lesson onward, I am going to tell you more in detail what is the Syntax of JavaScript and where to place JavaScript file. I hope you guys understand this lesson and I will see you in my next tutorial. Till then take care of yourself. If YOU have any question regarding this post feel free to comment below and ask about it.  I will definitely reply to your query as soon as possible. 

How to perform Software Testing and Debugging

Hello everyone, I hope you are having a fine day. In today’s tutorial, I am going to discuss “Software Testing and Debugging”

During testing and debugging, seek advice for the various techniques of detecting and eliminating mistakes in a program, so that it produces the desired result. Every programmer needs to be aware of the truth that a program does not always run perfectly for the first time. It is consequently vital to make efforts in case you do stumble on the errors. First, determine and note any errors which are found during the very first building and running of the program.

Errors that Occur during Initialization of the Program

Many errors can occur when running a program, some apparent, and others are not. All these mistakes can be grouped under four types, namely: syntax errors, run-time errors, logical mistakes, and latent mistakes.

Syntax problems are any violation of regulations specified within a  programming language results in syntax mistakes. The compiler during the build and run process of the code will automatically define such errors. When syntax errors are found in the source code of the program, the compilation fails and terminates after listing the errors and the line numbers within the source code of the application where the errors have occurred. 

Remember, in a few cases, the line quantity won't precisely suggest the vicinity of the mistake. In different instances, syntax error can also result in an extended listing of mistakes. Correction of one of the mistakes at the beginning of the build of the system may also take away the entire listing.

Run-time mistakes  include mismatch of data types or referencing out-of-variety array details, go undetected by the compiler. An application with those mistakes will run. However, it produces misguided consequences. It should be noted that isolating run-time blunders is usually a hard challenge.

Logical errors: As the name suggests, these mistakes are related to the common sense of program execution. Such moves as taking a wrong direction, failure to forget a particular situation, and incorrect order of assessment of statements belong to this category. Logical mistakes do now not show up as collect-generated mistakes messages. Rather, the program outputs the wrong results during execution. These errors are due to adverse information and incorrect translation of the set of rules by the program.

Latent errors are a 'hidden' error that pops up when a particular set of information is used — for instance, subsequent declaration.

Various Ways of  Testing a Program

Testing is the process of reviewing and executing a program to detect mistakes, which can belong to any of the four types mentioned above. We know that while the compiler can locate syntactic and semantic errors, it can't come across run-time and logical mistakes that show up all through the execution of the program. Testing, therefore, should include vital steps to detect all viable mistakes in the software. It is important to remember that it is miles impractical to find all the mistakes. The testing procedure can also encompass the subsequent two degrees:

  • Human testing
  • Computer-based trying out

Human checking out is a powerful error-detection procedure and finishes earlier than the computer-based tryout. Human testing methods encompass code inspection by the programmer, code inspection with the aid of a test institution, and a review by an essay writing service or a peer organization. The test is achieved through a statement and is analyzed with a tick list of common programming mistakes. In addition to finding the errors, the programming style and preference of algorithms are also reviewed.

Computer-based testing entails a list of degrees, particularly the compiler tryout and run-time check out. Compiler testing is the most effective of the two and also detects undiscovered syntax errors. The software executes while the compiler detects greater mistakes. 

Should this mean that this system is correct? Will it produce the expected consequences? The answer is no. The software might comprise both run-time and logical errors, which in any case won't affect the compiling process of the program.

Program Debugging And Error Checking 

Debugging is the process of discovering and correcting the mistakes in a program’s source code. One simple technique of debugging is locating print statements or logs output by the compiler during the build process of the system that shows the values of variables. It displays the dynamics of a program and allows us to observe and compare statistics at various points. Once the area of a blunder is recognized and is error corrected, the debugging statements may be eliminated. We can use the conditional compilation statements, to switch on or off the debugging statements.

Another method is to use the technique of deduction. The area of a blunder is arrived at by the use of elimination and refinement. It is done through the listing of possible reasons for the mistake.

In Conclusion

Two critical resources of a computer gadget are execution time and memory. The performance of an application is measured in phrases of those two sources. Efficiency can be progressed with true design and coding practices.

Thank you so much for reading this article. If you have any question regarding this article, you can comment below and ask us. We are looking forward for your feedback.

Introduction to Entity Framework Core
Departments:
  1. Computer Engineering
  2. Computer Science
Codings:
  1. C#
Softwares:
  1. Microsoft Visual Code
  2. Microsoft Visual Studio
Hello friends, I hope you all are doing great. In today's tutorial, we will have a look at detailed Introduction to Entity Framework Core. It's our 16th tutorial in ASP.NET Core series. So far, we have covered the the MVC architecture and few concepts related to object oriented programming and now we are ready to get our hands on Databases. So, today we will cover data handling in detail, which is done by Entity Framework Core in .NET Core applications. So, let's first understand this Entity Framework Core:

Introduction to Entity Framework Core

  • Entity Framework Core ( normally called EF Core ), designed by Microsoft, is an open source, flexible, extensible, lightweight and cross-platform framework, which is used for storing & retrieving data from database.
  • EF Core creates a bridge between Objects in Programming & relational databases, thus referred as Object-Relational Mapper. ( O/RM )
  • In simple words, EF Core acts as a middle layer between our .NET Core Application & database.
  • EF Core is written from scratch for .NET Core, but also works with standard .NET 4.5+, and is an enhancement of ADO.NET.
Why need Entity Framework Core ?
  • If you have worked on any database i.e. SQL, MYSQL, Oracle etc. then you must have the idea about query strings.
  • In order to send or request data from these databases, we need to use query strings, which are normally quite lengthy and prone to errors.
  • In order to avoid this direct interaction with databases using query strings, we have many third party frameworks which handle these underlying query strings themselves and provide programmers with easy programming methods to deal with the data.
  • Entity Framework Core is an official data handling framework designed by Microsoft and works perfectly with ASP.NET Core.
  • EF Core supports a wide range of relational database using third party libraries called database providers, we install these libraries as NuGet Packages.
  • For example, if I want to work on SQL database, then I will install SQL NuGet Package, we will install one later.
EF Core Approach
  • We can use two approaches in Entity Framework Core, which are:
    • Code First Approach
    • Database First Approach
  • We have very limited support available for "Database First Approach" for now and we use this approach, when we already have the database. ( will cover it in future lectures )
  • In Code First Approach, we design our database from scratch and using dbContext class, we transfer data from  app to database & vice versa.
EF Core Package
  • Now we need to select the type of database i.e. SQL, MYSQL, Oracle etc., which we want to use for our web application, so I am going to use Sql Database.
  • In order to use SQL Database with EF Core, we need to install its NuGet Package called Microsoft.EntityFrameworkCore.SqlServer.
  • This NuGet package is actually the Database provider, so if you are using any other database i.e. MYSQL, then you need to install its NuGet Package. ( We will install one in the next section )
  • SQL Server NuGet Package has a dependency on EF Core Relational Package called Microsoft.EntityFrameworkCore.Relational.
  • Relational package contains the functionality, that are common in all relational databases i.e. SQL, MYSQL, Oracle etc.
  • This relational package, in turn has a dependency on Main EF Core Package called Microsoft.EntityFrameworkCore.
  • That's the main base EF Core NuGet Package that will enable EF Core on our web App.

How to Install Entity Framework Core

  • Now, let's install EF Core on our web application, so right click on the Project's Name in Solution Explorer.
  • Now click on Manage NuGet Packages, and NuGet Package Manager will open up.
  • In the Browser tab, make a search for EntityFrameworkCore.SqlServer and you will get results, as shown in below figure:
  • You can see in above figure that first one appeared in the search, is our required NuGet Package, so let's install this one.
  • As this SQL NuGet Package has a dependency on Relational, which in turn has dependency on EF Core, so when we install SQL Server Package, the other two will automatically be installed by the Visual Studio.
  • So, click on the Install Button and then accept the terms and this SQL Server NuGet Package will be installed.
  • After complete installation, you need to open Dependencies in Solution Explorer, as shown in figure on right side.
  • You will find Packages in Dependencies, so open it up and inside it you will find our SQL Server NuGet Package.
  • Expand this SQL Server Package and you will find its dependencies i.e. Relational etc.
  • So, we have successfully installed Entity Framework Core for SQL Database on our web app.
So, that was all for today. We have successfully installed EF Core on our web application but we haven't yet created our SQL Database. In the next video, we will have a look at DbContext Class in Entity Framework Core. Till then take care & have fun !!!

Form Validation in ASP.NET Core
Departments:
  1. Computer Engineering
  2. Computer Science
Codings:
  1. C#
Softwares:
  1. Microsoft Visual Code
  2. Microsoft Visual Studio
Hello friends, I hope you all are doing great. In today's tutorial, we will have a look at Form Validation in ASP.NET Core. It's our 15th tutorial in ASP.NET Core series. In our previous lecture, we have created a Registration Form for our engineering website. But we haven't added any validations on the submitted data. So, even if users don't fill any boxes and just hit the Register Button, a new user will be created without any personal info. So, today we will place some checks on these text boxes to validate the user submitted data. So, let's get started with it:

Form Validation in ASP.NET Core

  • Validations in ASP.NET Core are available in the form of attributes & Tag Helpers.
  • Validation Attributes are applied on Properties in Model classes and validate the user submitted data.
  • Validation Tag Helpers are used in Views and provide validation errors to the users.
  • So, let's add few validations to our registration form and show errors, if inappropriate data is submitted.

Validation Attributes in ASP.NET Core

  • ASP.NET Core has many builtin Validation Attributes to verify the incoming data, few of them are as follows:
    • [Required] : Value is required.
    • [Regular Expression] : Value must match the regular expression provided.
    • [Compare] : Compares two properties i.e. Verify Email.
    • [Range] : Value must lie between specified range.
    • [MinLength] : Specifies the value's minimum length.
    • [MaxLength] : Specifies the value's maximum length.
    • [DataType] : Value must be of specified datatype.
  • So, let's apply few of these Validation Attributes on our Properties in Engineers.cs file, placed in Models folder.
  • We have already linked these properties with text boxes using asp-for Tag Helper.
  • So, open this file & in Engineers class, place these validation attribute before properties, as shown in below figure:
  • As you can see in above figure that before Username property, I have used two validation attributes i.e. Required & MaxLength.
  • I have set the MaxLength to 50 and have also added a custom ErrorMessage.
  • On the Email property, I have used Required & RegularExpression, this expression will verify the email format.
  • On the FullName property, I have used Display attribute (it's not a validation attribute), and changed the name to "Full Name", it will change the label of this text box.
  • Moreover, I have also made my enums properties null-able, as you can see I have placed ? sign infrom of DeptEnum & UniEnum. ( We will see later why null-able)
  • We have added the validation attributes on our properties and now let's place a check in our Home Controllers class using builtin validation property.
Check if Data is Valid
  • So, open you HomeController.cs class placed in the Controllers Folder.
  • In HomeController class, we need to place validation check on the Registration action method of [HTTPPost] type, as this method is going to execute on pressing the Register button.
  • As you can see in above code, I have placed an IF loop and have placed a Boolean property in it called ModelState.IsValid.
  • This Boolean property will return TRUE, if there's no validation error & will return FALSE, if there's any validation error appeared.
  • So, if it's true then I have added the submitted user data and displayed it in Info link by redirecting it to Info action method and if its FALSE, then simply returned the Registration View itself.
  • One more thing to note here is that I have changed the return type of action method to IActionResult, as it contains both RedirectToAction() & View() result types.

Display Validation errors in ASP.NET Core

  • Now it's time to display validation errors on the form itself, so now open your Registration.cshtml View file.
  • Below each textbox, we need to add a <span> element, as shown in figure on right side.
  • Inside this <span> element, I have use Validation Tag Helper named asp-validation-for and this Tag Helper is taking Username as a value.
  • So, if there's any validation error appeared for Username, then it will be displayed here.
  • Let's add this <span> element below all the textboxes, as shown in below figure:
  • You can see in above figure, that I have placed <span> element containing asp-validation-for Tag Helper, below every input field.
  • One more thing to note here is that I have added an option element Please Select, in both of my <select> tags, I have encircled them in above figure.
  • Now let's run our application, and without entering any data, hit the Register button, and we will get validation errors, as shown in below figure:
  • You can see in above figure that we are getting the Validation Error Messages for each component and at the end we have the summary of Validation errors.
  • Moreover, for our Select boxes now we have a default option "Please Select", that's why we are getting Validation Errors for them as well, as now their value is null.
  • If we select any option, then it will get value from the respective enum but in case of Please Select, its null-able and giving us Validation Error.
  • We haven't added any Bootstrap design on these elements, as I want to keep things simple for now. ( We will design them later )
So, that was all for today. I hope you have enjoyed today's lecture. In next tutorial, we will have a look at detailed introduction to Entity Framework Core. Till then take care & have fun !!!

Create a Registration Form in ASP.NET Core
Departments:
  1. Computer Engineering
  2. Computer Science
Codings:
  1. C#
Softwares:
  1. Microsoft Visual Code
  2. Microsoft Visual Studio
Hello friends, I hope you all are doing great. In today's tutorial, we will have a look at How to Create a Registration Form in ASP.NET Core. It's our 13th tutorial in ASP.NET Core series. In our previous lecture, we have seen How to use Tag Helpers in ASP.NET Core and have also discussed link, image & environment Tag Helpers. Today, we will have a look at Form Tag Helpers and with their help we will design a simple Registration Form in ASP.NET Core. It will be a quite lengthy tutorial so if you got into any trouble, then ask in comments. So, let's create our Registration Form:

Create a Registration Form in ASP.NET Core

  • Let's create a new action method named Registration, in our Home Controller class, as shown in figure on right side.
  • I have also returned a View, so let's create a new Razor View in Views > Home folder and give it a name Registration.cshtml.
  • This View is going to execute, when someone will open up this link: http://localhost:61745/home/registration
  • So, let's create our registration Form in this Registration View file, as shown in below figure:
  • It's a bit lengthy code, so let's understand this code, part by part. I have also added the Engineers.cs Code in red box for better understanding.
  • I have first used @model directive and included Engineers class in this View file, as I want this user provided data to be linked with the properties of Engineers class.
  • Next, I have given the Title for the Page which will be rendered to the Layout View file.
  • Finally, I have used the <form> tag to create my Registration Form and I have used two Tag Helpers to provide the Controller & action method.
  • So, when we will submit this form, then it will be redirected to the same page and I have also provided post method, So, this form will make a POST request, as shown in below figure:
  • Inside this form, I have created label & input and have provided a tag helper asp-for.
  • asp-for tag helper will link this input with the respective property in Engineers class.
  • As you can see, I have provided Username to my first asp-for tag helper and we also have a Username property in my engineers class.
  • Moreover, this asp-for tag helper will generate the Name & Id fields of this <input> tag, which you can check by looking at the source code of your webpage.
  • As you can see in HTML output, we have for attribute in <label> tag and in <input> tag, we have name & id attributes.
  • I have created 3 Labels & Text Boxes for their respective properties in engineers data class, i.e:
    • Username.
    • Email.
    • FullName.

Enums in ASP.NET Core

  • If you have studied C#, then you must be aware of C# Enums, so let's create two enums for our project.
  • As our site is related to Engineering, so I want the registering users to provide their University & Department Names and for that I have created enums.
  • We can place Emums anywhere in our project, so I have created a new folder in the root directory and named it TepEnums.
  • Inside this folder, I have created two enums, named as:
    • DeptEnums.
    • UniEnums.
  • Inside these Enums, I have added few data and I am going to provide this data to my select elements in registration form, these enums are shown in below figure:

Select Tag Helpers in ASP.NET Core

  • I have created 3 Textboxes at the start and then created two select element for Department & University.
  • In this <select> tag, I have used asp-items tag helper and then provided it our newly created enum DeptEnum.
  • I did the same with University <select> tag, so overall we are getting 5 values from our end user.
  • Finally, at the end of our code, we have a Register button.
  • Moreover, I have also changed the data type of University & Department from string to their respective enum, shown in the first figure of this tutorial.

Import Namespaces in Layout Imports File

  • We have to include the namespaces of our enums in the Imports Layout File, so that we could use them in all of our Views.
  • Similarly, as we are linking for Registration form with engineers class, which is present in Models folder, so we also have to include this Models Namespace, as shown in below figure:
  • We have made all the changes and now it's time to run our web application and if everything goes fine, then you will get similar results:
  • So, we have created our registration form but if you click on this Register Button, then it won't do anything except refreshing the page.
Create Method for adding New User
  • We have created the font-end View for this registration form and have also created its action Method in Controller, but we haven't yet created it's model's function.
  • So, let's open the IEngineersRepository.cs file in Models Folder and create a method in it for Adding New Engineer, using data coming from registration form, as show in figure on right side.
  • We have declared the method in interface, so we have to provide its implementation as well in the EngineersRepository class, which is implementing this interface.
  • So, open your EngineersRepository.cs file and inside this file, I have provided the implementation of AddNewEngineer() function.
  • This function takes engineer as an input, which we will send it from Controllers class and when it gets this new engineers data, then we need to increment the id property, which has to be set internally.
  • After that, I am adding this engineer variable in my _EngineersData array and finally returning the newly created engineer variable.
  • So, we have successfully added the Model method for our Registration form, and when it will get the data, it will simply save it in the EngineerData array. ( We will save data in database in our coming lectures )

POST action method in ASP.NET Core

  • Now open your HomeController.cs file, whcih has the action method Registration.
  • This action method was used to open the Registration View but what will happen, when we press the Register button.
  • When we press the REgister button, then HTML form will make a POST request so, let's create two method with same name i.e. Registration.
  • First method will handle the HTTP Get request i.e. will simply display the Registration Form.
  • Second method will handle the HTTP POST request and will execute on Register Button press, as shown in below figure:
  • You can see in above figure, I have placed an [HTTPGet] attribute before first action method and thus it will simply serve the respective View file.
  • While, I have placed [HTTPPost] attribute before second method and thus when we press the Register Button, a POST request will be generated and thus this action method will execute.
  • In this Post method, I have simply executed the AddNewEngineer method of Model class, which will add this new engineer.
  • Finally, I have redirected it to Info Page and have shown the details of newly created user.
  • Now when you run your project, and add users' data using registration form then it's info page will open up with new engineer's data.
  • I haven't added any Bootstrap code yet, as I want to keep things simple, we will design our application in future lectures.
So, that was all for today. So far, we haven't placed any validation check on our submitted data, we will do that in our next lecture. Till then take care & have fun !!!

HTML Tag Helpers in ASP.NET Core
Departments:
  1. Computer Engineering
  2. Computer Science
Codings:
  1. C#
Softwares:
  1. Microsoft Visual Code
  2. Microsoft Visual Studio
Hello friends, I hope you all are doing great. In today's lecture, we will have a look at HTML Tag Helpers in ASP.NET Core. It's our 12th tutorial in ASP.NET Core series. If you have worked on ASP.NET then you must have been familiar with HTML Helpers. Tag Helpers are quite similar to HTML Helpers with slightest difference in its syntax. Tag Helpers are new in ASP.NET Core and were not part of ASP.NET. So, let's first understand what are Tag Helpers & why we need to use them and at the end we will also discuss few common tag helpers in detail. So, let's get started with HTML Tag Helpers in ASP.NET Core:

HTML Tag Helpers in ASP.NET Core

  • HTML Tag Helpers in ASP.NET Core are server side components and thus executed on the server to create HTML elements of the webpage.
  • ASP.NET Core has a lot of built-in Tag Helpers for links, images, forms etc. available in Microsoft.AspNetCore.Mvc.TagHelpers assembly and we need to use @AddTagHelper directive to include them in Views.
  • As we want to use these Tag Helpers in all of our Razor Views, so I am going to include this TagHelper assembly in _ViewImports.cshtml file, which we have created in 10th lecture and has all the assemblies importing statements.
  • AS you can see in the figure on right side, I have imported Tag Helper assembly using @AddTagHelper directive and it has two parameters.
  • I have added * in first parameter, which means I want to import all the Tag Helpers available in TagHelper assembly.
So, after adding this statement, we can now use Tag Helpers in our project. Let's have a look at few commonly used Tag Helpers:

HTML Tag Helpers for Hyperlinks

  • In our Bootstrap lecture, we have added three <a> elements in our Info View file but haven't provided the href value.
  • So, now let's use Tag Helpers to provide link value for href parameter of <a> tag, as shown in below figure:
  • I have marked these 3 links with red box and you can see that I have used 3 link Tag Helpers i.e.
    • asp-controller: I have provided the controllers name i.e. home.
    • asp-action: I have provided the action method name i.e. Index for first link & Info for second.
    • asp-route-id: I have provided the third parameter in it, while id is the name of the parameter.
  • All Tag Helpers start with asp- prefix and are embedded in HTML tags as simple parameters.
  • Now let's run this app and open this Info link and have a look at the HTML source, as shown in the below figure:
  • I have encircled the output links with green box and you can see that we don't have any tag helpers in our output file.
  • Instead, these tag helpers generated the HTML code of href parameter and we can see that the first link is of Homepage and the second link is of /Home/Info/3.
  • Now, you must be wondering that why we need to use Tag Helpers, as we can easily add the hard coded links.
  • The main benefit is, in future if you change your Controllers' names then your links will be changed and if you have placed them hard coded then you have to manually change them one by one.
  • But with Tag Helpers, there's no need to change as they will get the update name of Controller or action method and will provide the corrected link.
  • Moreover, Tag Helpers are inline with HTML unlike HTML Helpers and are thus easy to use.

HTML Tag Helper for Images

  • If we change any existing image on our server without changing its link, the browser will keep on showing the old image, because of Browser Cache.
  • So, in order to avoid that we need to use a builtin HTML Tag Helper called asp-append-version in <img> tag, as shown in below figure:
  • So, now if the image content is changed on the server then it will make the new image available to the end user.
  • If you check the HTML code of your output page, then you will find a unique string appended to your image link, which is calculated using the image content.
  • So, if image content is changed then this string will also be calculated again and thus browser will know that there's new content in the image and will load it again from the server, instead of providing it from its cache.

HTML Tag Helper for Environments

  • Using Environment Tag Helper, we can execute different content of the webpage, based on application environment.
  • We have studied Environment variable in 5th lecture and have seen that we set this variable in lauchSettings.json file.
  • In our Development Environment, we need to use non-minified versions of all of our third part client side libraries i.e. Bootstrap, Jquery, Javascript etc.
  • But in Staging or Production Environment, we should use minified versions and for better performance, we should get them from their CDN networks.
  • So, let's make these changes using Tag Helpers, open your _Layout.cshtml file, placed in Views > Shared folder.
  • We have linked Bootstrap file with our project here, so let's add some code in it, as shown in below figure:
  • You can see in above figure that in green box, I have placed the link to non-minified version of Bootstrap inside Environment tag helper and I have included Development Environment.
  • So, this link will be used only when we are working in Development Environment.
  • In the red box, I have excluded Development Environment, so this block will work for all Environments except Development.
  • Inside this block, I have placed the Bootstrap CDN link, which you can get from its official site.
  • But what if, this external CDN is link is down for some reason, then your server won't be able to fetch those files and thus your site won't work perfectly.
  • In such cases, we should fall back to our own server and get the minified version of Bootstrap.
  • So, let's add few more Tag Helpers to achieve that, as shown in below figure:
  • As you can see in above figure, I have added five tag helpers in <link> tag.
  • So if our application is unable to get the CDN link, then it will fallback to our own server & get the minified version of Bootstrap.
  • These tag helpers are injecting a JavaScript code to check, whether we got the CDN link or not.
  • As we have added this code in our Razor Layout file so it will be applied to all of our Views. ( We will add more Views in coming lectures )
So, that was all for today. I hope you have enjoyed today's lecture. In next tutorial, we will have a look at How to design Bootstrap navigation Menu in ASP.NET Core. Till then take care & have fun !!!

How to include Bootstrap in ASP.NET Core
Departments:
  1. Computer Engineering
  2. Computer Science
Codings:
  1. C#
Softwares:
  1. Microsoft Visual Code
  2. Microsoft Visual Studio
Hello friends, I hope you all are doing great. In today's tutorial, we will have a look at How to include & use Bootstrap in ASP.NET Core. It's our 12th tutorial in ASP.NET Core series. As it's ASP.NET Core tutorial so I am not going to explain bootstrap much. But you must have the basic idea of Bootstrap, its a client side package of CSS libraries, designed by twitter and these days you can't design a responsive site with Bootstrap as it follows symmetry and is too easy to use. So, let's get started with How to include Bootstrap in ASP.NET Core:

How to include Bootstrap in ASP.NET Core

  • There are many third party tools ( Bower, NPM, WebPack etc. ) available in Visual Studio for installing client side applications like Bootstrap, JavaScript, Jquery etc.
  • But we are going to use builtin tool of Visual Studio called LibMan ( short for Library Manager ), for installing third party packages, we can use both file system & CDN.
  • LibMan is a light-weight client side library acquisition tool, which not only downloads the third party libraries but also keep a track in a special file.
  • In order to open Library manager, right click on your project's name in Solution Explorer & then Add > Client Side Library and below dialog box will open up:
  • You can see in above figure that I have made a search for twitter-bootstrap@4.3.1 in the Library Text Box and LibMan previewed its files.
  • After that I have changed the Target Location and its now wwwroot/lib/bootstrap, so my bootstrap files will be placed inside lib folder of wwwroot folder.
  • After these settings click the Install button and these bootstrap files will be installed.
  • Let's also install jquery using Library manager, as shown in below figure:
  • Library Manager has also created LibMan.json file which keeps the record of all the third party packages installation.
  • I have placed both bootstrap & jquery in wwwroot > lib folder, as shown in below figure:
  • That's how, we can easily install third party client side packages in ASP.NET Core.
  • Now, we need to include this Bootstrap file in our Razor Layout View file, as shown in below figure:
  • You can simply drag & drop the bootstrap file in this Layout file and the link tag will automatically be generated.
  • So, now let's add some bootstrap code in our Info View file to make it look eye caching, as shown in below figure:
  • Now run your application and navigate to info page and if everything goes fine then you will get similar results, as shown in below figure:
  • Now you can see our page got a much nicer look with bootstrap included.
So, that was all about bootstrap in ASP.NET Core. I hope you have enjoyed today's lecture. In the next tutorial, we will have a look at Tag Helpers in ASP.NET Core. Till then take care & have fun !!!

URL Routing in ASP.NET Core
Departments:
  1. Computer Engineering
  2. Computer Science
Codings:
  1. C#
Softwares:
  1. Microsoft Visual Code
  2. Microsoft Visual Studio
Hello friends, I hope you all are doing great. In today's tutorial, we will have a look at URL Routing in ASP.NET Core. It's our 11th tutorial in ASP.NET Core series and it's an important but quite easy concept to understand. You must be wondering how we are routing rite now as we haven't added any routing codes yet. But if you remember, we have used MVC with default route middleware in our pipeline and this middleware automatically sets up this default URL routing for our web application.  So, let's understand how this URL Routing works in ASP.NET Core:

URL Routing in ASP.NET Core

  • URL Routing in ASP.NET Core is used to provide the controller's action method to the incoming HTTP request.
  • In simple words, when a user enters an HTTP URL in its browser, then it is greeted by the respective controller's method and which controller's method should by executed, it is decided by the URL Routing.
  • As you can see in below figure that our controller class has two action methods in it i.e. Index & info:
  • By default, first segment of URL ( home in our case ) is the name of the Controller and the second segment is the name of the action method. So, when we have info in the second segment then Info action method will be executed.
  • So, now let's understand this third segment in URL link, which is routed as a parameter to the action method.
  • If you remember, when we created the Info action method then we have hard coded the value of Engineers to 1.
  • So, let's make it flexible and ask the user to enter it as a third segment in the URL.
  • Open your Controller's file and make these changes to Info action method, as shown in figure on right side.
  • I have added a parameter int id in our Info method and then placed this id in the GetEngineers function.
  • So, now run your function and navigate to /home/info/3 and now you will get the data of your third engineer, as shown in below figure:
  • Now, we have automated our Info method by adding this third parameter and we can view any engineer's data quite easily.
  • But, if you open /home/info/ without the third parameter, then you will get a run time error and one way to avoid it is by making this third parameter null-able, as shown in figure on right side.
  • I have made the id null-able and then assigned it a default value of 1 by using id??1.
  • So, now if you don't add the third parameter then it will show you the data of first engineer by default.
  • This default routing of ASP.NET Core is also called Conventional Routing.
I hope you have understood the Conventional URL Routing in ASP.NET Core, so that was all for today. In the next lecture, we will have a look at How to include Bootstrap in ASP.NET Core. Till then take care & have fun !!!

Razor Layout Views in ASP.NET Core
Departments:
  1. Computer Engineering
  2. Computer Science
Codings:
  1. C#
Softwares:
  1. Microsoft Visual Code
  2. Microsoft Visual Studio
Hello friends, I hope you all are doing great. In today's tutorial, we will have a look at different Razor Layout Views in ASP.NET Core. It's our 10th tutorial in ASP.NET Core series. You must have noticed in websites that they have common sections, which remains the same throughout the website i.e. Header Section, Footer Section, Sidebar etc. In today's lecture, we will have a look at how to design these default layouts of a website. We have already discussed the MVC architecture in detail so now it's time to start building our site's layout or basic structure. Today we will just discuss different files available in ASP.NET Core for default layout designing. So, let's get started with Layout View in ASP.NET Core:

Razor Layout View in ASP.NET Core

  • Razor Layout View in ASP.NET Core is a Razor file ( extension .cshtml ), used to design default Layouts of the website, which are then embedded in all ( or desired ) Views of the website.
  • A simple website's layout is shown in the figure on right side and these are normal sections of a blog and depending on site, these sections may increase or decrease.
  • Moreover, you may have more than 1 Layout for a single View i.e. different layouts for signed in users and guest users.
  • We place these Layout Views in Shared sub folder of Views folder, so let's create this Shared Folder inside Views folder and then click on Add > New item.
  • Add New Item dialog box will open up, make a search for razor in it, as shown in below figure:
  • We have already used Razor View to create Info View Page and we have seen that in razor files, we can use both html and C#, these are like smart HTML Pages.
  • So, today we will have a look at remaining Razor files and first let's add this Razor Layout file in our Views > Shared folder.
  • You must have noticed the underline sign ( _ ) before Layout name, its a convention ( not necessary ) to differentiate Layout files from other files, although you can write any name you want.

Why use Razor Layout View ?

  • It reduces repetition of code thus saves time especially in bigger projects.
  • Let's say you are working on a blog then you have to place these Footers, Headers & Sidebars etc and if you hard code them in each of your page then editing will be a serious issue.
  • That's why it's better to have all the default settings of our Views in a single file, so that we could change them easily.
  • Layouts are also used for consistent look and behavior of the website across all its webpages, you can think of them as HTML theme of your web application.
  • These Layout files are the alternative of Master Pages in ASP.NET Web Forms.
So, let's add some code in our newly created Layout View File:

Adding code in Razor Layout View file

  • We have added the Razor Layout file in our Views > Shared folder, open this file and you will find HTML code in it, as shown in the figure on right side.
  • As you can see this code is kind of an HTML wrapper having all the required tags i.e. head, body, meta, title etc. but it doesn't have any content in it.
  • It has 2 C# code lines in it:
    • First one is Title property which will set the title of the page.
    • Second one is RenderBody() method, View specific content will be injected here.
  • Both of these C# lines will be getting data from the View, which will be calling this razor layout.
  • Now, let's open our Info View file, and delete the wrapping HTML code, as shown in figure on right side.
  • Now, I just have the content HTML code in my Info View file.
  • Now let's enable this Info View file to use Razor Layout file and for that we have to include a new razor code block in our View file.

Layout Property in Razor View file

  • You can see in figure on right side that I have added a new razor code block at the top of my Info View File.
  • In this razor code block, I have specified two properties:
    • First one is the Layout property, where I have provided the path to the Razor Layout File.
    • Second one is ViewBag.Title, which was also present in Layout file and this property will set the Title of the Page.
  • Now run your web application and obviously you won't find any difference and if you check the Page soruce of Info page then you will find the complete html code in it with all required tags i.e. head, body, title etc.
Now let's have a look at another property called Sections in Razor Layout Files:

Render Sections in Razor Layout Files

  • Sections is a property in Razor Layout Files, which is used for the organized placement of few page elements.
  • You must have seen any movie review site, normally in such reviews, the review box is placed right at the top in either left or right corner displaying the overall review aggregate.
  • Sections are used to place such sticky elements in web pages, I have placed a Render section in my _Layout.cshtml file named AdBanner.
  • First I have placed an IF loop to check if the section is present in the View or not and if it's present then execute that section.
  • This IF statement is necessary as it makes the section optional otherwise it will be mandatory and if you don't have it in your View file then you will get a run time error.
  • So, this Ad Banner section will be placed at the end of the webpage.
  • Now, we need to create this AdBanner section in our Info View File, so open your View file and place the code as shown in figure on right side.
  • You can see I have used @section directive and then provided it the same name as in our Layout file and then in curly brackets { } placed the content ( which doesn't make much sense for now ).
  • Now run your project and open this link home/info and if everything goes fine then you will see this line at the end of your file, as shown in below figure:
  • So, despite the fact that we have placed the section at the top of our Razor View File but still it appeared at the bottom, as specified in the Razor Layout File.
  • We can create as many sections as we want in our Razor Layout file.
You must have noticed that we have to add the path of our Layout file in every View file, which is clearly a negation of DRY ( Don't Repeat Yourself ). So, let's see How to get rid of this linking.

Razor View Start File in ASP.NET Core

  • Razor View Start File in ASP.NET Core is used to specify the Razor Layout file location for Razor View Files.
  • It is normally placed inside the Views folder, so let's Add New item and in the search dialog box, make a search for razor, as shown in belwo figure:
  • Previously, we have selected Razor Layout file and this time we are going to select Razor View Start file and you can see it also has underscore sign ( _ ) at the start of the name.
  • Add this file to your project and you will find a simple code in it, as shown in figure on right side.
  • This code is automatically generated by visual studio, as it knows we have the Layout file in our project, so now we have successfully specified the Layout file for our View files.
  • So, now remove your path from the Info View file and run your project and it will still work the same.
  • It's really helpful as if you wanna change the name or path of your Layout file then you can quite easily do it here and it will be applicable to your entire application.
  • Moreover, Razor View Start file is hierarchical i.e. you can add View Start files in each folder and it will override the parent View Start settings.
  • So, if you wanna assign different Layouts to different Controllers then you can easily do that by adding a new View Start file in these folders.
  • We can still specify path to Layout file directly in View file and it will override everything, we can also make Layout = "null", which will remove all the Layouts from that View.
  • So, the Razor View Start file reduces the code redundancy and thus increases maintainability.
Finally, let's have a look at the Razor View Imports file, which is the last one in razor files import section:

Razor View Imports in ASP.NET Core

  • Razor View Imports in ASP.NET Core are used to include common namespaces, required by the Razor View files.
  • In our Info View file, you have seen that we have specified @model directive at the top and then provided fully qualified name of our View Model, which in our case is:

TheEngineeringProjects.ViewModels.HomeInfoViewModel

  • So, if we have to add more View Models or simple Models then we have to write full name again, which is again a violation of DRY, so it's always a better approach to place most commonly used namespaces in our Razor View Imports file.
  • This file is placed inside Views folder and is hierarchical ( similar to View Starts ).
  • So, right click on Views folder and then Add > New Item and select Razor View Imports file, it's name also starts with underscore sign ( _ ).
  • Inside this file, place this single line of code, as shown in the figure on right side.
  • Here, I have placed @using directive and then specified the namespace if my ViewModels folder and it will be automatically included in my View files.
  • So, now open your Info View File and remove this namespace from @model directive and now we will just specify the name of the ViewModel, which we are using for the View, as shown in below figure:
  • So, that's our final Info View Code and you can see that now we don't have any code repeatability in it.
  • The code is clean and contains only the content of this View file, so our project is more organized and maintained, although have no effect on the output.
So, that was all for today. I hope you have enjoyed today's lecture, it was quite a lengthy one but you must have got the idea how important it is. In the next lecture, we will have a look at Routing in ASP.NET Core. Till then take care & have fun !!!

ViewModels in ASP.NET Core
Departments:
  1. Computer Engineering
  2. Computer Science
Codings:
  1. C#
Softwares:
  1. Microsoft Visual Code
  2. Microsoft Visual Studio
Hello friends, I hope you all are doing great. In today's tutorial, we will have a look at How to Create ViewModels in ASP.NET Core. It's our 9th tutorial in ASP.Net Core series. We have already covered Controllers, Models & Views in our previous lectures and now it's time to understand this fourth pillar of MVC architecture. ViewModel is not an integral part of MVC architecture and can be ignored in simple projects but in complex applications, we have to use ViewModel as it adds flexibility in the project. So, let's have a look at ViewModels in ASP.NET Core:

ViewModels in ASP.NET Core

  • ViewModels in ASP.NET Core ( also called Data Transfer Objects [DTO] ) are used to send Models data from Controller to View.
  • Normally in complex cloud based applications, data from multiple Model classes needs to be displayed in a single View file, in such cases it's wise to first combine all the incoming data in a single ViewModel file and then attach this ViewModel class with respective View.
  • We can place ViewModels anywhere in our project but to keep the project files organized, it's better to place all ViewModel files in a folder named ViewModels, as shown in the figure on right side.
  • Inside this ViewModel folder, I have added a new C# file and named it HomeInfoViewModel.cs as this ViewModel is for Info action method of Home Controller, its a convention to place ViewModel at the end of the filename.
  • Inside this ViewModel class, I have just added two properties, ViewModel code is shown in the figure on right side.
  • You can see in the code that first property is of type Engineers, which is from our Model Class Engineers.
  • While the second property is just a string for Page Title, if you remember in the last lecture, we have hard coded the Page Title in our View file.
Edit Home Controller File
  • Now open your HomeController.cs file and in the Info action method, add this code shown in figure on right side.
  • In Info action method, I have created a new instance of this ViewModel and have provided values for its properties i.e. first Engineer data & Page Title.
  • Finally I have passed this ViewModel object to respective View.
  • You must be wondering why we need to create this new file and have added extra code, it seems lengthy with single Model data but when you are working with 10 or 20 Models and you have to display their data in single View file, then ViewModels prove really helpful.
Update Info View File
  • Finally, we need to update our Info.cshtml View file according to this new ViewModel.
  • Code is shown in the figure and you can see that now I am using @model directive for ViewModel class now.
  • Moreover, I am now using properties of that ViewModel using @Model and now we just have the HTML code and rest is coming from C#, thus making it more flexible.
  • Now if you run your project, you will get the same results as in our previous lecture, but now the project is more organized and easily readable, here's the output:
So, that was all about ViewModels in ASP.NET Core. I hope you have enjoyed today's tutorial and if you have any questions, please ask in comments. Have fun !!!
Syed Zain Nasir

I am Syed Zain Nasir, the founder of <a href=https://www.TheEngineeringProjects.com/>The Engineering Projects</a> (TEP). I am a programmer since 2009 before that I just search things, make small projects and now I am sharing my knowledge through this platform.I also work as a freelancer and did many projects related to programming and electrical circuitry. <a href=https://plus.google.com/+SyedZainNasir/>My Google Profile+</a>

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Syed Zain Nasir
2 days ago