Introduction To Blazor Components

Introduction:

A Page or Form or Dialog is used to construct a Blazor Application are made of Components. A Component is a block of code consist of C# + HTML + CSS. Components give the advantage of code splitting, nesting, and reusability.

In this journey, we are going to explore Blazor components with sample examples.

Blazor Or Razor Component:

Blazor components can be called Razor Components because they implemented in a Razor file(.razor). In general, the component is a combination of C# @code block and Html UI of Razor syntax.

A simple component with c# code and Html as below:

Pages/Parent.razor:

<h3>Hey I'm Parent Component</h3>

@code {

}

Component Naming Convention:

Blazor Components should always start with a capital letter. Trying to create a component name with a small casing letter leads to a compilation error.

Example create a component as 'Pages/parent.razor' result error as below

@code block:

C# @code block is like a class where we can declare properties and methods. It also contains Life-Cycle methods of the component in addition to the user-defined logical serving methods.

@code {
    public string Heading => "Hey I'm Parent Component";

    public void DoSomething()
    {
        // method serves user logic
    }

    protected override Task OnInitializedAsync()
    {
        // Blazor component life-cycle method
        return base.OnInitializedAsync();
    }
}

Multiple @code block:

Yes, it possible to use multiple @code blocks. It doesn't mean we can create duplicate methods or properties with the same names in different @code blocks, such implementation will give compilation errors. Because of razor file compiled to a partial class where classes won't allow parameters or methods with the same name.

Pages/Parent.razor(Html Portion):

<h3>@FirstBlock</h3>
<h3>@SecondBlock</h3>

Pages/Parent.razor(@code Portion):

@code {
    public string FirstBlock => "Hey I'm from fisrt @Code Block";
}

@code
{
    public string SecondBlock => "Hey I'm from second @code Block";
}

Rendered Output:

Code Behind File OR Partial Razor Class:

In Microsoft Web Technologies a beautiful feature to separate Html and C# code by using the code-behind file. Blazor components also support to use code-behind files. The code-behind file class must be a partial class. The Reason behind the partial class is the razor file on the compilation converted as a partial class. The code-behind file name extension "{componentName}.razor.cs".

Pages/Parent.razor:

<h3>@Heading</h3>

Pages/Parent.razor.cs(code-behind file):

public partial class Parent
{
 public string Heading => "Hey I'm from component's code behind file Parent.razor.cs";
}

Rendered Output:

Component Html Tag:

Component Html Tag is a custom Html tag whose name must match with the component file name. By default Html, Tag needs to be used with a fully qualified name for example like

{ProjectName}.Pages.{componentName} , {ProjectName}.Pages.{FolderName}.{componentName}, etc.

Pages/Index.razor:

<Blazor.Component.Test.App.Pages.Sample1.Parent></Blazor.Component.Test.App.Pages.Sample1.Parent>

Tag Name can be shortened by importing the namespace into the _Import.razor file

_Import.razor:

@using Blazor.Component.Test.App.Pages.Sample1;

Pages/Index.razor:

<Parent></Parent>

[Parameter] Attribute Or Component Parameter:

A property of component decorated with [Parameter] attribute can be called as Component Parameter. Component Parameter has the ability to take input from the HTML attribute (whose name must match the Component Parameter variable name) of component markup tag. Component Parameter access specifier should always be 'public' so that property will available for component markup tag.

Pages/Parent.razor(Html Portion):

<h3>@Heading</h3>

Pages/Parent.razor(@code Portion):

@code {
    [Parameter]
    public string Heading { get; set; }
}

Pages/Index.razor:

<Parent Heading="Hello I'm from Parent tag markup">
</Parent>

Rendered Output:

Component Data Binding OR 2-way Data Binding:

In Blazor components it is possible to do 2-way binding using '@bind' attribute which takes a c# property as its input.

Pages/Parent.razor(Html Portion):

<h3>@Heading</h3>
<input type="text"  @bind="Heading"/>

Pages/Parent.razor(@code Portion):

@code {
    public string Heading { get; set; }
}

Rendered Output:

UI Events:

Like any other front-end frameworks, Blazor also supports UI Events like click, change, focus, etc. In a component, we can register events with methods in the component. Example to register click event like @onclick="methodName".

Pages/Parent.razor(Html Portion):

<h3>Click button to increase My Rank @Count</h3>
<button type="button" class="btn btn-primary" @onclick="Increment">Click Me</button>

Pages/Parent.razor(@code Portion):

@code {
    public int Count { get; set; }

    private void Increment()
    {
        Count = Count+1;
    }
}

Rendered Output:

@ref To Access Component:

Using @ref can access the child component, public members.
@ref expects a property from the parent component and that property of type is child component type.
After components rendered the instance of child component will be assigned to the property(in the parent component) of the type child component.
Using this reference parameter we can access members of child component and modify them, but to reflect the changes we need to call "base.stateHasChanged()" in the child component.

Pages/Parent.razor(Html Portion):

<h3>Parent</h3>
<button type="button" class="btn btn-primary" @onclick="PassDataToChild">Click Me</button>
<Child @ref="child"></Child>

Pages/Parent.razor(@code Protion):

@code {
    private Child child;

    private void PassDataToChild()
    {
        child.UpdateHeading("Hi on parent button clicked my child heading changes");
    }
}

Pages/Child.razor(Html Portion):

<h3>@Heading</h3>

Pages/Child.razor(@code Portion):

@code {
    public string Heading { get; set; }

    public void UpdateHeading(string heading)
    {
        Heading = heading;
        base.StateHasChanged();
    }
}

Rendered Output:

Conditional Display Components:

Yes it possible to hide and show a component using razor sytax of "@if".

Pages/Parent.razor(Html Portion):

<h3>Parent</h3>
<button type="button" class="btn btn-primary" @onclick="ToggleChildComponent">Click Me Toggle Child Component</button>
@if (showChild)
{
  <Child ></Child>
}

Pages/Parent.razor(@code Portion):

@code {
    bool showChild = true;
    private void ToggleChildComponent()
    {
        showChild = !showChild;
    }
}

Pages/Child.razor:

<h3>I'm child Component</h3>
@code {
}

Rendered Output:

Looping Components:

Yes, it is possible to loop a component using razor "@for". On every iteration, the new component will be rendered, which are independent of components rendered in the previous iteration or next iteration.

Pages/Parent.razor:

<h3>Parent</h3>
@for (int i=0;i < 3;i++)
{
  <Child ></Child>
}
@code {

}

Pages/Child.razor:

<h3>I'm child Component</h3>
@code {
}

Rendered Output:

Wrapping Up:

Hopefully, this article gives you a basic understanding of blazor components. I will love to have your feedback, suggestions, and better techniques.

Follow Me:

Comments

Angular 14 Reactive Forms Example

In this article, we will explore the Angular(14) reactive forms with an example. Reactive Forms: Angular reactive forms support model-driven techniques to handle the form's input values. The reactive forms state is immutable, any form filed change creates a new state for the form. Reactive forms are built around observable streams, where form inputs and values are provided as streams of input values, which can be accessed synchronously. Some key notations that involve in reactive forms are like: FormControl - each input element in the form is 'FormControl'. The 'FormControl' tracks the value and validation status of form fields. FormGroup - Track the value and validate the state of the group of 'FormControl'. FormBuilder - Angular service which can be used to create the 'FormGroup' or FormControl instance quickly. Form Array - That can hold infinite form control, this helps to create dynamic forms. Create An Angular(14) Application: Let'

.NET 7 Web API CRUD Using Entity Framework Core

In this article, we are going to implement a sample .NET 7 Web API CRUD using the Entity Framework Core. Web API: Web API is a framework for building HTTP services that can be accessed from any client like browser, mobile devices, and desktop apps. In simple terminology API(Application Programming Interface) means an interface module that contains programming functions that can be requested via HTTP calls either to fetch or update data for their respective clients. Some of the Key Characteristics of API: Supports HTTP verbs like 'GET', 'POST', 'PUT', 'DELETE', etc. Supports default responses like 'XML' and 'JSON'. Also can define custom responses. Supports self-hosting or individual hosting, so that all different kinds of apps can consume it. Authentication and Authorization are easy to implement. The ideal platform to build the REST full services. Install The SQL Server And SQL Management Studio: Let's install the SQL server on our l

ReactJS(v18) JWT Authentication Using HTTP Only Cookie

In this article, we will implement the ReactJS application authentication using the HTTP-only cookie. HTTP Only Cookie: In a SPA(Single Page Application) Authentication JWT token either can be stored in browser 'LocalStorage' or in 'Cookie'. Storing the JWT token inside of the cookie then the cookie should be HTTP Only. The HTTP-ONly cookie nature is that it will be only accessible by the server application. Client apps like javascript-based apps can't access the HTTP-Only cookie. So if we use the authentication with HTTP-only JWT cookie then we no need to implement the custom logic like adding authorization header or storing token data, etc at our client application. Because once the user authenticated cookie will be automatically sent to the server by the browser on every API call. Authentication API: To authenticate our client application with JWT HTTP-only cookie, I developed a NetJS(which is a node) Mock API. Check the GitHub link and read the document on G

.NET6 Web API CRUD Operation With Entity Framework Core

In this article, we are going to do a small demo on AspNetCore 6 Web API CRUD operations. What Is Web API: Web API is a framework for building HTTP services that can be accessed from any client like browser, mobile devices, desktop apps. In simple terminology API(Application Programming Interface) means an interface module that contains a programming function that can be requested via HTTP calls to save or fetch the data for their respective clients. Some of the key characteristics of API: Supports HTTP verbs like 'GET', 'POST', 'PUT', 'DELETE', etc. Supports default responses like 'XML' and 'JSON'. Also can define custom responses. Supports self-hosting or individual hosting, so that all different kinds of apps can consume it. Authentication and Authorization are easy to implement. The ideal platform to build REST full services. Create A .NET6 Web API Application: Let's create a .Net6 Web API sample application to accomplish our

Angular 14 State Management CRUD Example With NgRx(14)

In this article, we are going to implement the Angular(14) state management CRUD example with NgRx(14) NgRx Store For State Management: In an angular application to share consistent data between multiple components, we use NgRx state management. Using NgRx state helps to avoid unwanted API calls, easy to maintain consistent data, etc. The main building blocks for the NgRx store are: Actions - NgRx actions represents event to trigger the reducers to save the data into the stores. Reducer - Reducer's pure function, which is used to create a new state on data change. Store - The store is the model or entity that holds the data. Selector - Selector to fetch the slices of data from the store to angular components. Effects - Effects deals with external network calls like API. The effect gets executed based the action performed Ngrx State Management flow: The angular component needs data for binding. So angular component calls an action that is responsible for invoking the API call. Aft

Angular 14 Crud Example

In this article, we will implement CRUD operation in the Angular 14 application. Angular: Angular is a framework that can be used to build a single-page application. Angular applications are built with components that make our code simple and clean. Angular components compose of 3 files like TypeScript File(*.ts), Html File(*.html), CSS File(*.cs) Components typescript file and HTML file support 2-way binding which means data flow is bi-directional Component typescript file listens for all HTML events from the HTML file. Create Angular(14) Application: Let's create an Angular(14) application to begin our sample. Make sure to install the Angular CLI tool into our local machine because it provides easy CLI commands to play with the angular application. Command To Install Angular CLI npm install -g @angular/cli Run the below command to create the angular application. Command To Create Angular Application ng new name_of_your_app Note: While creating the app, you will see a noti

Unit Testing Asp.NetCore Web API Using xUnit[.NET6]

In this article, we are going to write test cases to an Asp.NetCore Web API(.NET6) application using the xUnit. xUnit For .NET: The xUnit for .Net is a free, open-source, community-focused unit testing tool for .NET applications. By default .Net also provides a xUnit project template to implement test cases. Unit test cases build upon the 'AAA' formula that means 'Arrange', 'Act' and 'Assert' Arrange - Declaring variables, objects, instantiating mocks, etc. Act - Calling or invoking the method that needs to be tested. Assert - The assert ensures that code behaves as expected means yielding expected output. Create An API And Unit Test Projects: Let's create a .Net6 Web API and xUnit sample applications to accomplish our demo. We can use either Visual Studio 2022 or Visual Studio Code(using .NET CLI commands) to create any.Net6 application. For this demo, I'm using the 'Visual Studio Code'(using the .NET CLI command) editor. Create a fo

Part-1 Angular JWT Authentication Using HTTP Only Cookie[Angular V13]

In this article, we are going to implement a sample angular application authentication using HTTP only cookie that contains a JWT token. HTTP Only JWT Cookie: In a SPA(Single Page Application) Authentication JWT token either can be stored in browser 'LocalStorage' or in 'Cookie'. Storing JWT token inside of the cookie then the cookie should be HTTP Only. The HTTP-Only cookie nature is that it will be only accessible by the server application. Client apps like javascript-based apps can't access the HTTP-Only cookie. So if we use authentication with HTTP only JWT cookie then we no need to implement custom logic like adding authorization header or storing token data, etc at our client application. Because once the user authenticated cookie will be automatically sent to the server by the browser on every API call. Authentication API: To implement JWT cookie authentication we need to set up an API. For that, I had created a mock authentication API(Using the NestJS Se

ReactJS(v18) Authentication With JWT AccessToken And Refresh Token

In this article, we are going to do ReactJS(v18) application authentication using the JWT Access Token and Refresh Token. JSON Web Token(JWT): JSON Web Token is a digitally signed and secured token for user validation. The JWT is constructed with 3 important parts: Header Payload Signature Create ReactJS Application: Let's create a ReactJS application to accomplish our demo. npx create-react-app name-of-your-app Configure React Bootstrap Library: Let's install the React Bootstrap library npm install react-bootstrap bootstrap Now add the bootstrap CSS reference in 'index.js'. src/index.js: import 'bootstrap/dist/css/bootstrap.min.css' Create A React Component 'Layout': Let's add a React component like 'Layout' in 'components/shared' folders(new folders). src/components/shared/Layout.js: import Navbar from "react-bootstrap/Navbar"; import { Container } from "react-bootstrap"; import Nav from "react-boot

A Small Guide On NestJS Queues

NestJS Application Queues helps to deal with application scaling and performance challenges. When To Use Queues?: API request that mostly involves in time taking operations like CPU bound operation, doing them synchronously which will result in thread blocking. So to avoid these issues, it is an appropriate way to make the CPU-bound operation separate background job. In nestjs one of the best solutions for these kinds of tasks is to implement the Queues. For queueing mechanism in the nestjs application most recommended library is '@nestjs/bull'(Bull is nodejs queue library). The 'Bull' depends on Redis cache for data storage like a job. So in this queueing technique, we will create services like 'Producer' and 'Consumer'. The 'Producer' is used to push our jobs into the Redis stores. The consumer will read those jobs(eg: CPU Bound Operations) and process them. So by using this queues technique user requests processed very fastly because actually

Tech Seeker

Search This Blog