Skip to main content

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

Popular posts from this blog

Blazor WebAssembly Custom Authentication From Scratch

In this article, we are going to explore and implement custom authentication from the scratch. In this sample, we will use JWT authentication for user authentication. Main Building Blocks Of Blazor WebAssembly Authentication: The core concepts of blazor webassembly authentication are: AuthenticationStateProvider Service AuthorizeView Component Task<AuthenticationState> Cascading Property CascadingAuthenticationState Component AuthorizeRouteView Component AuthenticationStateProvider Service - this provider holds the authentication information about the login user. The 'GetAuthenticationStateAsync()' method in the Authentication state provider returns user AuthenticationState. The 'NotifyAuthenticationStateChaged()' to notify the latest user information within the components which using this AuthenticationStateProvider. AuthorizeView Component - displays different content depending on the user authorization state. This component uses the AuthenticationStateProvider

How Response Caching Works In Asp.Net Core

What Is Response Caching?: Response Caching means storing of response output and using stored response until it's under it's the expiration time. Response Caching approach cuts down some requests to the server and also reduces some workload on the server. Response Caching Headers: Response Caching carried out by the few Http based headers information between client and server. Main Response Caching Headers are like below Cache-Control Pragma Vary Cache-Control Header: Cache-Control header is the main header type for the response caching. Cache-Control will be decorated with the following directives. public - this directive indicates any cache may store the response. private - this directive allows to store response with respect to a single user and can't be stored with shared cache stores. max-age - this directive represents a time to hold a response in the cache. no-cache - this directive represents no storing of response and always fetch the fr

.Net5 Web API Managing Files Using Azure Blob Storage

In this article, we are going to understand the different file operations like uploading, reading, downloading, and deleting in .Net5 Web API application using Azure Blob Storage. Azure Blob Storage: Azure blob storage is Microsoft cloud storage. Blob storage can store a massive amount of file data as unstructured data. The unstructured data means not belong to any specific type, which means text or binary data. So something like images or pdf or videos to store in the cloud, then the most recommended is to use the blob store. The key component to creating azure blob storage resource: Storage Account:- A Storage account gives a unique namespace in Azure for all the data we will save. Every object that we store in Azure Storage has an address. The address is nothing but the unique name of our Storage Account name. The combination of the account name and the Azure Storage blob endpoint forms the base address for each object in our Storage account. For example, if our Storage Account is n

.Net5 Web API Redis Cache Using StackExchange.Redis.Extensions.AspNetCore Library

In this article, we are going to explore the integration of Redis cache in .Net5 Web API application using the 'StackExchange.Redis.Exntensions' library. Note:- Microsoft has introduced an 'IDistributedCache' interface in dotnet core which supports different cache stores like In-Memory, Redis, NCache, etc. It is simple and easy to work with  'IDistributedCache', for the Redis store with limited features but if we want more features of the Redis store we can choose to use 'StackExchange.Redis.Extensions'.  Click here for Redis Cache Integration Using IDistributedCache Interface . Overview On StackExchange.Redis.Extnesions Library: The 'StackExchange.Redis.Extension' library extended from the main library 'StackExchange.Redis'. Some of the key features of this library like: Default serialization and deserialization. Easy to save and fetch complex objects. Search key. Multiple Database Access Setup Redis Docker Instance: For this sampl

Endpoint Routing In Asp.Net Core

How Routing Works In  Core 2.1 And Below Versions?: In Asp.Net Core routing is configured using app.UseRouter() or app.UseMvc() middleware. app.UseMvc(routes => { routes.MapRoute( name: "default", template: "{controller=Home}/{action=Index}/{id?}"); }); Here in Dotnet Core version 2.1 or below versions on the execution of route middleware request will be navigated appropriate controller matched to the route. An operation or functionality which is dependent on route URL or route values and that need to be implemented before the execution of route middleware can be done by accessing the route path from the current request context as below app.Use(async (context, next) => { if(context.Request.Path.Value.IndexOf("oldvehicle") != -1) { context.Response.Redirect("vehicle"); } else { await next(); } }); app.UseMvc(routes => { routes.MapRoute( name: "vehicleRoute", template: "vehicle", defaul

Asp.Net Core MVC Form Validation Techniques

Introduction: Form validations in any applications are like assures that a valid data is storing on servers. All programing frameworks have their own individual implementations for form validations. In Dotnet Core MVC application server-side validations carried on by the models with the help of Data Annotations and the client-side validations carried by the plugin jQuery Unobtrusive Validation. jQuery Unobtrusive Validation is a custom library developed by Microsoft based on the popular library  jQuery Validate . In this article, we are going to learn how the model validation and client-side validation works in Asp.Net Core MVC Application with sample examples. Getting Started: Let's create an Asp.Net Core MVC application project using preferred editors like Microsoft Visual Studio or Microsoft Visual Studio Code. Here I'm using Visual Studio. Let's create an MVC controller and name it as 'PersonController.cs' and add an action method as bel

NestJS File Upload

In this article, we are going to understand the steps to create a file uploading endpoint in the NestJS application. Key Features In NestJS File Upload: Let us know some key features of NestJS file upload before implementing a sample application. FileInterceptor: The 'FileInterceptor' will be decorated on top of the file upload endpoint. This interceptor will read single file data from the form posted to the endpoint. export declare function FilesInterceptor(fieldName: string, localOptions?: MulterOptions): Type<NestInterceptor>; Here we can observe the 'fieldName' first input parameter this value should be a match with our 'name' attribute value on the form file input field. So our interceptor read our files that are attached to the file input field. Another input parameter of 'MulterOptions' that provides configuration like file destination path, customizing file name, etc. FilesInterceptor: The 'FilesInterceptor' will be decorated on t

.NET Core MVC Application File Upload To Physical Location With Buffered Technique

Buffering Technique In File Upload: The server will use its Memory(RAM) or Disk Storage to save the files on receiving a file upload request from the client.  Usage of Memory(RAM) or Disk depends on the number of file requests and the size of the file.  Any single buffered file exceeding 64KB is moved from Memory to a temp file on disk.  If an application receives heavy traffic of uploading files there might be a chance of out of Disk or RAM memory which leads to crash application. So this Buffer technique used for small files uploading. In the following article, we create a sample for the file uploading using .NET Core MVC application. Create The .NET Core MVC Project: Let's create a .NET Core MVC project, here for this sample I'm using Visual Studio Code as below.   Check the link to use the Visual Studio Code for .NET Core Application . IFormFile: Microsoft.AspNetCore.Http.IFormFile used for file upload with buffered technique. On uploading files f

Ionic Picker Sample Code In Angular

Introduction: Ionic Picker(ion-picker) is a popup slides up from the bottom of the device screen, which contains rows with selectable column separated items. The main building block of ion-picker as follows: PickerController PickerOptions PickerController: PickerController object helps in creating an ion-picker overlay. create(opts?: Opts): Promise<Overlay> PickerController create method helps in create the picker overlay with the picker options PickerOptions: PickerOptions is a configuration object used by PickerController to display ion-picker. Single Column Ionic Picker: single.item.picker.ts: import { Component } from "@angular/core"; import { PickerController } from "@ionic/angular"; import { PickerOptions } from "@ionic/core"; @Component({ selector: "single-column-picker", templateUrl:"single.item.picker.html" }) export class SingleItemPicker { animals: string[] = ["Tiger&quo

.Net Core HttpClient JSON Extension Methods Using System.Net.Http.Json Package

.Net Core 3.0 onwards Microsoft brought up a new package called System.Net.Http.Json. This new package provides JSON extension methods for HttpClient. These JSON extension methods will have a prebuild mechanism for serializing or deserializing response data or payload of HttpClient call. System.Net.Http.Json extension methods that are provided to HttpClient, few of them are mentioned below. GetFromJsonAsync PostAsJsonAsync PutAsJsonAsync ReadFromJsonAsync In this article, we understand System.Net.Http.Json package by implementing the HttpClient samples by with and without JSON extension methods and compare them. Create A .Net Core Web API Sample Application: Let's create a .Net Core sample Web API application, from this application we will consume another Web API by implementing HttpClient calls. We can create a Web API sample application using IDE like Visual Studio 2019(Supports .Net Core 3.0 plus) or  Visual Studio Code . Create A Typed Client: In .Net Core using the Http