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# Blazor
Blazor apps are based on *components* . A **component** in Blazor is an element of UI, such as a page, dialog, or data entry form.
Components are .NET C# classes built into .NET assemblies that:
- Define flexible UI rendering logic.
- Handle user events.
- Can be nested and reused.
- Can be shared and distributed as Razor class libraries or NuGet packages.
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The component class is usually written in the form of a Razor markup page with a `.razor` file extension. Components in Blazor are formally referred to as *Razor components* .
## Project Structure & Important Files
### Blazor Server Project Stucture
```txt
Project
|-Properties
| |- launchSettings.json
|
|-wwwroot --> static files
| |-css
| | |- site.css
| | |- bootstrap
| |
| |- favicon.ico
|
|-Pages
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| |- _Host.cshtml --> fallback page
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| |- Component.razor
| |- Index.razor
| |- ...
|
|-Shared
| |- MainLayout.razor
| |- MainLayout.razor.css
| |- ...
|
|- _Imports.razor --> @using imports
|- App.razor --> component root of the app
|
|- appsettings.json --> application settings
|- Program.cs --> App entrypoint
|- Startup.cs --> services and middleware configs
```
### Blazor WASM Project Structure
```txt
Project
|-Properties
| |- launchSettings.json
|
|-wwwroot --> static files
| |-css
| | |- site.css
| | |- bootstrap
| |
| |- index.html
| |- favicon.ico
|
|-Pages
| |- Component.razor
| |- Index.razor
| |- ...
|
|-Shared
| |- MainLayout.razor
| |- MainLayout.razor.css
| |- ...
|
|- _Imports.razor --> @using imports
|- App.razor --> component root of the app
|
|- appsettings.json --> application settings
|- Program.cs --> App entrypoint
```
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### Blazor PWA Project Structure
```txt
Project
|-Properties
| |- launchSettings.json
|
|-wwwroot --> static files
| |-css
| | |- site.css
| | |- bootstrap
| |
| |- index.html
| |- favicon.ico
| |- manifest.json
| |- service-worker.js
| |- icon-512.png
|
|-Pages
| |- Component.razor
| |- Index.razor
| |- ...
|
|-Shared
| |- MainLayout.razor
| |- MainLayout.razor.css
| |- ...
|
|- _Imports.razor --> @using imports
|- App.razor --> component root of the app
|
|- appsettings.json --> application settings
|- Program.cs --> App entrypoint
```
### `manifest.json`, `service-worker.js` (Blazor PWA)
[PWA ](https://web.dev/progressive-web-apps/ )
[PWA MDN Docs ](https://developer.mozilla.org/en-US/docs/Web/Progressive_web_apps )
[PWA Manifest ](https://developer.mozilla.org/en-US/docs/Web/Manifest )
[Service Worker API ](https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API )
```json
// manifest.json
{
"name": "< App Name > ",
"short_name": "< Short App Name > ",
"start_url": "./",
"display": "standalone",
"background_color": "#ffffff ",
"theme_color": "#03173d ",
"icons": [
{
"src": "icon-512.png",
"type": "image/png",
"sizes": "512x512"
}
]
}
```
## Common Blazor Files
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### `App.razor`
```cs
< Router AppAssembly = " @typeof (Program).Assembly" PreferExactMatches = " @true " >
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< Found Context = "routeData" > // for component routing
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< RouteView RouteData = " @routeData " DefaultLayout = " @typeof (MainLayout)" />
< / Found >
< NotFound >
< LayoutView Layout = " @typeof (MainLayout)" >
< p > Sorry, there's nothing at this address.< / p >
< / LayoutView >
< / NotFound >
< / Router >
```
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### `MainLayout.razor` (Blazor Server/WASM)
```cs
@inherits LayoutComponentBase
< div class = "page" >
< div class = "sidebar" >
< NavMenu / > // NavMenu Component
< / div >
< div class = "main" >
< div class = "top-row px-4" >
< / div >
< div class = "content px-4" >
@Body
< / div >
< / div >
< / div >
```
### `_Host.cshtml` (Blazor Server)
```html
@page "/"
@namespace BlazorServerDemo.Pages
@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
@{
Layout = null;
}
<!DOCTYPE html>
< html lang = "en" >
< head >
< meta charset = "utf-8" / >
< meta name = "viewport" content = "width=device-width, initial-scale=1.0" / >
< title > BlazorServerDemo< / title >
< base href = "~/" / >
< link rel = "stylesheet" href = "css/bootstrap/bootstrap.min.css" / >
< link href = "css/site.css" rel = "stylesheet" / >
< link href = "BlazorServerDemo.styles.css" rel = "stylesheet" / >
< / head >
< body >
< component type = "typeof(App)" render-mode = "ServerPrerendered" / >
< div id = "blazor-error-ui" >
< environment include = "Staging,Production" >
An error has occurred. This application may no longer respond until reloaded.
< / environment >
< environment include = "Development" >
An unhandled exception has occurred. See browser dev tools for details.
< / environment >
< a href = "" class = "reload" > Reload< / a >
< a class = "dismiss" > 🗙< / a >
< / div >
< script src = "_framework/blazor.server.js" > < / script >
< / body >
< / html >
```
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## Components (`.razor`)
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[Blazor Components ](https://docs.microsoft.com/en-us/aspnet/core/blazor/components/ )
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```cs
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@page "/route/{RouteParameter?}" // make component accessible from a URL (optional)
@namespace < Namespace > // set the component namespace
@using < Namespace > // using statement
@inherits BaseType // inheritance
@attribute [Attribute] // apply an attribute
@inject Type objectName // dependency injection
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// html of the page here
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< Namespace.ComponentFolder.Component /> // access component w/o @using
< Component Property = "value" / > // insert component into page, passing attributes
< Component @onclick =" @CallbackMethod " >
@ChildContent // segment of UI content
< / Component >
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@code {
// component model (Properties, Methods, ...)
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[Parameter] // capture attribute
public Type Property { get; set; } = defaultValue;
[Parameter] // capture route parameters
public type RouteParameter { get; set;}
[Parameter] // segment of UI content
public RenderFragment ChildContent { get; set;}
private void CallbackMethod() { }
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}
```
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## Javascript/.NET Interop
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[Call Javascript from .NET ](https://docs.microsoft.com/en-us/aspnet/core/blazor/call-javascript-from-dotnet )
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[Call .NET from Javascript ](https://docs.microsoft.com/en-us/aspnet/core/blazor/call-dotnet-from-javascript )
