dev-notes/.NET/ASP.NET/Blazor.md
2021-05-01 11:56:14 +02:00

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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.
![Blazor Server Architecture](https://docs.microsoft.com/en-us/aspnet/core/blazor/index/_static/blazor-server.png)
![Blazor WASM Architecture](https://docs.microsoft.com/en-us/aspnet/core/blazor/index/_static/blazor-webassembly.png)
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
| |- _Host.cshtml --> fallback page
| |- 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
```
### `App.razor`
```cs
<Router AppAssembly="@typeof(Program).Assembly" PreferExactMatches="@true">
<Found Context="routeData"> // for component routing
<RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
</Found>
<NotFound>
<LayoutView Layout="@typeof(MainLayout)">
<p>Sorry, there's nothing at this address.</p>
</LayoutView>
</NotFound>
</Router>
```
### `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>
```
## Components (`.razor`)
[Blazor Components](https://docs.microsoft.com/en-us/aspnet/core/blazor/components/)
```cs
@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
// html of the page here
<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>
@code {
// component model (Properties, Methods, ...)
[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() { }
}
```
## Javascript/.NET Interop
[Call Javascript from .NET](https://docs.microsoft.com/en-us/aspnet/core/blazor/call-javascript-from-dotnet)
[Call .NET from Javascript](https://docs.microsoft.com/en-us/aspnet/core/blazor/call-dotnet-from-javascript)