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Cristian Vasta

Cristian Vasta

4 years ago

ASP.NET Core Angular Project Template

The updated Angular project template provides a convenient starting point for ASP.NET Core apps using Angular and the Angular CLI to implement a rich, client-side user interface (UI).

The template is equivalent to creating an ASP.NET Core project to act as an API backend and an Angular CLI project to act as a UI. The template offers the convenience of hosting both project types in a single app project. Consequently, the app project can be built and published as a single unit.

Create a new app

If you have ASP.NET Core 2.1 installed, there’s no need to install the Angular project template.

Create a new project from a command prompt using the command dotnet new angular in an empty directory. For example, the following commands create the app in a my-new-app directory and switch to that directory:

dotnet new angular -o my-new-app
cd my-new-app

Run the app from either Visual Studio or the .NET Core CLI:

Visual Studio

Open the generated .csproj file, and run the app as normal from there.

The build process restores npm dependencies on the first run, which can take several minutes. Subsequent builds are much faster.

.NET Core CLI

Ensure you have an environment variable called ASPNETCORE_Environment with a value of Development. On Windows (in non-PowerShell prompts), run SET ASPNETCORE_Environment=Development. On Linux or macOS, run export ASPNETCORE_Environment=Development.

Run dotnet build to verify the app builds correctly. On the first run, the build process restores npm dependencies, which can take several minutes. Subsequent builds are much faster.

Run dotnet run to start the app. A message similar to the following is logged:

Now listening on: http://localhost:<port>

Navigate to this URL in a browser.

The app starts up an instance of the Angular CLI server in the background. A message similar to the following is logged: _NG Live Development Server is listening on localhost:<otherport>, open your browser on http://localhost:<otherport>/_. Ignore this message—it’s not the URL for the combined ASP.NET Core and Angular CLI app.

The project template creates an ASP.NET Core app and an Angular app. The ASP.NET Core app is intended to be used for data access, authorization, and other server-side concerns. The Angular app, residing in the ClientApp subdirectory, is intended to be used for all UI concerns.

Add pages, images, styles, modules, etc.

The ClientApp directory contains a standard Angular CLI app. See the official Angular documentation for more information.

There are slight differences between the Angular app created by this template and the one created by Angular CLI itself (via ng new); however, the app’s capabilities are unchanged. The app created by the template contains a Bootstrap-based layout and a basic routing example.

Run ng commands

In a command prompt, switch to the ClientApp subdirectory:

cd ClientApp

If you have the ng tool installed globally, you can run any of its commands. For example, you can run ng lint, ng test, or any of the other Angular CLI commands. There’s no need to run ng serve though, because your ASP.NET Core app deals with serving both server-side and client-side parts of your app. Internally, it uses ng serve in development.

If you don’t have the ng tool installed, run npm run ng instead. For example, you can run npm run ng lint or npm run ng test.

Install npm packages

To install third-party npm packages, use a command prompt in the ClientApp subdirectory. For example:

cd ClientApp
npm install --save <package_name>

Publish and deploy

In development, the app runs in a mode optimized for developer convenience. For example, JavaScript bundles include source maps (so that when debugging, you can see your original TypeScript code). The app watches for TypeScript, HTML, and CSS file changes on disk and automatically recompiles and reloads when it sees those files change.

In production, serve a version of your app that’s optimized for performance. This is configured to happen automatically. When you publish, the build configuration emits a minified, ahead-of-time (AoT) compiled build of your client-side code. Unlike the development build, the production build doesn’t require Node.js to be installed on the server (unless you have enabled server-side rendering (SSR)).

You can use standard ASP.NET Core hosting and deployment methods.

Run “ng serve” independently

The project is configured to start its own instance of the Angular CLI server in the background when the ASP.NET Core app starts in development mode. This is convenient because you don’t have to run a separate server manually.

There’s a drawback to this default setup. Each time you modify your C# code and your ASP.NET Core app needs to restart, the Angular CLI server restarts. Around 10 seconds is required to start back up. If you’re making frequent C# code edits and don’t want to wait for Angular CLI to restart, run the Angular CLI server externally, independently of the ASP.NET Core process. To do so:

  1. In a command prompt, switch to the ClientApp subdirectory, and launch the Angular CLI development server:

    cd ClientApp
npm start


Important

Use `npm start` to launch the Angular CLI development server, not `ng serve`, so that the configuration in _package.json_ is respected. To pass additional parameters to the Angular CLI server, add them to the relevant `scripts` line in your _package.json_ file.

  1. Modify your ASP.NET Core app to use the external Angular CLI instance instead of launching one of its own. In your Startup class, replace the spa.UseAngularCliServer invocation with the following:

    spa.UseProxyToSpaDevelopmentServer("http://localhost:4200");

When you start your ASP.NET Core app, it won’t launch an Angular CLI server. The instance you started manually is used instead. This enables it to start and restart faster. It’s no longer waiting for Angular CLI to rebuild your client app each time.

Pass data from .NET code into TypeScript code

During SSR, you might want to pass per-request data from your ASP.NET Core app into your Angular app. For example, you could pass cookie information or something read from a database. To do this, edit your Startup class. In the callback for UseSpaPrerendering, set a value for options.SupplyData such as the following:

options.SupplyData = (context, data) =>
{
    // Creates a new value called isHttpsRequest that's passed to TypeScript code
    data["isHttpsRequest"] = context.Request.IsHttps;
};

The SupplyData callback lets you pass arbitrary, per-request, JSON-serializable data (for example, strings, booleans, or numbers). Your main.server.ts code receives this as params.data. For example, the preceding code sample passes a boolean value as params.data.isHttpsRequest into the createServerRenderer callback. You can pass this to other parts of your app in any way supported by Angular. For example, see how main.server.ts passes the BASE_URL value to any component whose constructor is declared to receive it.

Drawbacks of SSR

Not all apps benefit from SSR. The primary benefit is perceived performance. Visitors reaching your app over a slow network connection or on slow mobile devices see the initial UI quickly, even if it takes a while to fetch or parse the JavaScript bundles. However, many SPAs are mainly used over fast, internal company networks on fast computers where the app appears almost instantly.

At the same time, there are significant drawbacks to enabling SSR. It adds complexity to your development process. Your code must run in two different environments: client-side and server-side (in a Node.js environment invoked from ASP.NET Core). Here are some things to bear in mind:

  • SSR requires a Node.js installation on your production servers. This is automatically the case for some deployment scenarios, such as Azure App Services, but not for others, such as Azure Service Fabric.

  • Enabling the BuildServerSideRenderer build flag causes your node_modules directory to publish. This folder contains 20,000+ files, which increases deployment time.

  • To run your code in a Node.js environment, it can’t rely on the existence of browser-specific JavaScript APIs such as window or localStorage. If your code (or some third-party library you reference) tries to use these APIs, you’ll get an error during SSR. For example, don’t use jQuery because it references browser-specific APIs in many places. To prevent errors, you must either avoid SSR or avoid browser-specific APIs or libraries. You can wrap any calls to such APIs in checks to ensure they aren’t invoked during SSR. For example, use a check such as the following in JavaScript or TypeScript code:

    if (typeof window !== 'undefined') {
    // Call browser-specific APIs here
}

#angular #aspdotnet

ASP.NET Core Angular Project Template
41.45 GEEK