Tutorial: Create an ASP.NET Core app with React in Visual Studio

Artikkeli
11/06/2024

In this article, you learn how to build an ASP.NET Core project to act as an API backend and a React project to act as the UI.

Currently, Visual Studio includes ASP.NET Core Single Page Application (SPA) templates that support Angular and React. The templates provide a built-in Client App folder in your ASP.NET Core projects that contains the base files and folders of each framework.

You can use the method described in this article to create ASP.NET Core Single Page Applications that:

Put the client app in a separate project, outside from the ASP.NET Core project
Create the client project based on the framework CLI installed on your computer

Note

This article describes the project creation process using the updated template in Visual Studio 2022 version 17.11, which uses the Vite CLI.

Prerequisites

Visual Studio 2022 version 17.11 or later with the ASP.NET and web development workload installed. Go to the Visual Studio downloads page to install it for free. If you need to install the workload and already have Visual Studio, go to Tools > Get Tools and Features..., which opens the Visual Studio Installer. Choose the ASP.NET and web development workload, then choose Modify.
npm (https://www.npmjs.com/), which is included with Node.js

Create the frontend app

In the Start window, select Create a new project.
Search for React in the search bar at the top and then select React and ASP.NET Core. This template is a JavaScript template.
Name the project ReactWithASP and then select Next.

In the Additional Information dialog, make sure that Configure for HTTPS is enabled. In most scenarios, leave the other settings at the default values.
Select Create.

Solution Explorer shows the following project information:

Compared to the standalone React template, you see some new and modified files for integration with ASP.NET Core:
- vite.config.js
- App.js (modified)
- App.test.js (modified)
Select an installed browser from the Debug toolbar, such as Chrome or Microsoft Edge.

If the browser you want is not yet installed, install the browser first, and then select it.

Set the project properties

In Solution Explorer, right-click the ReactWithASP.Server project and choose Properties.
In the Properties page, open the Debug tab and select Open debug launch profiles UI option. Uncheck the Launch Browser option for the https profile or the profile named after the ASP.NET Core project, if present.

This value prevents opening the web page with the source weather data.

Note

In Visual Studio, launch.json stores the startup settings associated with the Start button in the Debug toolbar. Currently, launch.json must be located under the .vscode folder.
Right-click the solution in Solution Explorer and select Properties. Verify that the Startup project settings are set to Multiple projects, and that the Action for both projects is set to Start.

Start the project

Press F5 or select the Start button at the top of the window to start the app. Two command prompts appear:

The ASP.NET Core API project running
The Vite CLI showing a message such as VITE v4.4.9 ready in 780 ms

Note

Check console output for messages. For example there might be a message to update Node.js.

The React app appears and is populated via the API. If you don't see the app, see Troubleshooting.

Publish the project

In Solution Explorer, right-click the ReactWithASP.Server project and select Add > Project Reference.

Make sure the reactwithasp.client project is selected.
Choose OK.
Right-click the ASP.NET Core project again and select Edit Project File.

This opens the .csproj file for the project.
In the .csproj file, make sure the project reference includes a <ReferenceOutputAssembly> element with the value set to false.

This reference should look like the following.
```
 <ProjectReference Include="..\reactwithasp.client\reactwithasp.client.esproj">
   <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
 </ProjectReference>
```
Right-click the ASP.NET Core project and choose Reload Project if that option is available.

In Program.cs, make sure the following code is present.

app.UseDefaultFiles();
app.UseStaticFiles();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
   app.UseSwagger();
   app.UseSwaggerUI();
}

To publish, right click the ASP.NET Core project, choose Publish, and select options to match your desired publish scenario, such as Azure, publish to a folder, etc.

The publish process takes more time than it does for just an ASP.NET Core project, since the npm run build command gets invoked when publishing. The BuildCommand runs npm run build by default.

If you publish to a folder, see ASP.NET Core directory structure for more information on the files added to the publish folder.

Troubleshooting

Proxy error

You may see the following error:

[HPM] Error occurred while trying to proxy request /weatherforecast from localhost:4200 to https://localhost:7183 (ECONNREFUSED) (https://nodejs.org/api/errors.html#errors_common_system_errors)

If you see this issue, most likely the frontend started before the backend.

Once you see the backend command prompt up and running, just refresh the React app in the browser.
Also, verify that the backend is configured to start before the front end. To verify, select the solution in Solution Explorer, choose Properties from the Project menu. Next, select Configure Startup Projects and make sure that the backend ASP.NET Core project is first in the list. If it's not first, select the project and use the Up arrow button to make it the first project in the launch list.

Verify ports

If the weather data doesn't load correctly, you may also need to verify that your ports are correct.

Make sure that the port numbers match. Go to the launchSettings.json file in the ASP.NET Core ReactWithASP.Server project (in the Properties folder). Get the port number from the applicationUrl property.

If there are multiple applicationUrl properties, look for one using an https endpoint. It looks similar to https://localhost:7183.
Open the vite.config.js file for the React project. Update the target property to match the applicationUrl property in launchSettings.json. The updated value looks similar to the following:
```
target: 'https://localhost:7183/',
```

Privacy error

You may see the following certificate error:

Your connection isn't private

Try deleting the React certificates from %appdata%\local\asp.net\https or %appdata%\roaming\asp.net\https, and then retry.

Docker

If you create the project with Docker support enabled, take the following steps:

After the app loads, get the Docker HTTPS port using the Containers window in Visual Studio. Check the Environment or Ports tab.
Open the vite.config.js file for the React project. Update the target variable to match the HTTPS port in the Containers window. For example, in the following code:
```
const target = env.ASPNETCORE_HTTPS_PORT ? `https://localhost:${env.ASPNETCORE_HTTPS_PORT}` :
   env.ASPNETCORE_URLS ? env.ASPNETCORE_URLS.split(';')[0] : 'https://localhost:7143';
```
change https://localhost:7143 to the matching HTTPS port (in this example, https://localhost:44307).
Restart the app.

Next steps

For more information about SPA applications in ASP.NET Core, see the React section under Developing Single Page Apps. The linked article provides additional context for project files such as aspnetcore-https.js, although details of the implementation are different based on the template differences. For example, instead of a ClientApp folder, the React files are contained in a separate project.

For MSBuild information specific to the client project, see MSBuild properties for JSPS.

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