Last update: Septemer 6, 2025

Create a Blazor WebAssembly ASP.NET Core hosted solution for .NET 9

You can host a Blazor WebAssembly App as a static website, e.g. in Azure Storage, but because we use an ASP.NET Core Api, I prefer to use an Api project for hosting. But I do not want a Blazor Server or Blazor Hybrid app. I prefer the WebAssembly app: the code in the browser is running completely independent and only uses Api calls to the server.

Previously, Visual Studio had a template to create an ASP.NET Core hosted Blazor WebAssembly solution. Unfortunately, this project template is not available anymore, except for an old teplate which sticks to .NET 7 (Blazor WebAssembly App Empty)

This way you can easily create a Blazor WebAssembly ASP.NET Core hosted solution for .NET 9:

See also the example app in github.

1. Use the Visual Studio template Blazor WebAssembly Standalone App, select .NET 9 and name the project (here: BlazorExample.Client).
2. Add a new project to the solution using the template ASP.NET Core Web API, select .NET 9 and Use controllers and name the project (here: BlazorExample.Server)
3. Add Nuget package to the server project: Microsoft.AspNetCore.Components.WebAssembly.Server

4. Add a reference in the server project to the client project

5. In the server project edit Program.cs and add the lines between the lines:

   public static void Main(string[] args)
   {
    var builder = WebApplication.CreateBuilder(args);
    builder.Services.AddControllers();
    // TODO: Add your own services.
    var app = builder.Build();
    // ADD ------------------------------------
    if (app.Environment.IsDevelopment())
        app.UseWebAssemblyDebugging();
    // ------------------------------------
    app.UseHttpsRedirection();
    // ADD ------------------------------------
    app.UseBlazorFrameworkFiles();
    app.UseStaticFiles();
    app.UseRouting();
    // ------------------------------------
    app.UseAuthorization();
    app.MapControllers();
    // ADD ------------------------------------
    app.MapFallbackToFile("index.html");
    // ------------------------------------
    app.Run();
   }
   

6. In the server project change Properties/launchSettings.json (you can use other port numbers if you like):

{
  "profiles": {
	"http": {
	  "commandName": "Project",
	  "launchBrowser": true,
	  "environmentVariables": {
		"ASPNETCORE_ENVIRONMENT": "Development"
	  },
	  "dotnetRunMessages": true,
	  "inspectUri": "{wsProtocol}://{url.hostname}:{url.port}/_framework/debug/ws-proxy?browser={browserInspectUri}",
	  "applicationUrl": "http://localhost:5225"
	},
	"https": {
	  "commandName": "Project",
	  "launchBrowser": true,
	  "environmentVariables": {
		"ASPNETCORE_ENVIRONMENT": "Development"
	  },
	  "dotnetRunMessages": true,
	  "inspectUri": "{wsProtocol}://{url.hostname}:{url.port}/_framework/debug/ws-proxy?browser={browserInspectUri}",
	  "applicationUrl": "https://localhost:7283;http://localhost:5225"
	},
	"IIS Express": {
	  "commandName": "IISExpress",
	  "launchBrowser": true,
	  "environmentVariables": {
		"ASPNETCORE_ENVIRONMENT": "Development"
	  },
	  "inspectUri": "{wsProtocol}://{url.hostname}:{url.port}/_framework/debug/ws-proxy?browser={browserInspectUri}"
	}
  },
  "iisExpress": {
	"applicationUrl": "http://localhost:26936",
	"sslPort": 44351
  },
  "iisSettings": {
	"windowsAuthentication": false,
	"anonymousAuthentication": true,
	"iisExpress": {
	  "applicationUrl": "http://localhost:65397/",
	  "sslPort": 44373
	}
  }
}