Issue when creating a new ASP.NET Core 6.0 Web API

Question

I tried to create a new Web API in ASP.NET Core 6.0 as shown https://learn.microsoft.com/en-us/aspnet/core/tutorials/first-web-api?view=aspnetcore-6.0&tabs=visual-studio-code#create-a-web-project.

But it is created with errors.

This is the WeatherForecastController of my new project:

using Microsoft.AspNetCore.Mvc;

// see here This is ends with ";". And showing this error "{ expected [TodoApi]"
namespace TodoApi.Controllers; 

[ApiController]
[Route("[controller]")]
public class WeatherForecastController : ControllerBase
{
    // some code
}

And the WeatherForecast class looks like this

// see here This is ends with ";". And showing this error "{ expected [TodoApi]"
namespace TodoApi;   

public class WeatherForecast
{
    // some code
}

And all namespaces are missing.

program.cs file looks like this; it does not have any namespace when created:

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllers();

// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

//.......

And TodoApi.GlobalUsings.g.cs file also has errors

// <auto-generated/>
global using global::Microsoft.AspNetCore.Builder;
global using global::Microsoft.AspNetCore.Hosting;
global using global::Microsoft.AspNetCore.Http;
global using global::Microsoft.AspNetCore.Routing;
global using global::Microsoft.Extensions.Configuration;
global using global::Microsoft.Extensions.DependencyInjection;
global using global::Microsoft.Extensions.Hosting;
global using global::Microsoft.Extensions.Logging;
global using global::System;
global using global::System.Collections.Generic;
global using global::System.IO;
global using global::System.Linq;
global using global::System.Net.Http;
global using global::System.Net.Http.Json;
global using global::System.Threading;
global using global::System.Threading.Tasks;

The output of dotnet --info is

.NET SDK (reflecting any global.json):
 Version:   6.0.100
 Commit:    9e8b04bbff

Runtime Environment:
 OS Name:     ubuntu
 OS Version:  20.04
 OS Platform: Linux
 RID:         ubuntu.20.04-x64
 Base Path:   /snap/dotnet-sdk/147/sdk/6.0.100/

Host (useful for support):
  Version: 6.0.0
  Commit:  4822e3c3aa

.NET SDKs installed:
  6.0.100 [/snap/dotnet-sdk/147/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 6.0.0 [/snap/dotnet-sdk/147/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 6.0.0 [/snap/dotnet-sdk/147/shared/Microsoft.NETCore.App]

To install additional .NET runtimes or SDKs:
  https://aka.ms/dotnet-download

But if I create an ASP.NET Core 3.1 project, it does not show these errors (I installed ASP.NET Core 3.1 to create ASP.NET Core 3.1 Web API).

I don't know why these errors occurs when creating a new ASP.NET Core 6.0 Web API project.

Does anyone know ?

Edit : I am using visual studio code. and TodoApi.csproj

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="6.0.0" />
    <PackageReference Include="Swashbuckle.AspNetCore" Version="6.2.3" />
  </ItemGroup>

</Project>

Answer 1

There are several new features of C# at play here.

First of all in Program.cs the Program class is "missing" because of a new feature called "Top level programs".

https://devblogs.microsoft.com/dotnet/c-9-0-on-the-record/#top-level-programs

The missing namespaces are because of "Global and implicit usings" which give you some standard namespaces included globally.

https://devblogs.microsoft.com/dotnet/announcing-net-6/#global-using-directives

As for the namespace with a semicolon after that is a "File scoped namespace" which is the same as wrapping the whole file in a namespace but without needing to indent everything.

https://devblogs.microsoft.com/dotnet/announcing-net-6/#file-scoped-namespaces

If you are using Visual Studio 2019 you will need to update to Visual Studio 2022 to use all these features. VSCode should automaticly update the C# extension to the latest version but if it hasn't (or you have disabled automatic updates) you might need to update it manually.

https://marketplace.visualstudio.com/items?itemName=ms-dotnettools.csharp