Add default global usings to Microsoft.NET.Sdk.Web

[halter73]

This is one of the bullet points from #30580. A long list of mostly the same using statements at the top of every ASP.NET Core is intimidating and ultimately unhelpful noise for the most point.

We should consider a set of name spaces that will be imported by default into all cs file in net6.0 projects targeting Microsoft.NET.Sdk.Web.

Here's a strawman proposal for the possible default namespaces to use:

[Edit: updated list as of 6/23]

global using global::System;
global using global::System.Collections.Generic;
global using global::System.Linq;
global using global::System.Net.Http;
global using global::System.Net.Http.Json;
global using global::System.Threading.Tasks;
global using global::Microsoft.AspNetCore.Builder;
global using global::Microsoft.AspNetCore.Hosting;
global using global::Microsoft.AspNetCore.Http;
global using global::Microsoft.AspNetCore.Mvc;
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; 

It's kinda crazy seeing .cs files without usings but I like it a lot.

We of course do need to be careful not to overdo this and introduce a bunch of conflicts or make intellisense too confusing. It's possible the strawman proposal is already a bit much, but I need to play with it more to get a good feeling for how convenient and/or annoying it is.

[benaadams]

global using System.Linq; 🙄

Also global using Microsoft.EntityFrameworkCore; could that be added to subpackages in some way instead? So its included if you add a provider to your project rather than by default if you are going another way (which could even be EF6 since that now runs on .NET6.0 and I assume most of the types will conflict and lead to much confusion)

[davidfowl]

Those shouldn't be in the ASP.NET one.

[davidfowl]

cc @DamianEdwards

[pranavkm]

Do these play well if a file already includes these usings?

[davidfowl]

Not yet (https://github.com/davidfowl/CommunityStandUpMinimalAPI/blob/386a0c1fef756e55a999429b8f8cba400ff3f4ca/Sample/Sample.csproj#L6).

I think it's interesting to discuss whether we want this in each project on on by default. Assuming we can stop the warning, I think we'd want a subset of namespaces in there by default.

[DamianEdwards]

Are we attempting to optimize for the top-level statements file or all files in the project? Today I feel the most friction is the amount of namespaces needed just to bootstrap a basic app in its Program/Startup classes and of course over time more instances of those will become merged into the top-level statements file using the minimal hosting API.

We also need to consider how this impacts existing apps that are simply used with the new SDK or just updated to target net6.0 without necessarily changing to use top-level statements or the minimal hosting API.

[halter73]

I would like to optimize for all files in a common ASP.NET Core project. I don't think there's a way to limit it to certain files.

[BrennanConroy]

Triage: We should consider having an msbuild property you can put in your csproj to disable the default usings. Or opt-in.