Since IMiddleware exists, the "Write custom ASP.NET Core middleware" page should switch to using it.

### Description

[This page](https://learn.microsoft.com/en-us/aspnet/core/fundamentals/middleware/write?view=aspnetcore-9.0) describes methods of creation custom middlewares using the old, non-interfaced way, where you should either memorize or constantly check up with the docs of whether you've managed to guess the correct signature of both the `InvokeAsync` method AND the `RequestDelegate` parameter of the constructor.

The [`IMiddleware`](https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.http.imiddleware) was there since .NET Core 2.0 and I believe the need to nudge the developers to start using it is long overdue.

### Page URL

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/middleware/write?view=aspnetcore-9.0

### Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/fundamentals/middleware/write.md

### Document ID

cd22a135-4446-79f5-89db-b741bd44a720

### Article author

@Rick-Anderson

### Metadata

* ID: 13e2d968-17a6-1a50-53cd-1d6b9ad0276d
* PlatformId: f3890656-a128-4c55-0ed2-0882f2d05c6f
* Service: **aspnet-core**
* Sub-service: **fundamentals**

[Related Issues](https://github.com/dotnet/AspNetCore.Docs/issues?q=is%3Aissue+is%3Aopen+cd22a135-4446-79f5-89db-b741bd44a720)