rynowak

Routing in the small

ASP.NET Core 3.0 adds new some infrastructure that makes programming in the small (few methods/classes) more convenient.

These scenarios feel more immediate when you can use local functions, and it really benefits from being able to place attributes on them. In particular, placing attributes on parameters is one of the only ways we can provide expressiveness about where the arguments should come from (injecting a DbContext from services in my example).

Using lambdas is an option as well, but for many of these cases the user wants to explicitly specify the types, so it's a small jump in complexity to a local function.

I'm not sure which of these we'd pick stylistically for our samples/blogs - but I'm sure some users will want to do this and it's come up during our internal discussions. I wanted to pass on the feedback about this feature, we have a concrete use case for it.

rynowak

LOL What?

Allows you to write methods that contain mixed HTML and C# in Razor Views (.cshtml) / Razor Components (.razor) files.

This is a primitive for composing Razor code that is very low overhead / low concept. Your code calls your code.

In Views (not components): Can be async, can use tag helpers. In Components (not views): Usage and semantics still need figuring out, but we want to build something like this.

Sample

rynowak

# Go paste this into http://viz-js.com/

digraph DFA {
0 -> 1 [label="/emojis"]
0 -> 4 [label="/events"]
0 -> 7 [label="/feeds"]
0 -> 10 [label="/gists"]
0 -> 80 [label="/issues"]
0 -> 83 [label="/markdown"]
0 -> 89 [label="/meta"]

rynowak

Summary

Routing has a URL generation that feature that tries to make it simple and terse to generate URLs to related endpoints. This involves allowing ambient route values to be used in URL generation to obviate the need to re-specify them. Route value invalidation is the set of rules that govern the cases where routing can and cannot use the ambient values.

Example (Conventional Routing)

public class BlogController : Controller
{
 // Assume we just matched the route "{controller=Home}/{action=Index}/{id?}

rynowak

Issues:

• Partials used from overridable views need to go into Views/Shared or Pages/Shared in the app. Partials used from the app's layout also need to go into Views/Shared or Pages/Shared in the app. Using other search paths may work well until you start overriding things.

• @namespace, @using and @addTagHelper are all problematic when it comes to copy-pasting code from a library into an app.

• build-time errors for razor show up in errors window in VS, but clicking on them doesn't work.

We don't have a gesture to remove/hide a precompiled Razor assembly. Identity will need to disable its precompiled Razor assets by default. Without this feature the precompiled Razor Pages show up when areas are enabled (fails to resolve services) - and do not show up when areas are disabled.

Not Razor Related

rynowak

Introduction to Razor Pages

Razor Pages is a new feature to ASP.NET Core MVC that makes coding page-focused scenarios easier and more productive.

Razor Pages is included in version 2.0.0 of ASP.NET Core. Tooling support for Razor Pages in Visual Studio ships in Visual Studio 2017 Update 3.

Getting Started

Razor Pages is on by default by MVC. If you are using a typical Startup.cs like the following, Razor Pages is already enabled.

rynowak

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Microsoft.VisualStudio.LanguageServices.Razor.New
{
    public abstract class TagHelperDescriptor

rynowak

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Routing;
using Microsoft.AspNetCore.Routing.Internal;
using Microsoft.AspNetCore.Routing.Template;
using Microsoft.AspNetCore.Routing.Tree;
using Microsoft.Extensions.Logging;

rynowak

Routing and MVC

ASP.NET MVC uses the Routing middleware to match the URLs of incoming requests and map them to actions. Routes are defined in startup code or using attributes and describe how URL paths should be matched to actions. MVC also uses the same set of routes to generate URLs to include as links in responses.

This document will explain the interactions between MVC and routing, and how typical MVC applications make sure of routing features. See the for details on how to write more advanced routes.

Setting up Routing Middleware

In your Configure method you may see code like:

rynowak

$sdk_dir = get-item "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.0"
$crossgen_exe = get-item "C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.0\crossgen.exe"
$pwd = get-item .

foreach ($file in gci . -r -include *.dll)
{
    $out =[io.path]::ChangeExtension($file.Name, ".ni.dll")
    write-host $crossgen_exe /Platform_Assemblies_Paths """$sdk_dir""" /App_Paths """$pwd"""/out $out $file
    & $crossgen_exe /Platform_Assemblies_Paths """$sdk_dir""" /App_Paths """$pwd"""/out $out $file