ASP.NET Core 2.2.0 Preview 3 known issues

[Eilon]

Known issues in ASP.NET / Entity Framework Core 2.2 Preview 3

To see all issues closed in the 2.2.0 Preview 3 milestone, see the results of this query.

Official announcement blog post: https://blogs.msdn.microsoft.com/webdev/2018/10/17/asp-net-core-2-2-0-preview3-now-available/

Please see below for a list of known issues in the 2.2.0 Preview 3 release.

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Some external CSS styles are failing to load for new Razor and MVC projects:

When running a newly created MVC or Razor Pages project, some styles do not render.

This is caused by an integrity check failure for some of the referenced stylesheets. To fix the issue add a crossorigin="anonymous" attribute to the bootstrap.min.css referencing <link ...> tag in the _Layout.cshtml file, as follows:

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.3/css/bootstrap.min.css" 
	asp-fallback-href="~/lib/bootstrap/dist/css/bootstrap.min.css" 
	asp-fallback-test-class="sr-only" asp-fallback-test-property="position" asp-fallback-test-value="absolute" 
	crossorigin="anonymous" 
	integrity="sha256-eSi1q2PG6J7g7ib17yAaWMcrr5GrtohYChqibrV7PBE="/>

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URL generation for conventional routes with default values is invalid

In an MVC project using Endpoint Routing, URL generation using IUrlHelper can generate a URL incorrectly when the route template includes default values.

Example:

app.UseMvc(routes =>
{
    routes.MapRoute("default", "{controller=Home}/{action=Index}/{id?}");
});

Url.Action("Index", "Home", new { id = 17 });

This can result in the following URL being generated /?id=17 - this will work with most uses of MVC but the result of /Home/Index/17 is intended.

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NullReferenceException thrown when using IHttpClientFactory

Crashes can occur due to a bug in how cleanup timers are incorrectly started when using IHttpClientFactory. This can be worked around by setting HttpClientFactoryOptions.HandlerLifetime to an extremely long value or Timeout.InfiniteTimespan.

aspnet/HttpClientFactory#194

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For discussions, please go to dotnet/aspnetcore#3642