Here's the list of what's new in this preview:

• Razor Components
• SignalR client-to-server streaming
• Pipes on HttpContext
• Generic host in templates
• Endpoint routing updates 

Today, we’re announcing .NET Core 3.1 Preview 1. .NET Core 3.1 will be a small release focused on key improvements in Blazor and Windows desktop, the two big additions in .NET Core 3.0. It will be a long term support (LTS) release with an expected final ship date of December 2019. 

To get started with ASP.NET Core in .NET Core 3.0 Preview 9 install the .NET Core 3.0 Preview 9 SDK.

If you’re on Windows using Visual Studio, install the latest preview of Visual Studio 2019.

.NET Core 3.0 Preview 9 requires Visual Studio 2019 16.3 Preview 3 or later. 

Today, we are announcing .NET Core 3.0 Preview 3. We would like to update you on the .NET Core 3.0 schedule and introduce you to improvements in .NET Core SDK installers, Docker containers, Range, and Index. We also have updates on the Windows Desktop and Entity Framework projects. 

 http://en.هشام.com/post/build-customizable-language-switcher-tag-helper-with-bootstrap

 WebRequest wr = WebRequest.Create(uri);
using (WebResponse response = wr.GetResponse()) { }

 The remote name could not be resolved: 'en.هشام.com'

<configuration>
    <uri>
        <idn enabled="All" />
        <iriParsing enabled="true" />
    </uri>
</configuration>

 var unicode = @"en.هشام.com";
 
var mapping = new IdnMapping(); // IDN  = Internationalizing Domain Names
var ascii = mapping.GetAscii(unicode);
Console.WriteLine(ascii);
 
string convertedBackToUnicode = mapping.GetUnicode(ascii);
Console.WriteLine(convertedBackToUnicode);

Continuing with our release cadence, we’re excited to announce the release of SQL Server 2022 Release Candidate 1. Since the first public preview in May 2022, anyone can download SQL Server 2022 RC1 to try the new features in this release. 

• We added support to change installation locations.
• You can Save All your pending changes before you start your update.
• The update dialog provides you even more details about your update during installation.
• C# 7.3 is included in Visual Studio version 15.7.
• We improved solution load time for C# and VB projects.
• We made numerous updates to F# and its tools, with a focus on performance.
• We reduced the time to enable IntelliSense for large .NET Core projects by 25%.
• We made Quick Info improvements and new .NET refactorings like convert for-to-foreach and make private fields readonly.
• We added the ability to publish ASP.NET Core applications to App Service Linux without containers.
• Live Unit Testing works with embedded pdbs and supports projects that use reference assemblies.
• The Test Explorer has more responsive icons during test runs.
• C++ developers can use CodeLens for unit testing.
• We added new rules enforcing items from the C++ Core Guidelines.
• Debugging large solutions with /Debug:fastlink PDBs is more robust.
• CMake integration supports CMake 3.11 and static analysis.
• Python projects support type hints in IntelliSense, and a Run MyPy command has been added to look for typing errors in your code.
• Conda environments are supported in Python projects.
• We added a next version of our Python debugger based on the popular open source pydevd debugger.
• TypeScript 2.8 is included in Visual Studio version 15.7.
• We improved Kestrel HTTPs support during debugging.
• We added support for JavaScript debugging with Microsoft Edge.
• The Debugger supports VSTS and GitHub Authentication for Source Link.
• IntelliTrace’s step-back debugging feature is supported for debugging .NET Core projects.
• We added IntelliTrace support for taking snapshots on exceptions.
• We removed the blocking modal dialog from branch checkouts in Git when a solution or project reload is not required.
• There is an option to choose between OpenSSL and SChannel in Git.
• You can create and associate Azure Key Vaults from within the Visual Studio IDE.
• Visual Studio Tools for Xamarin can automatically install missing Android API levels required by Xamarin.Android projects.
• The Xamarin.Forms XAML editor provides IntelliSense and quick fixes for conditional XAML.
• We added support for Azure, UWP, and additional project types in Visual Studio Build Tools.
• You can create build servers without installing all of Visual Studio.
• The Windows 10 April 2018 Update SDK - Build 17134 is the default required SDK for the Universal Windows Platform development workload.
• We added support for Visual State Management for all UWP apps and more.
• We enabled automatic updates for sideloaded APPX packages.
• You have new tools for migrating to NuGet PackageReference.
• We added support for NuGet package signatures.
• We added Service Fabric Tooling for the 6.2 Service Fabric release.
• We updated Entity Framework Tools to work with the EF 6.2 runtime and to improve reverse engineering of existing databases.