Rider EAP 20 fixes a number of bugs, improves .NET Core support, has better NuGet performance, supports Xamarin Android applications, comes with Node.js tooling from WebStorm (including SpyJS), can generate ResX files, executes T4 templates (needs Windows and Visual Studio SDK), adds support for scratch files, … Too much for one sentence, as you can see from the full list of fixes. We’ll highlight a few, read on! 

• Delete option is missing from solution explorer context menu in Xamarin Forms Android projects.
• Xamarin.Android: Can't select target framework 28 in Android Manifest settings.
• Could not load file or assembly 'Microsoft.VisualStudio.Web.PageInspector.Loader, Version=1.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.
• "There was an error running the selected code generator" when trying to create a new view.
• Android Berechtigungsliste ist leer-Android permission list is empty.
• Missing icons for .axml files in Visual Studio 2019.
• axml icons are not displayed.
• Visual Studio extensions may fail to install attempting to overwrite core NuGet files.
• C# switch statement on a constant expression may produce bad compiler errors. 

WinSCP.SessionRemoteException: Lost connection.

Timeout detected. (data connection)

Copying files to remote side failed.
Copying files to remote side failed.

#OS junk files
[Tt]humbs.db
*.DS_Store

#Visual Studio files
*.[Oo]bj
*.user
*.aps
*.pch
*.vspscc
*.vssscc
*_i.c
*_p.c
*.ncb
*.suo
*.tlb
*.tlh
*.bak
*.[Cc]ache
*.ilk
*.log
*.lib
*.sbr
*.sdf
*.opensdf
*.unsuccessfulbuild
ipch/
obj/
[Bb]in
[Dd]ebug*/
[Rr]elease*/
Ankh.NoLoad

#MonoDevelop
*.pidb
*.userprefs

#Tooling
_ReSharper*/
*.resharper
[Tt]est[Rr]esult*
*.sass-cache

#Project files
[Bb]uild/

#Subversion files
.svn

# Office Temp Files
~$*

#NuGet
packages/

#ncrunch
*ncrunch*
*crunch*.local.xml

# visual studio database projects
*.dbmdl

#Test files
*.testsettings

These are the customer-reported issues addressed in 15.9.4:

• Visual Studio 15.9 duplicate loads open files on solution reload.
• All users can now connect to on-premise TFS servers through Team Explorer.
• Visual Studio 15.8.3 no longer expands metadata in ItemDefinitionGroup for project-defined items during GUI builds (worked in Visual Studio 15.8.2).
• Visual Studio has multiple tabs for the same file.
• System.ArgumentException: The parameter is incorrect. (Exception from HRESULT: 0x80070057 (E_INVALIDARG)).
• LNK4099 PDB not found.
• Asset Catalog empty.
• /analyze fails for C++ code using /ZW.
• C++ compiler code optimization bug.
• Xamarin.iOS can't select image asset for Image View.
• iOS projects referencing a shared project containing image assets in an asset catalog fail to load on windows.
• Image not populating on iOS splashscreen in VS 15.8.6.
• Possible bad codegen on union/bitfield assignment in VS2017 15.8.
• Fix C# UWP Store 1201 Submission Issue.
• Fix C# UWP package creation error APPX1101: Payload contains two or more files with the same destination path 'System.Runtime.CompilerServices.Unsafe.dll'.
• Error MT2002: Failed to resolve 'System.Runtime.CompilerServices.AsyncValueTaskMethodBuilder' reference from 'System.Threading.Tasks.Extensions...'" when building a Xamarin.iOS project.
• Redirecting to a relative url doesn't work when using AndroidClientHandler.
• Debug information for typedefs of unnamed enums compiled with the C compiler is now restored.
• The spectre-mitigated x86 version of delayimp.lib is now built with /Qspectre mitigations enabled.
• Changes were made to how Asset Catalogs in Xamarin.iOS projects are loaded in order to reduce solution load time.
• We have updated Xamarin.Forms templates to use the latest version.
• We have fixed an issue with ASP.NET Core Web Applications being debugged through Kestrel that would show the error message "Unable to configure HTTPS endpoint. No server certificate was specified...".
• Enabling the AppInsights site extension in App Service from Visual Studio now happens through the use of specific Application Settings.

Security Advisory Notices

• An elevation of privilege vulnerability exists when the Diagnostics Hub Standard Collector Service improperly handles certain file operations. 

dotnet new sln

>dotnet sln add mymvc/mymvc.csproj
Project `mymvc\mymvc.csproj` added to the solution.
>dotnet sln add models/models.csproj
Project `models\models.csproj` added to the solution.

WinMerge is an Open Source differencing and merging tool for Windows. WinMerge can compare both folders and files, presenting differences in a visual text format that is easy to understand and handle. 

The tooltip that shows the expression type (Cmd/Ctrl-hover) in JavaScript and TypeScript files now has a syntax highlighting.