I want to test the new Blazor server-side framework (aka Razor Components).
I installed Visual Studio 2019 RC, and then the .Net Core 3.0 preview 2, following this official tutorial.
After the install, I only see the ASP.NET Core 2.0 and the 2.1 on the "Create a new ASP.NET Core Web Application" page. The 3.0 is not showing up.
I started to mess around, trying to install other packages from this page, uninstalled and reinstalled Visual Studio 2019, updated to the .NET Core Preview 3, installed several times the x64 and x86 packages in different orders, copy/paste the .Net Core binaries to random folders and so on. Nothing works. The ASP.NET Core 3.0 does not show up.
Here is what my VS looks like when creating a project (the yellow message appeared latter after some messing around with the packages, so it is not the real problem):
Here is the output of the dotnet --list-sdks command:
EDIT
For some reason, I installed the Blazor VSIX package (the WebAssembly - not exactly what I want, but I installed it anyways) and now the ASP.NET Core 3.0 simply shows up. However, just for the blazor templates:
I don't understand. Is there anything obvious I'm missing?
There is an option in Tools -> Options that enables preview versions of the .NET Core SDK. In the VS Preview shipping channel, it is on (by default, and not settable). In the VS Release channel, it defaults to off and you can opt-in.
(Note: it's disabled in the screenshot because I have a Preview build installed.)
The reason for this is to allow you to customize whether a project using a released version of .NET Core (such as 2.1, the current LTS) will use tooling from the newer not-yet-release-quality SDK.
Prior to 16.1, this option was located on the Tools -> Options -> Projects and Solutions -> .NET Core page.
I have the same issue here after moving from Visual Studio 2019 Preview to Visual Studio 2019 RC.
This page seems to suggest that you need Preview to use .net Core 3.0 which is annoying.
https://dotnet.microsoft.com/download/dotnet-core/3.0
I looked up the difference between RC and Preview, and they pull builds from different channels (stable and preview).
The next thing I’m going to try is to go back to Preview to see if .Net Core 3.0 becomes visible again.
Tried to get .NET Core 3 (preview 8 in my case) to work in the release version of Visual Studio 2019 but ASP.NET Core 3.0 refused to show up in the "Create new ASP.NET Core web application" dialog.
What eventually worked was to install the Preview version of Visual Studio 2019.
I could have saved a few hours and a lot of hair if I had taken the warning text ".NET Core 3.0 should be used with the latest previews of Visual Studio." (https://dotnet.microsoft.com/download/dotnet-core/3.0) more literally...
In my case is because I did not installed Visual Studio 2019 with that feature. So just create a new project and type .net core. Then click on Install more tools and features:
Then add the following feature:
Note! (don't use it on your developer machine)
0- make sure you installed .net core 3 sdk. dotnet --list-sdks
1- make sure Tools -> Options that enables preview versions of the .NET Core SDK enabled.
2- uninstall all x86 version of .net core sdk from your machine.
3- restart visual studio and try to create a new project.
After working around with suggested solutions that didn't work for me I uninstalled ".net core SDK 3.0.100-preview8-013656" and I installed ".net core SDK 3.0.100-preview7-012821" instead: .net core SDK 3.0.100-preview7-012821
With this version I was able to target .net core 3.0 (and respective templates) in Visual Studio 2019 Community Edition:
来源：https://stackoverflow.com/questions/55032756/asp-net-core-3-0-not-showing-on-visual-studio-2019