Hi @李畋岷 ,
First, to create asp.net core application in VS 2019, please check your Asp.net core version and the VS 2019 version, because the Asp.net core has the VS version requirement, like this:
More detail information, you could check the .Net SDK download page.
Then, to develop the application by team, you can work with the Git provider of your choice, such as GitHub or Azure DevOps.
Refer the following articles:
How Visual Studio makes version control easy with Git
Clone a Git repository in Visual Studio
Compare the Git experience to Team Explorer in Visual Studio 2019
Connect to projects in Team Explorer
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Best regards,
Dillion