The specified version of microsoft.netcore.app or microsoft.aspnetcore.app was not found.

The error message “the specified version of microsoft.netcore.app or microsoft.aspnetcore.app was not found” typically occurs when the required versions of .NET Core or ASP.NET Core applications are not installed on the system or are not referenced correctly in the project.

To resolve this issue, you can follow these steps:

1. Check the required versions: Ensure that you have the correct versions of microsoft.netcore.app or microsoft.aspnetcore.app installed on your system. You can visit the official Microsoft website or use package managers like NuGet to install the required versions.
2. Update project references: If you have the correct versions installed but still encounter the error, check if the project references are correct. Open your project file (such as .csproj or .vbproj) and verify that the references to microsoft.netcore.app or microsoft.aspnetcore.app are properly defined. You may need to update the versions or re-add the references if they are missing.

Here is an example of how project references can be defined in a .csproj file:

    
      <ItemGroup>
        <PackageReference Include="Microsoft.NETCore.App" Version="3.1.0" />
      </ItemGroup>
    
  

In this example, the project requires version 3.1.0 of microsoft.netcore.app.

By ensuring the correct versions are installed and referenced properly, you should be able to resolve the “the specified version of microsoft.netcore.app or microsoft.aspnetcore.app was not found” error.