In some projects I need to add NuGet package Microsoft.Data.SqlClient to the project before I can do

using Microsoft.Data.SqlClient

In other projects, I can do that without explicitly adding the NuGet package.
The examples below are both .NET 6.0 projects (same for .NET 5).

Referenced directly:

Not referenced directly:

I am wondering how this works.
Is the package referenced indirectly somehow?

>Solution :

AspNetCore.HealthChecks.SqlServer depends on Microsoft.Data.SqlClient:

• .NETStandard 2.0
  • Microsoft.Data.SqlClient (>= 2.1.2)
  • Microsoft.Extensions.Diagnostics.HealthChecks (>= 5.0.1)
• net5.0
  • Microsoft.Data.SqlClient (>= 2.1.2)
  • Microsoft.Extensions.Diagnostics.HealthChecks (>= 5.0.1)

so as transitive dependency Microsoft.Data.SqlClient becomes available for you also.