How do I use the enhanced metadata format in C#?

[Tored]

Hello, I would like to automate the DataSet generation (using C#). In this context, I have encountered problems when I create the DataSet in Power BI Service (For more information: Data source information is not found in Power BI service ). For this reason, I am now trying to generate the DataSet within a Power BI file in an open Power BI Desktop instance. In doing so, I am running into an issue with the enhanced metadata format, which is what this thread is about.

My situation:

With my C# code, I connect to a PBIX file that is open in Power BI Desktop.
Then I add a new data source and a new table to the DataSet from the PBIX file.
After running the code, the table also appears in Power BI Desktop and I can use it.

My problem:
The message pops up (translated from German to English):
"No upgrade to use the enhanced metadata format has been performed for this report. The upgrade is required to make modeling changes."

There is also a button "Perform upgrade for report" and when I press it, my table disappears.

My questions:
How can I run such an upgrade (for using the enhanced metadata format) with C# code without my table disappearing afterwards or how do I use the enhanced metadata format in C#?

My requirements:
- PPU (Premium Per User) Trial License
- On Premise SQL Server
- Microsoft.AnalysisServices Package

My code:

// Get connection string to PowerBI-File
var connections = PowerBIDesktopUtilities.GetActiveDatasetConnections();
var connectionString = connections[1].ConnectString;

using (Microsoft.AnalysisServices.Tabular.Server server = new Microsoft.AnalysisServices.Tabular.Server())
{
   server.Connect(connectionString);
   var database = server.Databases[0];

   // Adding local SQL Server as data source
   string dataSource = "LocalSQLServer";
   bool expression = database.Model.DataSources.Contains(dataSource);
   if (!expression)
   {
      database.Model.DataSources.Add(new ProviderDataSource()
      {
         //[...]
      });
   }

   // Adding Table
   database.Model.Tables.Add(new Table()
   {
      Name = database.Model.Tables.GetNewName("Individual Customers"),
      Description = "Individual customers (names and email addresses) that purchase Adventure Works Cycles products online.",
      Partitions = {
         //[...]
      },
      Columns =
      { 
         //[...]
      }
   });

   database.Model.RequestRefresh(Microsoft.AnalysisServices.Tabular.RefreshType.Full);
   database.Update(UpdateOptions.ExpandFull);
}

Thanks in advance!

[Tored]

I have edited my post, which hopefully describes my problem more accurately now.