Migrating from RO/DA Delphi Server to Oxygene Net Core server. Second try

Elements Oxygene
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I guess you are referring to this thread: Migrating Data Abstract Delphi Server to .net console Server

The code sample in your post will leak DB connections in .NET
The rest is probable possible to implement by writing extension methods to emulate Delphi API
Also IDADataset type has no direct counterpart in .NET because Data Abstract for .NET uses native .NET DataTable and DataSet types instead